staging/android: refactor SYNC_IOC_FILE_INFO

Submitted by Gustavo Padovan on Feb. 26, 2016, 9 p.m.

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Message ID 1456520410-28195-1-git-send-email-gustavo@padovan.org
State New
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Series "Series without cover letter" ( rev: 2 ) in DRI devel

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Commit Message

Gustavo Padovan Feb. 26, 2016, 9 p.m.
From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
optimize buffer allocation. In the new approach the ioctl needs to be called
twice to retrieve the array of fence_infos pointed by info->sync_fence_info.

The first call should pass num_fences = 0, the kernel will then fill
info->num_fences. Userspace receives back the number of fences and
allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
info->sync_fence_info.

It then call the ioctl again passing num_fences received in info->num_fences.
The kernel checks if info->num_fences > 0 and if yes it fill
info->sync_fence_info with an array containing all fence_infos.

info->len now represents the length of the buffer sync_fence_info points
to. Also, info->sync_fence_info was converted to __u64 pointer.

An example userspace code would be:

	struct sync_file_info *info;
	int err, size, num_fences;

	info = malloc(sizeof(*info));

	memset(info, 0, sizeof(*info));

	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
	num_fences = info->num_fences;

	if (num_fences) {
		memset(info, 0, sizeof(*info));
		size = sizeof(struct sync_fence_info) * num_fences;
		info->len = size;
		info->num_fences = num_fences;
		info->sync_fence_info = (uint64_t) calloc(num_fences,
							  sizeof(struct sync_fence_info));

		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
	}

v2: fix fence_info memory leak

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
 drivers/staging/android/uapi/sync.h |  9 +++----
 2 files changed, 45 insertions(+), 16 deletions(-)

Patch hide | download patch | download mbox

diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
index dc5f382..2379f23 100644
--- a/drivers/staging/android/sync.c
+++ b/drivers/staging/android/sync.c
@@ -502,21 +502,22 @@  static int sync_fill_fence_info(struct fence *fence, void *data, int size)
 static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 					unsigned long arg)
 {
-	struct sync_file_info *info;
+	struct sync_file_info in, *info;
+	struct sync_fence_info *fence_info = NULL;
 	__u32 size;
 	__u32 len = 0;
 	int ret, i;
 
-	if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
+	if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
 		return -EFAULT;
 
-	if (size < sizeof(struct sync_file_info))
-		return -EINVAL;
+	if (in.status || strcmp(in.name, "\0"))
+		return -EFAULT;
 
-	if (size > 4096)
-		size = 4096;
+	if (in.num_fences && !in.sync_fence_info)
+		return -EFAULT;
 
-	info = kzalloc(size, GFP_KERNEL);
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;
 
@@ -525,14 +526,33 @@  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 	if (info->status >= 0)
 		info->status = !info->status;
 
-	info->num_fences = sync_file->num_fences;
+	/*
+	 * Passing num_fences = 0 means that userspace want to know how
+	 * many fences are in the sync_file to be able to allocate a buffer to
+	 * fit all sync_fence_infos and call the ioctl again with the buffer
+	 * assigned to info->sync_fence_info. The second call pass the
+	 * num_fences value received in the first call.
+	 */
+	if (!in.num_fences)
+		goto no_fences;
+
+	size = sync_file->num_fences * sizeof(*fence_info);
+	if (in.len != size) {
+		ret = -EFAULT;
+		goto out;
+	}
 
-	len = sizeof(struct sync_file_info);
+	fence_info = kzalloc(size, GFP_KERNEL);
+	if (!fence_info) {
+		ret = -ENOMEM;
+		goto out;
+	}
 
 	for (i = 0; i < sync_file->num_fences; ++i) {
 		struct fence *fence = sync_file->cbs[i].fence;
 
-		ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
+		ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
+					   size - len);
 
 		if (ret < 0)
 			goto out;
@@ -540,14 +560,24 @@  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 		len += ret;
 	}
 
+	if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
 	info->len = len;
+	info->sync_fence_info = (__u64) in.sync_fence_info;
+
+no_fences:
+	info->num_fences = sync_file->num_fences;
 
-	if (copy_to_user((void __user *)arg, info, len))
+	if (copy_to_user((void __user *)arg, info, sizeof(*info)))
 		ret = -EFAULT;
 	else
 		ret = 0;
 
 out:
+	kfree(fence_info);
 	kfree(info);
 
 	return ret;
diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
index f0b41ce..9aad623 100644
--- a/drivers/staging/android/uapi/sync.h
+++ b/drivers/staging/android/uapi/sync.h
@@ -42,21 +42,20 @@  struct sync_fence_info {
 
 /**
  * struct sync_file_info - data returned from fence info ioctl
- * @len:	ioctl caller writes the size of the buffer its passing in.
- *		ioctl returns length of sync_file_info returned to
- *		userspace including pt_info.
  * @name:	name of fence
  * @status:	status of fence. 1: signaled 0:active <0:error
  * @num_fences	number of fences in the sync_file
+ * @len:	ioctl caller writes the size of the buffer its passing in.
+ *		ioctl returns length of all fence_infos summed.
  * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
  */
 struct sync_file_info {
-	__u32	len;
 	char	name[32];
 	__s32	status;
 	__u32	num_fences;
+	__u32	len;
 
-	__u8	sync_fence_info[0];
+	__u64	sync_fence_info;
 };
 
 #define SYNC_IOC_MAGIC		'>'

Comments

Hi Gustavo,

On 26 February 2016 at 21:00, Gustavo Padovan <gustavo@padovan.org> wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>
> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> optimize buffer allocation. In the new approach the ioctl needs to be called
> twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
>
I might have misunderstood things but I no one says you "need" to call
it twice - you can just request a "random" amount of fences_info. Upon
return (if num_fences was non zero) it will report how many fence_info
were retrieved.

> The first call should pass num_fences = 0, the kernel will then fill
> info->num_fences. Userspace receives back the number of fences and
> allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
> info->sync_fence_info.
>
> It then call the ioctl again passing num_fences received in info->num_fences.
"calls"

> The kernel checks if info->num_fences > 0 and if yes it fill
> info->sync_fence_info with an array containing all fence_infos.
>
The above sentence sounds a bit strange. I believe you meant to say
something like "Then the kernel fills the fence_infos array with data.
One should read back the actual number from info->num_fences." ?

> info->len now represents the length of the buffer sync_fence_info points
> to.
Now that I think about it, I'm wondering if there'll be a case where
len != info->num_fences * sizeof(struct sync_file_info). If that's not
possible one could just drop len and nicely simplify things.

