[PATCH u-boot v4 01/36] regmap: fix a serious pointer casting bug

Tom Rini trini at konsulko.com
Tue May 25 02:54:12 CEST 2021

On Thu, May 20, 2021 at 01:23:50PM +0200, Marek Behún wrote:

> There is a serious bug in regmap_read() and regmap_write() functions
> where an uint pointer is cast to (void *) which is then cast to (u8 *),
> (u16 *), (u32 *) or (u64 *), depending on register width of the map.
> For example given a regmap with 16-bit register width the code
> 	int val = 0x12340000;
> 	regmap_read(map, 0, &val);
> only changes the lower 16 bits of val on little-endian machines.
> The upper 16 bits will remain 0x1234.
> Nobody noticed this probably because this bug can be triggered with
> regmap_write() only on big-endian architectures (which are not used by
> many people anymore), and on little endian this bug has consequences
> only if register width is 8 or 16 bits and also the memory place to
> which regmap_read() should store it's result has non-zero upper bits,
> which it seems doesn't happen anywhere in U-Boot normally. CI managed to
> trigger this bug in unit test of dm_test_devm_regmap_field when compiled
> for sandbox_defconfig using LTO.
> Fix this by utilizing an union { u8; u16; u32; u64; } and reading data
> into this union / writing data from this union.
> Signed-off-by: Marek Behún <marek.behun at nic.cz>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Heiko Schocher <hs at denx.de>
> Cc: Bin Meng <bmeng.cn at gmail.com>
> Cc: Pratyush Yadav <p.yadav at ti.com>

Applied to u-boot/master, thanks!

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