watch_queue: Annotate struct watch_filter 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 watch_filter.

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

Cc: David Howells <dhowells@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Siddh Raman Pant <code@siddh.me>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Qian Cai <cai@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Siddh Raman Pant <code@siddh.me>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Message-Id: <20230922175407.work.754-kees@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
index 45cd42f55d49298922886bff572d4480f84c396a..429c7b6afeada77dc624e139a2a93fe7e47fbde8 100644 (file)
--- a/include/linux/watch_queue.h
+++ b/include/linux/watch_queue.h
@@ -32,7 +32,7 @@ struct watch_filter {
                DECLARE_BITMAP(type_filter, WATCH_TYPE__NR);
        };
        u32                     nr_filters;     /* Number of filters */
-       struct watch_type_filter filters[];
+       struct watch_type_filter filters[] __counted_by(nr_filters);
 };
 
 struct watch_queue {