> Also, info->sync_fence_info was converted to __u64 pointer.
>
... pointer to prevent 32bit compatibility issues.

> An example userspace code would be:
>
>         struct sync_file_info *info;
>         int err, size, num_fences;
>
>         info = malloc(sizeof(*info));
>
>         memset(info, 0, sizeof(*info));
>
>         err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>         num_fences = info->num_fences;
>
>         if (num_fences) {
>                 memset(info, 0, sizeof(*info));
>                 size = sizeof(struct sync_fence_info) * num_fences;
>                 info->len = size;
>                 info->num_fences = num_fences;
>                 info->sync_fence_info = (uint64_t) calloc(num_fences,
>                                                           sizeof(struct sync_fence_info));
>
>                 err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>         }
>
> v2: fix fence_info memory leak
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> ---
>  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
>  drivers/staging/android/uapi/sync.h |  9 +++----
>  2 files changed, 45 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> index dc5f382..2379f23 100644
> --- a/drivers/staging/android/sync.c
> +++ b/drivers/staging/android/sync.c
> @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
>  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>                                         unsigned long arg)
>  {
> -       struct sync_file_info *info;
> +       struct sync_file_info in, *info;
> +       struct sync_fence_info *fence_info = NULL;
>         __u32 size;
>         __u32 len = 0;
>         int ret, i;
>
> -       if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
> +       if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
s/*info/in/

>                 return -EFAULT;
>
> -       if (size < sizeof(struct sync_file_info))
> -               return -EINVAL;
> +       if (in.status || strcmp(in.name, "\0"))
Afaict these two are outputs, so we should be checking them ?

> +               return -EFAULT;
>
As originally, input validation should return -EINVAL on error.


> -       if (size > 4096)
> -               size = 4096;
> +       if (in.num_fences && !in.sync_fence_info)
> +               return -EFAULT;
>
Ditto.

> -       info = kzalloc(size, GFP_KERNEL);
> +       info = kzalloc(sizeof(*info), GFP_KERNEL);
>         if (!info)
>                 return -ENOMEM;
>
> @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>         if (info->status >= 0)
>                 info->status = !info->status;
>
> -       info->num_fences = sync_file->num_fences;
> +       /*
> +        * Passing num_fences = 0 means that userspace want to know how
> +        * many fences are in the sync_file to be able to allocate a buffer to
> +        * fit all sync_fence_infos and call the ioctl again with the buffer
> +        * assigned to info->sync_fence_info. The second call pass the
> +        * num_fences value received in the first call.
> +        */
> +       if (!in.num_fences)
> +               goto no_fences;
> +
We should clamp in.num_fences to min2(in.num_fences,
sync_file->num_fences) and use it over sync_file->num_fences though
the rest of the function. Or just bail out when the two are not the
same.

Depends on what the planned semantics are. Fwiw I'm leaning towards the former.

> +       size = sync_file->num_fences * sizeof(*fence_info);
> +       if (in.len != size) {
> +               ret = -EFAULT;
EINVAL or just drop len from the struct.

> +               goto out;
> +       }
>
> -       len = sizeof(struct sync_file_info);
> +       fence_info = kzalloc(size, GFP_KERNEL);
> +       if (!fence_info) {
> +               ret = -ENOMEM;
> +               goto out;
> +       }
>
>         for (i = 0; i < sync_file->num_fences; ++i) {
>                 struct fence *fence = sync_file->cbs[i].fence;
>
> -               ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
> +               ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
A few comments about sync_fill_fence_info()
 - Internal function so make the second argument of the correct type -
struct sync_fence_info *
 - Drop the third argument size, as that one is always sizeof(sync_fence_info).
 - Remove the size checking in the same function and make its return type void

Then one can simplify this loop even further :-)

> +                                          size - len);
>
>                 if (ret < 0)
>                         goto out;
> @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>                 len += ret;
>         }
>
> +       if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
> +               ret = -EFAULT;
> +               goto out;
> +       }
> +
>         info->len = len;
> +       info->sync_fence_info = (__u64) in.sync_fence_info;
Why the cast ?

> +
> +no_fences:
> +       info->num_fences = sync_file->num_fences;
>
> -       if (copy_to_user((void __user *)arg, info, len))
> +       if (copy_to_user((void __user *)arg, info, sizeof(*info)))
Don't know if we should be returning (copying) any other information
but info->num_fences in case of "no_fences". In case it's not clear -
I'm thinking about the data we already have in in info->name and
info->status.

Regards,
Emil
Hi Emil,

2016-02-27 Emil Velikov <emil.l.velikov@gmail.com>:

> Hi Gustavo,
> 
> On 26 February 2016 at 21:00, Gustavo Padovan <gustavo@padovan.org> wrote:
> > From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> >
> > Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> > optimize buffer allocation. In the new approach the ioctl needs to be called
> > twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
> >
> I might have misunderstood things but I no one says you "need" to call
> it twice - you can just request a "random" amount of fences_info. Upon
> return (if num_fences was non zero) it will report how many fence_info
> were retrieved.

Right, I don't see any problem doing it in one request, I just didn't 
think about that in the new proposal. I'll update the code and commit
message accordinly.

> 
> > The first call should pass num_fences = 0, the kernel will then fill
> > info->num_fences. Userspace receives back the number of fences and
> > allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
> > info->sync_fence_info.
> >
> > It then call the ioctl again passing num_fences received in info->num_fences.
> "calls"
> 
> > The kernel checks if info->num_fences > 0 and if yes it fill
> > info->sync_fence_info with an array containing all fence_infos.
> >
> The above sentence sounds a bit strange. I believe you meant to say
> something like "Then the kernel fills the fence_infos array with data.
> One should read back the actual number from info->num_fences." ?
> 
> > info->len now represents the length of the buffer sync_fence_info points
> > to.
> Now that I think about it, I'm wondering if there'll be a case where
> len != info->num_fences * sizeof(struct sync_file_info). If that's not
> possible one could just drop len and nicely simplify things.
> 
> > Also, info->sync_fence_info was converted to __u64 pointer.
> >
> ... pointer to prevent 32bit compatibility issues.
> 
> > An example userspace code would be:
> >
> >         struct sync_file_info *info;
> >         int err, size, num_fences;
> >
> >         info = malloc(sizeof(*info));
> >
> >         memset(info, 0, sizeof(*info));
> >
> >         err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> >         num_fences = info->num_fences;
> >
> >         if (num_fences) {
> >                 memset(info, 0, sizeof(*info));
> >                 size = sizeof(struct sync_fence_info) * num_fences;
> >                 info->len = size;
> >                 info->num_fences = num_fences;
> >                 info->sync_fence_info = (uint64_t) calloc(num_fences,
> >                                                           sizeof(struct sync_fence_info));
> >
> >                 err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> >         }
> >
> > v2: fix fence_info memory leak
> >
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> > ---
> >  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
> >  drivers/staging/android/uapi/sync.h |  9 +++----
> >  2 files changed, 45 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> > index dc5f382..2379f23 100644
> > --- a/drivers/staging/android/sync.c
> > +++ b/drivers/staging/android/sync.c
> > @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
> >  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >                                         unsigned long arg)
> >  {
> > -       struct sync_file_info *info;
> > +       struct sync_file_info in, *info;
> > +       struct sync_fence_info *fence_info = NULL;
> >         __u32 size;
> >         __u32 len = 0;
> >         int ret, i;
> >
> > -       if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
> > +       if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
> s/*info/in/
> 
> >                 return -EFAULT;
> >
> > -       if (size < sizeof(struct sync_file_info))
> > -               return -EINVAL;
> > +       if (in.status || strcmp(in.name, "\0"))
> Afaict these two are outputs, so we should be checking them ?

