Re: [PATCH] integrity: Annotate struct ima_rule_opt_list with __counted_by

[Jarkko Sakkinen]

On Fri Aug 18, 2023 at 12:03 AM EEST, 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@xxxxxxxxxxxxx>
> Cc: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
> Cc: Paul Moore <paul@xxxxxxxxxxxxxx>
> Cc: James Morris <jmorris@xxxxxxxxx>
> Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx>
> Cc: linux-integrity@xxxxxxxxxxxxxxx
> Cc: linux-security-module@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  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;
>  }
> -- 
> 2.34.1

Acked-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>

BR, Jarkko