linux-kernel - Re: [PATCH] selinux: Annotate struct sidtab_str_cache with __counted

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Message-ID: <ae4756a2-55a4-fe0b-50e0-b87c17151354@embeddedor.com>
Date:   Thu, 17 Aug 2023 14:53:07 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>, Paul Moore <paul@...l-moore.com>
Cc:     Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>, selinux@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        "GONG, Ruiqi" <gongruiqi1@...wei.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] selinux: Annotate struct sidtab_str_cache with
 __counted_by



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@...l-moore.com>
> Cc: Stephen Smalley <stephen.smalley.work@...il.com>
> Cc: Eric Paris <eparis@...isplace.org>
> Cc: Ondrej Mosnacek <omosnace@...hat.com>
> Cc: selinux@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.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)