Hmm. Maybe not.

> 
> > +               return -EFAULT;
> >
> As originally, input validation should return -EINVAL on error.
> 
> 
> > -       if (size > 4096)
> > -               size = 4096;
> > +       if (in.num_fences && !in.sync_fence_info)
> > +               return -EFAULT;
> >
> Ditto.
> 
> > -       info = kzalloc(size, GFP_KERNEL);
> > +       info = kzalloc(sizeof(*info), GFP_KERNEL);
> >         if (!info)
> >                 return -ENOMEM;
> >
> > @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >         if (info->status >= 0)
> >                 info->status = !info->status;
> >
> > -       info->num_fences = sync_file->num_fences;
> > +       /*
> > +        * Passing num_fences = 0 means that userspace want to know how
> > +        * many fences are in the sync_file to be able to allocate a buffer to
> > +        * fit all sync_fence_infos and call the ioctl again with the buffer
> > +        * assigned to info->sync_fence_info. The second call pass the
> > +        * num_fences value received in the first call.
> > +        */
> > +       if (!in.num_fences)
> > +               goto no_fences;
> > +
> We should clamp in.num_fences to min2(in.num_fences,
> sync_file->num_fences) and use it over sync_file->num_fences though
> the rest of the function. Or just bail out when the two are not the
> same.
> 
> Depends on what the planned semantics are. Fwiw I'm leaning towards the former.

If num_fences received is smaller than the actual num_fences I think we
should fails, otherwise we should just fill the buffer with all
fence_infos...

> 
> > +       size = sync_file->num_fences * sizeof(*fence_info);
> > +       if (in.len != size) {
> > +               ret = -EFAULT;
> EINVAL or just drop len from the struct.

...so this check now would be in.len < size.

> 
> > +               goto out;
> > +       }
> >
> > -       len = sizeof(struct sync_file_info);
> > +       fence_info = kzalloc(size, GFP_KERNEL);
> > +       if (!fence_info) {
> > +               ret = -ENOMEM;
> > +               goto out;
> > +       }
> >
> >         for (i = 0; i < sync_file->num_fences; ++i) {
> >                 struct fence *fence = sync_file->cbs[i].fence;
> >
> > -               ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
> > +               ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
> A few comments about sync_fill_fence_info()
>  - Internal function so make the second argument of the correct type -
> struct sync_fence_info *
>  - Drop the third argument size, as that one is always sizeof(sync_fence_info).
>  - Remove the size checking in the same function and make its return type void
> 
> Then one can simplify this loop even further :-)

Sounds good to me.

> 
> > +                                          size - len);
> >
> >                 if (ret < 0)
> >                         goto out;
> > @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >                 len += ret;
> >         }
> >
> > +       if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
> > +               ret = -EFAULT;
> > +               goto out;
> > +       }
> > +
> >         info->len = len;
> > +       info->sync_fence_info = (__u64) in.sync_fence_info;
> Why the cast ?
> 
> > +
> > +no_fences:
> > +       info->num_fences = sync_file->num_fences;
> >
> > -       if (copy_to_user((void __user *)arg, info, len))
> > +       if (copy_to_user((void __user *)arg, info, sizeof(*info)))
> Don't know if we should be returning (copying) any other information
> but info->num_fences in case of "no_fences". In case it's not clear -
> I'm thinking about the data we already have in in info->name and
> info->status.

Userspace might want to know all info about the sync_file but
sync_fence_info.

	Gustavo
Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>
> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> optimize buffer allocation. In the new approach the ioctl needs to be called
> twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
>
> The first call should pass num_fences = 0, the kernel will then fill
> info->num_fences. Userspace receives back the number of fences and
> allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
> info->sync_fence_info.
>
> It then call the ioctl again passing num_fences received in info->num_fences.
> The kernel checks if info->num_fences > 0 and if yes it fill
> info->sync_fence_info with an array containing all fence_infos.
>
> info->len now represents the length of the buffer sync_fence_info points
> to. Also, info->sync_fence_info was converted to __u64 pointer.
>
> An example userspace code would be:
>
> 	struct sync_file_info *info;
> 	int err, size, num_fences;
>
> 	info = malloc(sizeof(*info));
>
> 	memset(info, 0, sizeof(*info));
>
> 	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> 	num_fences = info->num_fences;
>
> 	if (num_fences) {
> 		memset(info, 0, sizeof(*info));
Would this memset still be needed if we didn't check for nulls in info->status and info->name ?

