Subject: [PATCH] netem: Annotate struct disttable with __counted_by

From: Kees Cook <[email-masked]>
Date: Tue, 3 Oct 2023 16:18:23 -0700

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 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 disttable.

Cc: Stephen Hemminger <[email-masked]>
Cc: Jamal Hadi Salim <[email-masked]>
Cc: Cong Wang <[email-masked]>
Cc: Jiri Pirko <[email-masked]>
Cc: "David S. Miller" <[email-masked]>
Cc: Eric Dumazet <[email-masked]>
Cc: Jakub Kicinski <[email-masked]>
Cc: Paolo Abeni <[email-masked]>
Cc: [email-masked]
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <[email-masked]>
---
 net/sched/sch_netem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 4ad39a4a3cf5..6ba2dc191ed9 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -67,7 +67,7 @@
 
 struct disttable {
 	u32  size;
-	s16 table[];
+	s16 table[] __counted_by(size);
 };
 
 struct netem_sched_data {
-- 
2.34.1