linux-hardening - [PATCH] virtio_console: Annotate struct port_buffer with __counted

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Date: Fri, 22 Sep 2023 10:51:15 -0700
From: Kees Cook <keescook@...omium.org>
To: Amit Shah <amit@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	virtualization@...ts.linux-foundation.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] virtio_console: Annotate struct port_buffer 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 port_buffer.

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

Cc: Amit Shah <amit@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: virtualization@...ts.linux-foundation.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/char/virtio_console.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 680d1ef2a217..431e9e5bf9c1 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -106,7 +106,7 @@ struct port_buffer {
 	unsigned int sgpages;
 
 	/* sg is used if spages > 0. sg must be the last in is struct */
-	struct scatterlist sg[];
+	struct scatterlist sg[] __counted_by(sgpages);
 };
 
 /*
-- 
2.34.1