Seems to me that it could be skipped in that case.
> 		size = sizeof(struct sync_fence_info) * num_fences;
> 		info->len = size;
> 		info->num_fences = num_fences;
> 		info->sync_fence_info = (uint64_t) calloc(num_fences,
> 							  sizeof(struct sync_fence_info));
>
> 		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> 	}
>
> v2: fix fence_info memory leak
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> ---
>  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
>  drivers/staging/android/uapi/sync.h |  9 +++----
>  2 files changed, 45 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> index dc5f382..2379f23 100644
> --- a/drivers/staging/android/sync.c
> +++ b/drivers/staging/android/sync.c
> @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
>  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>  					unsigned long arg)
>  {
> -	struct sync_file_info *info;
> +	struct sync_file_info in, *info;
> +	struct sync_fence_info *fence_info = NULL;
>  	__u32 size;
>  	__u32 len = 0;
= 0 unneeded.
>  	int ret, i;
>  
> -	if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
> +	if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
>  		return -EFAULT;
>  
> -	if (size < sizeof(struct sync_file_info))
> -		return -EINVAL;
> +	if (in.status || strcmp(in.name, "\0"))
> +		return -EFAULT;
These members always get written by the fence ioctl, I'm not sure it adds value to have them explicitly zero'd out by userspace.
> -	if (size > 4096)
> -		size = 4096;
> +	if (in.num_fences && !in.sync_fence_info)
> +		return -EFAULT;
This check is unneeded, it will happen in the copy_to_user call anyway.
> -	info = kzalloc(size, GFP_KERNEL);
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
>  	if (!info)
>  		return -ENOMEM;
>  
> @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>  	if (info->status >= 0)
>  		info->status = !info->status;
>  
> -	info->num_fences = sync_file->num_fences;
> +	/*
> +	 * Passing num_fences = 0 means that userspace want to know how
> +	 * many fences are in the sync_file to be able to allocate a buffer to
> +	 * fit all sync_fence_infos and call the ioctl again with the buffer
> +	 * assigned to info->sync_fence_info. The second call pass the
> +	 * num_fences value received in the first call.
> +	 */
> +	if (!in.num_fences)
> +		goto no_fences;
> +
> +	size = sync_file->num_fences * sizeof(*fence_info);
> +	if (in.len != size) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
Maybe check for in.len < size, and set set to size?


> -	len = sizeof(struct sync_file_info);
> +	fence_info = kzalloc(size, GFP_KERNEL);
> +	if (!fence_info) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  
>  	for (i = 0; i < sync_file->num_fences; ++i) {
>  		struct fence *fence = sync_file->cbs[i].fence;
>  
> -		ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
> +		ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
> +					   size - len);
>  
>  		if (ret < 0)
>  			goto out;
> @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>  		len += ret;
>  	}
>  
> +	if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
>  	info->len = len;
> +	info->sync_fence_info = (__u64) in.sync_fence_info;
> +
> +no_fences:
> +	info->num_fences = sync_file->num_fences;
>  
> -	if (copy_to_user((void __user *)arg, info, len))
> +	if (copy_to_user((void __user *)arg, info, sizeof(*info)))
>  		ret = -EFAULT;
>  	else
>  		ret = 0;
>  
>  out:
> +	kfree(fence_info);
>  	kfree(info);
>  
>  	return ret;
> diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
> index f0b41ce..9aad623 100644
> --- a/drivers/staging/android/uapi/sync.h
> +++ b/drivers/staging/android/uapi/sync.h
> @@ -42,21 +42,20 @@ struct sync_fence_info {
>  
>  /**
>   * struct sync_file_info - data returned from fence info ioctl
> - * @len:	ioctl caller writes the size of the buffer its passing in.
> - *		ioctl returns length of sync_file_info returned to
> - *		userspace including pt_info.
>   * @name:	name of fence
>   * @status:	status of fence. 1: signaled 0:active <0:error
>   * @num_fences	number of fences in the sync_file
> + * @len:	ioctl caller writes the size of the buffer its passing in.
> + *		ioctl returns length of all fence_infos summed.
>   * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
>   */
>  struct sync_file_info {
> -	__u32	len;
>  	char	name[32];
>  	__s32	status;
>  	__u32	num_fences;
> +	__u32	len;
>  
> -	__u8	sync_fence_info[0];
> +	__u64	sync_fence_info;
>  };
>  
>  #define SYNC_IOC_MAGIC		'>'
Not sure if len adds anything here, userspace knows to allocate num_fences * sizeof(struct sync_fence_info);

It could probably be removed since num_fences would do the same.

~Maarten
Hi Gustavo,

On 27 February 2016 at 15:25, Gustavo Padovan
<gustavo.padovan@collabora.co.uk> wrote:
> Hi Emil,
>
> 2016-02-27 Emil Velikov <emil.l.velikov@gmail.com>:
>
>> Hi Gustavo,
>>
>> On 26 February 2016 at 21:00, Gustavo Padovan <gustavo@padovan.org> wrote:
>> > From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>> >
>> > Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
>> > optimize buffer allocation. In the new approach the ioctl needs to be called
>> > twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
>> >
>> I might have misunderstood things but I no one says you "need" to call
>> it twice - you can just request a "random" amount of fences_info. Upon
>> return (if num_fences was non zero) it will report how many fence_info
>> were retrieved.
>
> Right, I don't see any problem doing it in one request, I just didn't
> think about that in the new proposal. I'll update the code and commit
> message accordinly.
>
>>
>> > The first call should pass num_fences = 0, the kernel will then fill
>> > info->num_fences. Userspace receives back the number of fences and
>> > allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
>> > info->sync_fence_info.
>> >
>> > It then call the ioctl again passing num_fences received in info->num_fences.
>> "calls"
>>
>> > The kernel checks if info->num_fences > 0 and if yes it fill
>> > info->sync_fence_info with an array containing all fence_infos.
>> >
>> The above sentence sounds a bit strange. I believe you meant to say
>> something like "Then the kernel fills the fence_infos array with data.
>> One should read back the actual number from info->num_fences." ?
>>
>> > info->len now represents the length of the buffer sync_fence_info points
>> > to.
>> Now that I think about it, I'm wondering if there'll be a case where
>> len != info->num_fences * sizeof(struct sync_file_info). If that's not
>> possible one could just drop len and nicely simplify things.
>>
>> > Also, info->sync_fence_info was converted to __u64 pointer.
>> >
>> ... pointer to prevent 32bit compatibility issues.
>>
>> > An example userspace code would be:
>> >
>> >         struct sync_file_info *info;
>> >         int err, size, num_fences;
>> >
>> >         info = malloc(sizeof(*info));
>> >
>> >         memset(info, 0, sizeof(*info));
>> >
>> >         err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>> >         num_fences = info->num_fences;
>> >
>> >         if (num_fences) {
>> >                 memset(info, 0, sizeof(*info));
>> >                 size = sizeof(struct sync_fence_info) * num_fences;
>> >                 info->len = size;
>> >                 info->num_fences = num_fences;
>> >                 info->sync_fence_info = (uint64_t) calloc(num_fences,
>> >                                                           sizeof(struct sync_fence_info));
>> >
>> >                 err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>> >         }
>> >
>> > v2: fix fence_info memory leak
>> >
>> > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>> > ---
>> >  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
>> >  drivers/staging/android/uapi/sync.h |  9 +++----
>> >  2 files changed, 45 insertions(+), 16 deletions(-)
>> >
>> > diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
>> > index dc5f382..2379f23 100644
>> > --- a/drivers/staging/android/sync.c
>> > +++ b/drivers/staging/android/sync.c
>> > @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
>> >  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>> >                                         unsigned long arg)
>> >  {
>> > -       struct sync_file_info *info;
>> > +       struct sync_file_info in, *info;
>> > +       struct sync_fence_info *fence_info = NULL;
>> >         __u32 size;
>> >         __u32 len = 0;
>> >         int ret, i;
>> >
>> > -       if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
>> > +       if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
>> s/*info/in/
>>
>> >                 return -EFAULT;
>> >
>> > -       if (size < sizeof(struct sync_file_info))
>> > -               return -EINVAL;
>> > +       if (in.status || strcmp(in.name, "\0"))
>> Afaict these two are outputs, so we should be checking them ?
>
> Hmm. Maybe not.
>
>>
>> > +               return -EFAULT;
>> >
>> As originally, input validation should return -EINVAL on error.
>>
>>
>> > -       if (size > 4096)
>> > -               size = 4096;
>> > +       if (in.num_fences && !in.sync_fence_info)
>> > +               return -EFAULT;
>> >
>> Ditto.
>>
>> > -       info = kzalloc(size, GFP_KERNEL);
>> > +       info = kzalloc(sizeof(*info), GFP_KERNEL);
>> >         if (!info)
>> >                 return -ENOMEM;
>> >
>> > @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>> >         if (info->status >= 0)
>> >                 info->status = !info->status;
>> >
>> > -       info->num_fences = sync_file->num_fences;
>> > +       /*
>> > +        * Passing num_fences = 0 means that userspace want to know how
>> > +        * many fences are in the sync_file to be able to allocate a buffer to
>> > +        * fit all sync_fence_infos and call the ioctl again with the buffer
>> > +        * assigned to info->sync_fence_info. The second call pass the
>> > +        * num_fences value received in the first call.
>> > +        */
>> > +       if (!in.num_fences)
>> > +               goto no_fences;
>> > +
>> We should clamp in.num_fences to min2(in.num_fences,
>> sync_file->num_fences) and use it over sync_file->num_fences though
>> the rest of the function. Or just bail out when the two are not the
>> same.
>>
>> Depends on what the planned semantics are. Fwiw I'm leaning towards the former.
>
> If num_fences received is smaller than the actual num_fences I think we
> should fails, otherwise we should just fill the buffer with all
> fence_infos...
>
Fair enough. Just make sure that this is clearly explained to the use
- manpages, other ?

