linux-hardening - [PATCH] aio: Annotate struct kioctx_table with __counted

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Message-Id: <20230915201413.never.881-kees@kernel.org>
Date:   Fri, 15 Sep 2023 13:14:14 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Benjamin LaHaise <bcrl@...ck.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, linux-aio@...ck.org,
        linux-fsdevel@...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] aio: Annotate struct kioctx_table 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 kioctx_table.

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

Cc: Benjamin LaHaise <bcrl@...ck.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Christian Brauner <brauner@...nel.org>
Cc: linux-aio@...ck.org
Cc: linux-fsdevel@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/aio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/aio.c b/fs/aio.c
index a4c2a6bac72c..f8589caef9c1 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -80,7 +80,7 @@ struct aio_ring {
 struct kioctx_table {
 	struct rcu_head		rcu;
 	unsigned		nr;
-	struct kioctx __rcu	*table[];
+	struct kioctx __rcu	*table[] __counted_by(nr);
 };
 
 struct kioctx_cpu {
-- 
2.34.1