dm: Annotate struct dm_stat 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 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 dm_stat.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: dm-devel@redhat.com
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230915200400.never.585-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index db2d997a6c1815ce6f7f72fa0fed51572afae856..bdc14ec9981414c60e1dee432b97d50e82dbbc88 100644 (file)
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -56,7 +56,7 @@ struct dm_stat {
        size_t percpu_alloc_size;
        size_t histogram_alloc_size;
        struct dm_stat_percpu *stat_percpu[NR_CPUS];
-       struct dm_stat_shared stat_shared[];
+       struct dm_stat_shared stat_shared[] __counted_by(n_entries);
 };
 
 #define STAT_PRECISE_TIMESTAMPS                1