On Fri, Sep 22, 2023 at 10:28:56AM -0700, 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 tc_pedit.
> 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: Jamal Hadi Salim <j...@mojatatu.com>
> Cc: Cong Wang <xiyou.wangc...@gmail.com>
> Cc: Jiri Pirko <j...@resnulli.us>
> Cc: "David S. Miller" <da...@davemloft.net>
> Cc: Eric Dumazet <eduma...@google.com>
> Cc: Jakub Kicinski <k...@kernel.org>
> Cc: Paolo Abeni <pab...@redhat.com>
> Cc: net...@vger.kernel.org
> Signed-off-by: Kees Cook <keesc...@chromium.org>
> ---
> net/sched/act_pedit.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
> index 1ef8fcfa9997..77c407eff3b0 100644
> --- a/net/sched/act_pedit.c
> +++ b/net/sched/act_pedit.c
> @@ -515,11 +515,11 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct
> tc_action *a,
> spin_unlock_bh(&p->tcf_lock);
> return -ENOBUFS;
> }
> + opt->nkeys = parms->tcfp_nkeys;
>
> memcpy(opt->keys, parms->tcfp_keys,
> flex_array_size(opt, keys, parms->tcfp_nkeys));
> opt->index = p->tcf_index;
> - opt->nkeys = parms->tcfp_nkeys;
> opt->flags = parms->tcfp_flags;
> opt->action = p->tcf_action;
> opt->refcnt = refcount_read(&p->tcf_refcnt) - ref;
> --
> 2.34.1
>
Coccinelle was not happy about the #define ...
struct tc_pedit_sel {
tc_gen;
unsigned char nkeys;
unsigned char flags;
struct tc_pedit_key keys[0];
};
#define tc_pedit tc_pedit_sel
Also, it's not been converted to a proper flexible array...
--
Kees Cook
