Re: [PATCH 14/14] net: sched: Annotate struct tc_pedit with __counted_by

[Gustavo A. R. Silva]

On 9/22/23 11:28, 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.

I think the annotation for struct tc_pedit_sel is missing.

Thanks
--
Gustavo

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;