>>
>> > +       size = sync_file->num_fences * sizeof(*fence_info);
>> > +       if (in.len != size) {
>> > +               ret = -EFAULT;
>> EINVAL or just drop len from the struct.
>
> ...so this check now would be in.len < size.
>
>>
>> > +               goto out;
>> > +       }
>> >
>> > -       len = sizeof(struct sync_file_info);
>> > +       fence_info = kzalloc(size, GFP_KERNEL);
>> > +       if (!fence_info) {
>> > +               ret = -ENOMEM;
>> > +               goto out;
>> > +       }
>> >
>> >         for (i = 0; i < sync_file->num_fences; ++i) {
>> >                 struct fence *fence = sync_file->cbs[i].fence;
>> >
>> > -               ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
>> > +               ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
>> A few comments about sync_fill_fence_info()
>>  - Internal function so make the second argument of the correct type -
>> struct sync_fence_info *
>>  - Drop the third argument size, as that one is always sizeof(sync_fence_info).
>>  - Remove the size checking in the same function and make its return type void
>>
>> Then one can simplify this loop even further :-)
>
> Sounds good to me.
>
>>
>> > +                                          size - len);
>> >
>> >                 if (ret < 0)
>> >                         goto out;
>> > @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>> >                 len += ret;
>> >         }
>> >
>> > +       if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
>> > +               ret = -EFAULT;
>> > +               goto out;
>> > +       }
>> > +
>> >         info->len = len;
>> > +       info->sync_fence_info = (__u64) in.sync_fence_info;
>> Why the cast ?
>>
>> > +
>> > +no_fences:
>> > +       info->num_fences = sync_file->num_fences;
>> >
>> > -       if (copy_to_user((void __user *)arg, info, len))
>> > +       if (copy_to_user((void __user *)arg, info, sizeof(*info)))
>> Don't know if we should be returning (copying) any other information
>> but info->num_fences in case of "no_fences". In case it's not clear -
>> I'm thinking about the data we already have in in info->name and
>> info->status.
>
> Userspace might want to know all info about the sync_file but
> sync_fence_info.
>
IMHO, that does sound like a rather strange use of the API. Whichever
route one goes for, it would be nice to have the behaviour clearly
documented. Otherwise things will end up quite confusing.
Documentation can be done in separate patch/series.

Thanks
Emil
Hi Maarten,

2016-02-29 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:

> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> > From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> >
> > Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> > optimize buffer allocation. In the new approach the ioctl needs to be called
> > twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
> >
> > The first call should pass num_fences = 0, the kernel will then fill
> > info->num_fences. Userspace receives back the number of fences and
> > allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
> > info->sync_fence_info.
> >
> > It then call the ioctl again passing num_fences received in info->num_fences.
> > The kernel checks if info->num_fences > 0 and if yes it fill
> > info->sync_fence_info with an array containing all fence_infos.
> >
> > info->len now represents the length of the buffer sync_fence_info points
> > to. Also, info->sync_fence_info was converted to __u64 pointer.
> >
> > An example userspace code would be:
> >
> > 	struct sync_file_info *info;
> > 	int err, size, num_fences;
> >
> > 	info = malloc(sizeof(*info));
> >
> > 	memset(info, 0, sizeof(*info));
> >
> > 	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> > 	num_fences = info->num_fences;
> >
> > 	if (num_fences) {
> > 		memset(info, 0, sizeof(*info));
> Would this memset still be needed if we didn't check for nulls in info->status and info->name ?
> 
> Seems to me that it could be skipped in that case.

Yes, I agree.

