[v16,08/16] fs, arm64: untag user pointers in copy_mount_options
diff mbox series

Message ID 51f44a12c4e81c9edea8dcd268f820f5d1fad87c.1559580831.git.andreyknvl@google.com
State New
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Series
  • arm64: untag user pointers passed to the kernel
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Commit Message

Andrey Konovalov June 3, 2019, 4:55 p.m. UTC
This patch is a part of a series that extends arm64 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: 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(-)

Comments

Kees Cook June 8, 2019, 4:02 a.m. UTC | #1
On Mon, Jun 03, 2019 at 06:55:10PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 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: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

One thing I just noticed in the commit titles... "arm64" is in the
prefix, but these are arch-indep areas. Should the ", arm64" be left
out?

I would expect, instead:

	fs/namespace: untag user pointers in copy_mount_options

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  fs/namespace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index b26778bdc236..2e85712a19ed 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2993,7 +2993,7 @@ 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;
>  
> -- 
> 2.22.0.rc1.311.g5d7573a151-goog
>
Andrey Konovalov June 11, 2019, 2:38 p.m. UTC | #2
On Sat, Jun 8, 2019 at 6:02 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Jun 03, 2019 at 06:55:10PM +0200, Andrey Konovalov wrote:
> > This patch is a part of a series that extends arm64 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: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>
> One thing I just noticed in the commit titles... "arm64" is in the
> prefix, but these are arch-indep areas. Should the ", arm64" be left
> out?
>
> I would expect, instead:
>
>         fs/namespace: untag user pointers in copy_mount_options

Hm, I've added the arm64 tag in all of the patches because they are
related to changes in arm64 kernel ABI. I can remove it from all the
patches that only touch common code if you think that it makes sense.

Thanks!

>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
> -Kees
>
> > ---
> >  fs/namespace.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/namespace.c b/fs/namespace.c
> > index b26778bdc236..2e85712a19ed 100644
> > --- a/fs/namespace.c
> > +++ b/fs/namespace.c
> > @@ -2993,7 +2993,7 @@ 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;
> >
> > --
> > 2.22.0.rc1.311.g5d7573a151-goog
> >
>
> --
> Kees Cook
Andrey Konovalov June 12, 2019, 11:36 a.m. UTC | #3
On Tue, Jun 11, 2019 at 4:38 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> On Sat, Jun 8, 2019 at 6:02 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Mon, Jun 03, 2019 at 06:55:10PM +0200, Andrey Konovalov wrote:
> > > This patch is a part of a series that extends arm64 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: Catalin Marinas <catalin.marinas@arm.com>
> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >
> > One thing I just noticed in the commit titles... "arm64" is in the
> > prefix, but these are arch-indep areas. Should the ", arm64" be left
> > out?
> >
> > I would expect, instead:
> >
> >         fs/namespace: untag user pointers in copy_mount_options
>
> Hm, I've added the arm64 tag in all of the patches because they are
> related to changes in arm64 kernel ABI. I can remove it from all the
> patches that only touch common code if you think that it makes sense.

I'll keep the arm64 tags in commit titles for v17. Please reply
explicitly if you think I should remove them. Thanks! :)

>
> Thanks!
>
> >
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> >
> > -Kees
> >
> > > ---
> > >  fs/namespace.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/namespace.c b/fs/namespace.c
> > > index b26778bdc236..2e85712a19ed 100644
> > > --- a/fs/namespace.c
> > > +++ b/fs/namespace.c
> > > @@ -2993,7 +2993,7 @@ 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;
> > >
> > > --
> > > 2.22.0.rc1.311.g5d7573a151-goog
> > >
> >
> > --
> > Kees Cook

Patch
diff mbox series

diff --git a/fs/namespace.c b/fs/namespace.c
index b26778bdc236..2e85712a19ed 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2993,7 +2993,7 @@  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;