[PATCH] selinux: Annotate struct sidtab_str_cache with __counted_by

[PATCH] selinux: Annotate struct sidtab_str_cache with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct sidtab_str_cache.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Cc: selinux@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 security/selinux/ss/sidtab.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
index d8ead463b8df..732fd8e22a12 100644
--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -25,7 +25,7 @@ struct sidtab_str_cache {
 	struct list_head lru_member;
 	struct sidtab_entry *parent;
 	u32 len;
-	char str[];
+	char str[] __counted_by(len);
 };
 
 #define index_to_sid(index) ((index) + SECINITSID_NUM + 1)
-- 
2.34.1

Re: [PATCH] selinux: Annotate struct sidtab_str_cache with __counted_by

[Gustavo A. R. Silva]

On 8/17/23 14:22, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct sidtab_str_cache.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> Cc: Eric Paris <eparis@parisplace.org>
> Cc: Ondrej Mosnacek <omosnace@redhat.com>
> Cc: selinux@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
>   security/selinux/ss/sidtab.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
> index d8ead463b8df..732fd8e22a12 100644
> --- a/security/selinux/ss/sidtab.c
> +++ b/security/selinux/ss/sidtab.c
> @@ -25,7 +25,7 @@ struct sidtab_str_cache {
>   	struct list_head lru_member;
>   	struct sidtab_entry *parent;
>   	u32 len;
> -	char str[];
> +	char str[] __counted_by(len);
>   };
>   
>   #define index_to_sid(index) ((index) + SECINITSID_NUM + 1)

Re: [PATCH] selinux: Annotate struct sidtab_str_cache with __counted_by

[Paul Moore]

On Thu, Aug 17, 2023 at 4:22 PM Kees Cook <keescook@chromium.org> wrote:
>
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct sidtab_str_cache.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> Cc: Eric Paris <eparis@parisplace.org>
> Cc: Ondrej Mosnacek <omosnace@redhat.com>
> Cc: selinux@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  security/selinux/ss/sidtab.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

This also looks good to me, but similarly to the audit patch, since we
are at -rc6 I'm going to wait to merge this until after the merge
window.  I'll send a follow up email once it's merged.

Thanks.

> diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
> index d8ead463b8df..732fd8e22a12 100644
> --- a/security/selinux/ss/sidtab.c
> +++ b/security/selinux/ss/sidtab.c
> @@ -25,7 +25,7 @@ struct sidtab_str_cache {
>         struct list_head lru_member;
>         struct sidtab_entry *parent;
>         u32 len;
> -       char str[];
> +       char str[] __counted_by(len);
>  };
>
>  #define index_to_sid(index) ((index) + SECINITSID_NUM + 1)
> --
> 2.34.1

-- 
paul-moore.com

Re: [PATCH] selinux: Annotate struct sidtab_str_cache with __counted_by

[Kees Cook]

On Fri, Aug 18, 2023 at 12:25:12PM -0400, Paul Moore wrote:
> On Thu, Aug 17, 2023 at 4:22 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > Prepare for the coming implementation by GCC and Clang of the __counted_by
> > attribute. Flexible array members annotated with __counted_by can have
> > their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> > (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> > functions).
> >
> > As found with Coccinelle[1], add __counted_by for struct sidtab_str_cache.
> >
> > [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> >
> > Cc: Paul Moore <paul@paul-moore.com>
> > Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> > Cc: Eric Paris <eparis@parisplace.org>
> > Cc: Ondrej Mosnacek <omosnace@redhat.com>
> > Cc: selinux@vger.kernel.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  security/selinux/ss/sidtab.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> This also looks good to me, but similarly to the audit patch, since we
> are at -rc6 I'm going to wait to merge this until after the merge
> window.  I'll send a follow up email once it's merged.

Thanks! Yeah, there's no rush. :)

-- 
Kees Cook

Re: [PATCH] selinux: Annotate struct sidtab_str_cache with __counted_by

[Paul Moore]

On Aug 17, 2023 Kees Cook <keescook@chromium.org> wrote:
> 
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct sidtab_str_cache.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> Cc: Eric Paris <eparis@parisplace.org>
> Cc: Ondrej Mosnacek <omosnace@redhat.com>
> Cc: selinux@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  security/selinux/ss/sidtab.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Merged into selinux/next, thanks.

--
paul-moore.com