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 ceph_osd_request.

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

Cc: Ilya Dryomov <idryo...@gmail.com>
Cc: Xiubo Li <xiu...@redhat.com>
Cc: Jeff Layton <jlay...@kernel.org>
Cc: ceph-de...@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 include/linux/ceph/osd_client.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index bf9823956758..b8610e9d2471 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -278,7 +278,7 @@ struct ceph_osd_request {
        int r_attempts;
        u32 r_map_dne_bound;
 
-       struct ceph_osd_req_op r_ops[];
+       struct ceph_osd_req_op r_ops[] __counted_by(r_num_ops);
 };
 
 struct ceph_request_redirect {
-- 
2.34.1

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