> > 		size = sizeof(struct sync_fence_info) * num_fences;
> > 		info->len = size;
> > 		info->num_fences = num_fences;
> > 		info->sync_fence_info = (uint64_t) calloc(num_fences,
> > 							  sizeof(struct sync_fence_info));
> >
> > 		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> > 	}
> >
> > v2: fix fence_info memory leak
> >
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> > ---
> >  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
> >  drivers/staging/android/uapi/sync.h |  9 +++----
> >  2 files changed, 45 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> > index dc5f382..2379f23 100644
> > --- a/drivers/staging/android/sync.c
> > +++ b/drivers/staging/android/sync.c
> > @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
> >  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >  					unsigned long arg)
> >  {
> > -	struct sync_file_info *info;
> > +	struct sync_file_info in, *info;
> > +	struct sync_fence_info *fence_info = NULL;
> >  	__u32 size;
> >  	__u32 len = 0;
> = 0 unneeded.
> >  	int ret, i;
> >  
> > -	if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
> > +	if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
> >  		return -EFAULT;
> >  
> > -	if (size < sizeof(struct sync_file_info))
> > -		return -EINVAL;
> > +	if (in.status || strcmp(in.name, "\0"))
> > +		return -EFAULT;
> These members always get written by the fence ioctl, I'm not sure it adds value to have them explicitly zero'd out by userspace.
> > -	if (size > 4096)
> > -		size = 4096;
> > +	if (in.num_fences && !in.sync_fence_info)
> > +		return -EFAULT;
> This check is unneeded, it will happen in the copy_to_user call anyway.
> > -	info = kzalloc(size, GFP_KERNEL);
> > +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> >  	if (!info)
> >  		return -ENOMEM;
> >  
> > @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >  	if (info->status >= 0)
> >  		info->status = !info->status;
> >  
> > -	info->num_fences = sync_file->num_fences;
> > +	/*
> > +	 * Passing num_fences = 0 means that userspace want to know how
> > +	 * many fences are in the sync_file to be able to allocate a buffer to
> > +	 * fit all sync_fence_infos and call the ioctl again with the buffer
> > +	 * assigned to info->sync_fence_info. The second call pass the
> > +	 * num_fences value received in the first call.
> > +	 */
> > +	if (!in.num_fences)
> > +		goto no_fences;
> > +
> > +	size = sync_file->num_fences * sizeof(*fence_info);
> > +	if (in.len != size) {
> > +		ret = -EFAULT;
> > +		goto out;
> > +	}
> Maybe check for in.len < size, and set set to size?
> 
> 
> > -	len = sizeof(struct sync_file_info);
> > +	fence_info = kzalloc(size, GFP_KERNEL);
> > +	if (!fence_info) {
> > +		ret = -ENOMEM;
> > +		goto out;
> > +	}
> >  
> >  	for (i = 0; i < sync_file->num_fences; ++i) {
> >  		struct fence *fence = sync_file->cbs[i].fence;
> >  
> > -		ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
> > +		ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
> > +					   size - len);
> >  
> >  		if (ret < 0)
> >  			goto out;
> > @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >  		len += ret;
> >  	}
> >  
> > +	if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
> > +		ret = -EFAULT;
> > +		goto out;
> > +	}
> > +
> >  	info->len = len;
> > +	info->sync_fence_info = (__u64) in.sync_fence_info;
> > +
> > +no_fences:
> > +	info->num_fences = sync_file->num_fences;
> >  
> > -	if (copy_to_user((void __user *)arg, info, len))
> > +	if (copy_to_user((void __user *)arg, info, sizeof(*info)))
> >  		ret = -EFAULT;
> >  	else
> >  		ret = 0;
> >  
> >  out:
> > +	kfree(fence_info);
> >  	kfree(info);
> >  
> >  	return ret;
> > diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
> > index f0b41ce..9aad623 100644
> > --- a/drivers/staging/android/uapi/sync.h
> > +++ b/drivers/staging/android/uapi/sync.h
> > @@ -42,21 +42,20 @@ struct sync_fence_info {
> >  
> >  /**
> >   * struct sync_file_info - data returned from fence info ioctl
> > - * @len:	ioctl caller writes the size of the buffer its passing in.
> > - *		ioctl returns length of sync_file_info returned to
> > - *		userspace including pt_info.
> >   * @name:	name of fence
> >   * @status:	status of fence. 1: signaled 0:active <0:error
> >   * @num_fences	number of fences in the sync_file
> > + * @len:	ioctl caller writes the size of the buffer its passing in.
> > + *		ioctl returns length of all fence_infos summed.
> >   * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
> >   */
> >  struct sync_file_info {
> > -	__u32	len;
> >  	char	name[32];
> >  	__s32	status;
> >  	__u32	num_fences;
> > +	__u32	len;
> >  
> > -	__u8	sync_fence_info[0];
> > +	__u64	sync_fence_info;
> >  };
> >  
> >  #define SYNC_IOC_MAGIC		'>'
> Not sure if len adds anything here, userspace knows to allocate num_fences * sizeof(struct sync_fence_info);

I think of len being useful if we decide to extend struct sync_fence_info in
the future, so we may use len to help discover the size of each
sync_fence_info. What do you think?

