On 9/15/23 14:04, 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 dm_bio_prison.

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

Cc: Alasdair Kergon <a...@redhat.com>
Cc: Mike Snitzer <snit...@kernel.org>
Cc: dm-devel@redhat.com
Signed-off-by: Kees Cook <keesc...@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavo...@kernel.org>

Thanks
--
Gustavo

---
  drivers/md/dm-bio-prison-v1.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-bio-prison-v1.c b/drivers/md/dm-bio-prison-v1.c
index 92afdca760ae..9ab32abe5ed4 100644
--- a/drivers/md/dm-bio-prison-v1.c
+++ b/drivers/md/dm-bio-prison-v1.c
@@ -26,7 +26,7 @@ struct prison_region {
  struct dm_bio_prison {
        mempool_t cell_pool;
        unsigned int num_locks;
-       struct prison_region regions[];
+       struct prison_region regions[] __counted_by(num_locks);
  };
static struct kmem_cache *_cell_cache;

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