linux-hardening - [PATCH] io_uring/rsrc: Annotate struct io_mapped_ubuf with __counted

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Date:   Thu, 17 Aug 2023 14:21:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Kees Cook <keescook@...omium.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        io-uring@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: [PATCH] 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@...nel.dk>
Cc: Pavel Begunkov <asml.silence@...il.com>
Cc: io-uring@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 io_uring/rsrc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 8afa9ec66a55..8625181fb87a 100644
--- 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);
-- 
2.34.1