linux-hardening - Re: [PATCH] integrity: Annotate struct ima_rule_opt_list with __counted

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Date:   Thu, 17 Aug 2023 15:20:49 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>, Mimi Zohar <zohar@...ux.ibm.com>
Cc:     Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] integrity: Annotate struct ima_rule_opt_list with
 __counted_by



On 8/17/23 15:03, 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 ima_rule_opt_list.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Mimi Zohar <zohar@...ux.ibm.com>
> Cc: Dmitry Kasatkin <dmitry.kasatkin@...il.com>
> Cc: Paul Moore <paul@...l-moore.com>
> Cc: James Morris <jmorris@...ei.org>
> Cc: "Serge E. Hallyn" <serge@...lyn.com>
> Cc: linux-integrity@...r.kernel.org
> Cc: linux-security-module@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

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

Thanks
--
Gustavo

> ---
>   security/integrity/ima/ima_policy.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 69452b79686b..f69062617754 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -68,7 +68,7 @@ enum policy_rule_list { IMA_DEFAULT_POLICY = 1, IMA_CUSTOM_POLICY };
>   
>   struct ima_rule_opt_list {
>   	size_t count;
> -	char *items[];
> +	char *items[] __counted_by(count);
>   };
>   
>   /*
> @@ -342,6 +342,7 @@ static struct ima_rule_opt_list *ima_alloc_rule_opt_list(const substring_t *src)
>   		kfree(src_copy);
>   		return ERR_PTR(-ENOMEM);
>   	}
> +	opt_list->count = count;
>   
>   	/*
>   	 * strsep() has already replaced all instances of '|' with '\0',
> @@ -357,7 +358,6 @@ static struct ima_rule_opt_list *ima_alloc_rule_opt_list(const substring_t *src)
>   		opt_list->items[i] = cur;
>   		cur = strchr(cur, '\0') + 1;
>   	}
> -	opt_list->count = count;
>   
>   	return opt_list;
>   }