linux-hardening - [PATCH] mtd: cfi: Annotate struct cfi_private with __counted

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Message-Id: <20230915201206.never.107-kees@kernel.org>
Date:   Fri, 15 Sep 2023 13:12:06 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.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] mtd: cfi: Annotate struct cfi_private 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 cfi_private.

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

Cc: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Richard Weinberger <richard@....at>
Cc: Vignesh Raghavendra <vigneshr@...com>
Cc: linux-mtd@...ts.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/mtd/cfi.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mtd/cfi.h b/include/linux/mtd/cfi.h
index d88bb56c18e2..947410faf9e2 100644
--- a/include/linux/mtd/cfi.h
+++ b/include/linux/mtd/cfi.h
@@ -287,7 +287,7 @@ struct cfi_private {
 	unsigned long chipshift; /* Because they're of the same type */
 	const char *im_name;	 /* inter_module name for cmdset_setup */
 	unsigned long quirks;
-	struct flchip chips[];  /* per-chip data structure for each chip */
+	struct flchip chips[] __counted_by(numchips);  /* per-chip data structure for each chip */
 };
 
 uint32_t cfi_build_cmd_addr(uint32_t cmd_ofs,
-- 
2.34.1