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 sunxi_nand_chip.

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

Cc: Miquel Raynal <miquel.ray...@bootlin.com>
Cc: Richard Weinberger <rich...@nod.at>
Cc: Vignesh Raghavendra <vigne...@ti.com>
Cc: Chen-Yu Tsai <w...@csie.org>
Cc: Jernej Skrabec <jernej.skra...@gmail.com>
Cc: Samuel Holland <sam...@sholland.org>
Cc: Manuel Dipolt <mdip...@robart.cc>
Cc: linux-...@lists.infradead.org
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-su...@lists.linux.dev
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 drivers/mtd/nand/raw/sunxi_nand.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/sunxi_nand.c 
b/drivers/mtd/nand/raw/sunxi_nand.c
index 9abf38049d35..4ec17c8bce5a 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -197,7 +197,7 @@ struct sunxi_nand_chip {
        u32 timing_cfg;
        u32 timing_ctl;
        int nsels;
-       struct sunxi_nand_chip_sel sels[];
+       struct sunxi_nand_chip_sel sels[] __counted_by(nsels);
 };
 
 static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
-- 
2.34.1

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