	Gustavo
Op 29-02-16 om 23:08 schreef Gustavo Padovan:
> Hi Maarten,
>
> 2016-02-29 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:
>
>> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
>>> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>>>
>>> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
>>> optimize buffer allocation. In the new approach the ioctl needs to be called
>>> twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
>>>
>>> The first call should pass num_fences = 0, the kernel will then fill
>>> info->num_fences. Userspace receives back the number of fences and
>>> allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
>>> info->sync_fence_info.
>>>
>>> It then call the ioctl again passing num_fences received in info->num_fences.
>>> The kernel checks if info->num_fences > 0 and if yes it fill
>>> info->sync_fence_info with an array containing all fence_infos.
>>>
>>> info->len now represents the length of the buffer sync_fence_info points
>>> to. Also, info->sync_fence_info was converted to __u64 pointer.
>>>
>>> An example userspace code would be:
>>>
>>> 	struct sync_file_info *info;
>>> 	int err, size, num_fences;
>>>
>>> 	info = malloc(sizeof(*info));
>>>
>>> 	memset(info, 0, sizeof(*info));
>>>
>>> 	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>>> 	num_fences = info->num_fences;
>>>
>>> 	if (num_fences) {
>>> 		memset(info, 0, sizeof(*info));
>> Would this memset still be needed if we didn't check for nulls in info->status and info->name ?
>>
>> Seems to me that it could be skipped in that case.
> Yes, I agree.
>
>>> 		size = sizeof(struct sync_fence_info) * num_fences;
>>> 		info->len = size;
>>> 		info->num_fences = num_fences;
>>> 		info->sync_fence_info = (uint64_t) calloc(num_fences,
>>> 							  sizeof(struct sync_fence_info));
>>>
>>> 		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
>>> 	}
>>>
>>> v2: fix fence_info memory leak
>>>
>>> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>>> ---
>>>  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
>>>  drivers/staging/android/uapi/sync.h |  9 +++----
>>>  2 files changed, 45 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
>>> index dc5f382..2379f23 100644
>>> --- a/drivers/staging/android/sync.c
>>> +++ b/drivers/staging/android/sync.c
>>> @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
>>>  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>>>  					unsigned long arg)
>>>  {
>>> -	struct sync_file_info *info;
>>> +	struct sync_file_info in, *info;
>>> +	struct sync_fence_info *fence_info = NULL;
>>>  	__u32 size;
>>>  	__u32 len = 0;
>> = 0 unneeded.
>>>  	int ret, i;
>>>  
>>> -	if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
>>> +	if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
>>>  		return -EFAULT;
>>>  
>>> -	if (size < sizeof(struct sync_file_info))
>>> -		return -EINVAL;
>>> +	if (in.status || strcmp(in.name, "\0"))
>>> +		return -EFAULT;
>> These members always get written by the fence ioctl, I'm not sure it adds value to have them explicitly zero'd out by userspace.
>>> -	if (size > 4096)
>>> -		size = 4096;
>>> +	if (in.num_fences && !in.sync_fence_info)
>>> +		return -EFAULT;
>> This check is unneeded, it will happen in the copy_to_user call anyway.
>>> -	info = kzalloc(size, GFP_KERNEL);
>>> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
>>>  	if (!info)
>>>  		return -ENOMEM;
>>>  
>>> @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>>>  	if (info->status >= 0)
>>>  		info->status = !info->status;
>>>  
>>> -	info->num_fences = sync_file->num_fences;
>>> +	/*
>>> +	 * Passing num_fences = 0 means that userspace want to know how
>>> +	 * many fences are in the sync_file to be able to allocate a buffer to
>>> +	 * fit all sync_fence_infos and call the ioctl again with the buffer
>>> +	 * assigned to info->sync_fence_info. The second call pass the
>>> +	 * num_fences value received in the first call.
>>> +	 */
>>> +	if (!in.num_fences)
>>> +		goto no_fences;
>>> +
>>> +	size = sync_file->num_fences * sizeof(*fence_info);
>>> +	if (in.len != size) {
>>> +		ret = -EFAULT;
>>> +		goto out;
>>> +	}
>> Maybe check for in.len < size, and set set to size?
>>
>>
>>> -	len = sizeof(struct sync_file_info);
>>> +	fence_info = kzalloc(size, GFP_KERNEL);
>>> +	if (!fence_info) {
>>> +		ret = -ENOMEM;
>>> +		goto out;
>>> +	}
>>>  
>>>  	for (i = 0; i < sync_file->num_fences; ++i) {
>>>  		struct fence *fence = sync_file->cbs[i].fence;
>>>  
>>> -		ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
>>> +		ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
>>> +					   size - len);
>>>  
>>>  		if (ret < 0)
>>>  			goto out;
>>> @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
>>>  		len += ret;
>>>  	}
>>>  
>>> +	if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
>>> +		ret = -EFAULT;
>>> +		goto out;
>>> +	}
>>> +
>>>  	info->len = len;
>>> +	info->sync_fence_info = (__u64) in.sync_fence_info;
>>> +
>>> +no_fences:
>>> +	info->num_fences = sync_file->num_fences;
>>>  
>>> -	if (copy_to_user((void __user *)arg, info, len))
>>> +	if (copy_to_user((void __user *)arg, info, sizeof(*info)))
>>>  		ret = -EFAULT;
>>>  	else
>>>  		ret = 0;
>>>  
>>>  out:
>>> +	kfree(fence_info);
>>>  	kfree(info);
>>>  
>>>  	return ret;
>>> diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
>>> index f0b41ce..9aad623 100644
>>> --- a/drivers/staging/android/uapi/sync.h
>>> +++ b/drivers/staging/android/uapi/sync.h
>>> @@ -42,21 +42,20 @@ struct sync_fence_info {
>>>  
>>>  /**
>>>   * struct sync_file_info - data returned from fence info ioctl
>>> - * @len:	ioctl caller writes the size of the buffer its passing in.
>>> - *		ioctl returns length of sync_file_info returned to
>>> - *		userspace including pt_info.
>>>   * @name:	name of fence
>>>   * @status:	status of fence. 1: signaled 0:active <0:error
>>>   * @num_fences	number of fences in the sync_file
>>> + * @len:	ioctl caller writes the size of the buffer its passing in.
>>> + *		ioctl returns length of all fence_infos summed.
>>>   * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
>>>   */
>>>  struct sync_file_info {
>>> -	__u32	len;
>>>  	char	name[32];
>>>  	__s32	status;
>>>  	__u32	num_fences;
>>> +	__u32	len;
>>>  
>>> -	__u8	sync_fence_info[0];
>>> +	__u64	sync_fence_info;
>>>  };
>>>  
>>>  #define SYNC_IOC_MAGIC		'>'
>> Not sure if len adds anything here, userspace knows to allocate num_fences * sizeof(struct sync_fence_info);
> I think of len being useful if we decide to extend struct sync_fence_info in
> the future, so we may use len to help discover the size of each
> sync_fence_info. What do you think?
>
I don't think you could extend it arbitrarily, you could make userspace pass a flag to indicate the struct is extended, so kernel space can choose
whether to use the bigger size struct or not.

something like sync_file_info.flags = FENCE_INFO_V2; -- kernel can reject with -EINVAL if unsupported, or fill in a v2 struct.

~Maarten
Hi Maarten,

2016-03-01 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:

