io_uring/rsrc: Annotate struct io_mapped_ubuf 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 io_mapped_ubuf.

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

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: io-uring@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230817212146.never.853-kees@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 8afa9ec..8625181 100644 (file)
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -54,7 +54,7 @@ struct io_mapped_ubuf {
        u64             ubuf_end;
        unsigned int    nr_bvecs;
        unsigned long   acct_pages;
-       struct bio_vec  bvec[];
+       struct bio_vec  bvec[] __counted_by(nr_bvecs);
 };
 
 void io_rsrc_node_ref_zero(struct io_rsrc_node *node);