netem: Annotate struct disttable with __counted_by

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: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Link: https://lore.kernel.org/r/20231003231823.work.684-kees@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 4ad39a4a3cf5bdec6a393deea0104f013149e26a..6ba2dc191ed941a3acfacb53cc4292388b076704 100644 (file)
--- 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 {