diff mbox series

vboxsf: Use flexible arrays for trailing string member

Message ID 20230720151458.never.673-kees@kernel.org
State New
Headers
Series vboxsf: Use flexible arrays for trailing string member |

Commit Message

Kees Cook July 20, 2023, 3:15 p.m. UTC 
  The declaration of struct shfl_string used trailing fake flexible arrays
for the string member. This was tripping FORTIFY_SOURCE since commit
df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3"). Replace the
utf8 and utf16 members with actual flexible arrays, drop the unused ucs2
member, and retriain a 2 byte padding to keep the structure size the same.

Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Closes: https://lore.kernel.org/lkml/ab3a70e9-60ed-0f13-e3d4-8866eaccc8c1@lwfinger.net/
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/vboxsf/shfl_hostintf.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Hans de Goede July 25, 2023, 9 a.m. UTC | #1 
Hi Kees, Larry,

On 7/20/23 17:15, Kees Cook wrote:
> The declaration of struct shfl_string used trailing fake flexible arrays
> for the string member. This was tripping FORTIFY_SOURCE since commit
> df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3"). Replace the
> utf8 and utf16 members with actual flexible arrays, drop the unused ucs2
> member, and retriain a 2 byte padding to keep the structure size the same.
> 
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Closes: https://lore.kernel.org/lkml/ab3a70e9-60ed-0f13-e3d4-8866eaccc8c1@lwfinger.net/
> Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Kees, Larry thank you for fixing this while I was on vacation.

The patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Kees, I'm the vboxsf maintainer and it would be easiest for
me if you can include this in a future 6.5 fixes pull-request
to Linus if that is possible ?

Regards,

Hans



> ---
>  fs/vboxsf/shfl_hostintf.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/vboxsf/shfl_hostintf.h b/fs/vboxsf/shfl_hostintf.h
> index aca829062c12..069a019c9247 100644
> --- a/fs/vboxsf/shfl_hostintf.h
> +++ b/fs/vboxsf/shfl_hostintf.h
> @@ -68,9 +68,9 @@ struct shfl_string {
>  
>  	/** UTF-8 or UTF-16 string. Nul terminated. */
>  	union {
> -		u8 utf8[2];
> -		u16 utf16[1];
> -		u16 ucs2[1]; /* misnomer, use utf16. */
> +		u8 legacy_padding[2];
> +		DECLARE_FLEX_ARRAY(u8, utf8);
> +		DECLARE_FLEX_ARRAY(u16, utf16);
>  	} string;
>  };
>  VMMDEV_ASSERT_SIZE(shfl_string, 6);
Kees Cook July 26, 2023, 9:55 p.m. UTC | #2 
On Thu, 20 Jul 2023 08:15:06 -0700, Kees Cook wrote:
> The declaration of struct shfl_string used trailing fake flexible arrays
> for the string member. This was tripping FORTIFY_SOURCE since commit
> df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3"). Replace the
> utf8 and utf16 members with actual flexible arrays, drop the unused ucs2
> member, and retriain a 2 byte padding to keep the structure size the same.
> 
> 
> [...]

Applied to for-linus/hardening, thanks!

[1/1] vboxsf: Use flexible arrays for trailing string member
      https://git.kernel.org/kees/c/a8f014ec6a21

Best regards,
Larry Finger Aug. 8, 2023, 7:20 p.m. UTC | #3 
On 7/26/23 16:55, Kees Cook wrote:
> 
> On Thu, 20 Jul 2023 08:15:06 -0700, Kees Cook wrote:
>> The declaration of struct shfl_string used trailing fake flexible arrays
>> for the string member. This was tripping FORTIFY_SOURCE since commit
>> df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3"). Replace the
>> utf8 and utf16 members with actual flexible arrays, drop the unused ucs2
>> member, and retriain a 2 byte padding to keep the structure size the same.
>>
>>
>> [...]
> 
> Applied to for-linus/hardening, thanks!
> 
> [1/1] vboxsf: Use flexible arrays for trailing string member
>        https://git.kernel.org/kees/c/a8f014ec6a21

Kees,

This patch has not been applied to kernel 6.5-rc5. Is there some problem?

Larry
Kees Cook Aug. 8, 2023, 9:01 p.m. UTC | #4 
On Tue, Aug 08, 2023 at 02:20:06PM -0500, Larry Finger wrote:
> On 7/26/23 16:55, Kees Cook wrote:
> > 
> > On Thu, 20 Jul 2023 08:15:06 -0700, Kees Cook wrote:
> > > The declaration of struct shfl_string used trailing fake flexible arrays
> > > for the string member. This was tripping FORTIFY_SOURCE since commit
> > > df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3"). Replace the
> > > utf8 and utf16 members with actual flexible arrays, drop the unused ucs2
> > > member, and retriain a 2 byte padding to keep the structure size the same.
> > > 
> > > 
> > > [...]
> > 
> > Applied to for-linus/hardening, thanks!
> > 
> > [1/1] vboxsf: Use flexible arrays for trailing string member
> >        https://git.kernel.org/kees/c/a8f014ec6a21
> 
> Kees,
> 
> This patch has not been applied to kernel 6.5-rc5. Is there some problem?

Hi! Sorry, I was waiting for linux-next testing, and then got distracted
on Friday. I will send the PR to Linus today.

Thanks for the poke!

-Kees
diff mbox series

Patch

diff --git a/fs/vboxsf/shfl_hostintf.h b/fs/vboxsf/shfl_hostintf.h
index aca829062c12..069a019c9247 100644
--- a/fs/vboxsf/shfl_hostintf.h
+++ b/fs/vboxsf/shfl_hostintf.h
@@ -68,9 +68,9 @@  struct shfl_string {
 
 	/** UTF-8 or UTF-16 string. Nul terminated. */
 	union {
-		u8 utf8[2];
-		u16 utf16[1];
-		u16 ucs2[1]; /* misnomer, use utf16. */
+		u8 legacy_padding[2];
+		DECLARE_FLEX_ARRAY(u8, utf8);
+		DECLARE_FLEX_ARRAY(u16, utf16);
 	} string;
 };
 VMMDEV_ASSERT_SIZE(shfl_string, 6);