From 364bef150d9f2a03aebb427363031d56b244bf84 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marek=20Beh=C3=BAn?= Date: Thu, 20 May 2021 13:23:50 +0200 Subject: regmap: fix a serious pointer casting bug MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Simon Glass Cc: Heiko Schocher Cc: Bin Meng Cc: Pratyush Yadav --- drivers/core/regmap.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 57 insertions(+), 2 deletions(-) (limited to 'drivers/core') diff --git a/drivers/core/regmap.c b/drivers/core/regmap.c index b51ce108c1..3206f3d112 100644 --- a/drivers/core/regmap.c +++ b/drivers/core/regmap.c @@ -435,7 +435,36 @@ int regmap_raw_read(struct regmap *map, uint offset, void *valp, size_t val_len) int regmap_read(struct regmap *map, uint offset, uint *valp) { - return regmap_raw_read(map, offset, valp, map->width); + union { + u8 v8; + u16 v16; + u32 v32; + u64 v64; + } u; + int res; + + res = regmap_raw_read(map, offset, &u, map->width); + if (res) + return res; + + switch (map->width) { + case REGMAP_SIZE_8: + *valp = u.v8; + break; + case REGMAP_SIZE_16: + *valp = u.v16; + break; + case REGMAP_SIZE_32: + *valp = u.v32; + break; + case REGMAP_SIZE_64: + *valp = u.v64; + break; + default: + unreachable(); + } + + return 0; } static inline void __write_8(u8 *addr, const u8 *val, @@ -546,7 +575,33 @@ int regmap_raw_write(struct regmap *map, uint offset, const void *val, int regmap_write(struct regmap *map, uint offset, uint val) { - return regmap_raw_write(map, offset, &val, map->width); + union { + u8 v8; + u16 v16; + u32 v32; + u64 v64; + } u; + + switch (map->width) { + case REGMAP_SIZE_8: + u.v8 = val; + break; + case REGMAP_SIZE_16: + u.v16 = val; + break; + case REGMAP_SIZE_32: + u.v32 = val; + break; + case REGMAP_SIZE_64: + u.v64 = val; + break; + default: + debug("%s: regmap size %zu unknown\n", __func__, + (size_t)map->width); + return -EINVAL; + } + + return regmap_raw_write(map, offset, &u, map->width); } int regmap_update_bits(struct regmap *map, uint offset, uint mask, uint val) -- cgit v1.2.3