[v18,07/15] fs/namespace: untag user pointers in copy_mount_options

Submitted by Andrey Konovalov on June 24, 2019, 2:32 p.m.

Details

Message ID 41e0a911e4e4d533486a1468114e6878e21f9f84.1561386715.git.andreyknvl@google.com
State New
Headers show
Series "arm64: untag user pointers passed to the kernel" ( rev: 8 ) in AMD X.Org drivers

Not browsing as part of any series.

Commit Message

Andrey Konovalov June 24, 2019, 2:32 p.m.
This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.

In copy_mount_options a user address is being subtracted from TASK_SIZE.
If the address is lower than TASK_SIZE, the size is calculated to not
allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
However if the address is tagged, then the size will be calculated
incorrectly.

Untag the address before subtracting.

Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 fs/namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch hide | download patch | download mbox

diff --git a/fs/namespace.c b/fs/namespace.c
index 7660c2749c96..ec78f7223917 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2994,7 +2994,7 @@  void *copy_mount_options(const void __user * data)
 	 * the remainder of the page.
 	 */
 	/* copy_from_user cannot cross TASK_SIZE ! */
-	size = TASK_SIZE - (unsigned long)data;
+	size = TASK_SIZE - (unsigned long)untagged_addr(data);
 	if (size > PAGE_SIZE)
 		size = PAGE_SIZE;
 

Comments

On Mon, Jun 24, 2019 at 04:32:52PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends kernel ABI to allow to pass
> tagged user pointers (with the top byte set to something else other than
> 0x00) as syscall arguments.
> 
> In copy_mount_options a user address is being subtracted from TASK_SIZE.
> If the address is lower than TASK_SIZE, the size is calculated to not
> allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
> However if the address is tagged, then the size will be calculated
> incorrectly.
> 
> Untag the address before subtracting.
> 
> Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  fs/namespace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 7660c2749c96..ec78f7223917 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2994,7 +2994,7 @@ void *copy_mount_options(const void __user * data)
>  	 * the remainder of the page.
>  	 */
>  	/* copy_from_user cannot cross TASK_SIZE ! */
> -	size = TASK_SIZE - (unsigned long)data;
> +	size = TASK_SIZE - (unsigned long)untagged_addr(data);
>  	if (size > PAGE_SIZE)
>  		size = PAGE_SIZE;

I think this patch needs an ack from Al Viro (cc'ed).
On Mon, Jun 24, 2019 at 7:50 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> On Mon, Jun 24, 2019 at 04:32:52PM +0200, Andrey Konovalov wrote:
> > This patch is a part of a series that extends kernel ABI to allow to pass
> > tagged user pointers (with the top byte set to something else other than
> > 0x00) as syscall arguments.
> >
> > In copy_mount_options a user address is being subtracted from TASK_SIZE.
> > If the address is lower than TASK_SIZE, the size is calculated to not
> > allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
> > However if the address is tagged, then the size will be calculated
> > incorrectly.
> >
> > Untag the address before subtracting.
> >
> > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
> > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > ---
> >  fs/namespace.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/namespace.c b/fs/namespace.c
> > index 7660c2749c96..ec78f7223917 100644
> > --- a/fs/namespace.c
> > +++ b/fs/namespace.c
> > @@ -2994,7 +2994,7 @@ void *copy_mount_options(const void __user * data)
> >        * the remainder of the page.
> >        */
> >       /* copy_from_user cannot cross TASK_SIZE ! */
> > -     size = TASK_SIZE - (unsigned long)data;
> > +     size = TASK_SIZE - (unsigned long)untagged_addr(data);
> >       if (size > PAGE_SIZE)
> >               size = PAGE_SIZE;
>
> I think this patch needs an ack from Al Viro (cc'ed).
>
> --
> Catalin

Hi Al,

Could you take a look and give your acked-by?

Thanks!
+Eric Biederman too, who might be able to Ack this...

On Mon, Jul 15, 2019 at 06:00:04PM +0200, Andrey Konovalov wrote:
> On Mon, Jun 24, 2019 at 7:50 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
> >
> > On Mon, Jun 24, 2019 at 04:32:52PM +0200, Andrey Konovalov wrote:
> > > This patch is a part of a series that extends kernel ABI to allow to pass
> > > tagged user pointers (with the top byte set to something else other than
> > > 0x00) as syscall arguments.
> > >
> > > In copy_mount_options a user address is being subtracted from TASK_SIZE.
> > > If the address is lower than TASK_SIZE, the size is calculated to not
> > > allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
> > > However if the address is tagged, then the size will be calculated
> > > incorrectly.
> > >
> > > Untag the address before subtracting.
> > >
> > > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
> > > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> > > Reviewed-by: Kees Cook <keescook@chromium.org>
> > > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > > ---
> > >  fs/namespace.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/namespace.c b/fs/namespace.c
> > > index 7660c2749c96..ec78f7223917 100644
> > > --- a/fs/namespace.c
> > > +++ b/fs/namespace.c
> > > @@ -2994,7 +2994,7 @@ void *copy_mount_options(const void __user * data)
> > >        * the remainder of the page.
> > >        */
> > >       /* copy_from_user cannot cross TASK_SIZE ! */
> > > -     size = TASK_SIZE - (unsigned long)data;
> > > +     size = TASK_SIZE - (unsigned long)untagged_addr(data);
> > >       if (size > PAGE_SIZE)
> > >               size = PAGE_SIZE;
> >
> > I think this patch needs an ack from Al Viro (cc'ed).
> >
> > --
> > Catalin
> 
> Hi Al,
> 
> Could you take a look and give your acked-by?
> 
> Thanks!