> Op 29-02-16 om 23:08 schreef Gustavo Padovan:
> > Hi Maarten,
> >
> > 2016-02-29 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:
> >
> >> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> >>> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> >>>
> >>> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> >>> optimize buffer allocation. In the new approach the ioctl needs to be called
> >>> twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
> >>>
> >>> The first call should pass num_fences = 0, the kernel will then fill
> >>> info->num_fences. Userspace receives back the number of fences and
> >>> allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
> >>> info->sync_fence_info.
> >>>
> >>> It then call the ioctl again passing num_fences received in info->num_fences.
> >>> The kernel checks if info->num_fences > 0 and if yes it fill
> >>> info->sync_fence_info with an array containing all fence_infos.
> >>>
> >>> info->len now represents the length of the buffer sync_fence_info points
> >>> to. Also, info->sync_fence_info was converted to __u64 pointer.
> >>>
> >>> An example userspace code would be:
> >>>
> >>> 	struct sync_file_info *info;
> >>> 	int err, size, num_fences;
> >>>
> >>> 	info = malloc(sizeof(*info));
> >>>
> >>> 	memset(info, 0, sizeof(*info));
> >>>
> >>> 	err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> >>> 	num_fences = info->num_fences;
> >>>
> >>> 	if (num_fences) {
> >>> 		memset(info, 0, sizeof(*info));
> >> Would this memset still be needed if we didn't check for nulls in info->status and info->name ?
> >>
> >> Seems to me that it could be skipped in that case.
> > Yes, I agree.
> >
> >>> 		size = sizeof(struct sync_fence_info) * num_fences;
> >>> 		info->len = size;
> >>> 		info->num_fences = num_fences;
> >>> 		info->sync_fence_info = (uint64_t) calloc(num_fences,
> >>> 							  sizeof(struct sync_fence_info));
> >>>
> >>> 		err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> >>> 	}
> >>>
> >>> v2: fix fence_info memory leak
> >>>
> >>> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> >>> ---
> >>>  drivers/staging/android/sync.c      | 52 +++++++++++++++++++++++++++++--------
> >>>  drivers/staging/android/uapi/sync.h |  9 +++----
> >>>  2 files changed, 45 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> >>> index dc5f382..2379f23 100644
> >>> --- a/drivers/staging/android/sync.c
> >>> +++ b/drivers/staging/android/sync.c
> >>> @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
> >>>  static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >>>  					unsigned long arg)
> >>>  {
> >>> -	struct sync_file_info *info;
> >>> +	struct sync_file_info in, *info;
> >>> +	struct sync_fence_info *fence_info = NULL;
> >>>  	__u32 size;
> >>>  	__u32 len = 0;
> >> = 0 unneeded.
> >>>  	int ret, i;
> >>>  
> >>> -	if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
> >>> +	if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
> >>>  		return -EFAULT;
> >>>  
> >>> -	if (size < sizeof(struct sync_file_info))
> >>> -		return -EINVAL;
> >>> +	if (in.status || strcmp(in.name, "\0"))
> >>> +		return -EFAULT;
> >> These members always get written by the fence ioctl, I'm not sure it adds value to have them explicitly zero'd out by userspace.
> >>> -	if (size > 4096)
> >>> -		size = 4096;
> >>> +	if (in.num_fences && !in.sync_fence_info)
> >>> +		return -EFAULT;
> >> This check is unneeded, it will happen in the copy_to_user call anyway.
> >>> -	info = kzalloc(size, GFP_KERNEL);
> >>> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> >>>  	if (!info)
> >>>  		return -ENOMEM;
> >>>  
> >>> @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >>>  	if (info->status >= 0)
> >>>  		info->status = !info->status;
> >>>  
> >>> -	info->num_fences = sync_file->num_fences;
> >>> +	/*
> >>> +	 * Passing num_fences = 0 means that userspace want to know how
> >>> +	 * many fences are in the sync_file to be able to allocate a buffer to
> >>> +	 * fit all sync_fence_infos and call the ioctl again with the buffer
> >>> +	 * assigned to info->sync_fence_info. The second call pass the
> >>> +	 * num_fences value received in the first call.
> >>> +	 */
> >>> +	if (!in.num_fences)
> >>> +		goto no_fences;
> >>> +
> >>> +	size = sync_file->num_fences * sizeof(*fence_info);
> >>> +	if (in.len != size) {
> >>> +		ret = -EFAULT;
> >>> +		goto out;
> >>> +	}
> >> Maybe check for in.len < size, and set set to size?
> >>
> >>
> >>> -	len = sizeof(struct sync_file_info);
> >>> +	fence_info = kzalloc(size, GFP_KERNEL);
> >>> +	if (!fence_info) {
> >>> +		ret = -ENOMEM;
> >>> +		goto out;
> >>> +	}
> >>>  
> >>>  	for (i = 0; i < sync_file->num_fences; ++i) {
> >>>  		struct fence *fence = sync_file->cbs[i].fence;
> >>>  
> >>> -		ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
> >>> +		ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
> >>> +					   size - len);
> >>>  
> >>>  		if (ret < 0)
> >>>  			goto out;
> >>> @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> >>>  		len += ret;
> >>>  	}
> >>>  
> >>> +	if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
> >>> +		ret = -EFAULT;
> >>> +		goto out;
> >>> +	}
> >>> +
> >>>  	info->len = len;
> >>> +	info->sync_fence_info = (__u64) in.sync_fence_info;
> >>> +
> >>> +no_fences:
> >>> +	info->num_fences = sync_file->num_fences;
> >>>  
> >>> -	if (copy_to_user((void __user *)arg, info, len))
> >>> +	if (copy_to_user((void __user *)arg, info, sizeof(*info)))
> >>>  		ret = -EFAULT;
> >>>  	else
> >>>  		ret = 0;
> >>>  
> >>>  out:
> >>> +	kfree(fence_info);
> >>>  	kfree(info);
> >>>  
> >>>  	return ret;
> >>> diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
> >>> index f0b41ce..9aad623 100644
> >>> --- a/drivers/staging/android/uapi/sync.h
> >>> +++ b/drivers/staging/android/uapi/sync.h
> >>> @@ -42,21 +42,20 @@ struct sync_fence_info {
> >>>  
> >>>  /**
> >>>   * struct sync_file_info - data returned from fence info ioctl
> >>> - * @len:	ioctl caller writes the size of the buffer its passing in.
> >>> - *		ioctl returns length of sync_file_info returned to
> >>> - *		userspace including pt_info.
> >>>   * @name:	name of fence
> >>>   * @status:	status of fence. 1: signaled 0:active <0:error
> >>>   * @num_fences	number of fences in the sync_file
> >>> + * @len:	ioctl caller writes the size of the buffer its passing in.
> >>> + *		ioctl returns length of all fence_infos summed.
> >>>   * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
> >>>   */
> >>>  struct sync_file_info {
> >>> -	__u32	len;
> >>>  	char	name[32];
> >>>  	__s32	status;
> >>>  	__u32	num_fences;
> >>> +	__u32	len;
> >>>  
> >>> -	__u8	sync_fence_info[0];
> >>> +	__u64	sync_fence_info;
> >>>  };
> >>>  
> >>>  #define SYNC_IOC_MAGIC		'>'
> >> Not sure if len adds anything here, userspace knows to allocate num_fences * sizeof(struct sync_fence_info);
> > I think of len being useful if we decide to extend struct sync_fence_info in
> > the future, so we may use len to help discover the size of each
> > sync_fence_info. What do you think?
> >
> I don't think you could extend it arbitrarily, you could make userspace pass a flag to indicate the struct is extended, so kernel space can choose
> whether to use the bigger size struct or not.
> 
> something like sync_file_info.flags = FENCE_INFO_V2; -- kernel can reject with -EINVAL if unsupported, or fill in a v2 struct.

Fair enough, I'll just remove len then.

	Gustavo