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regmap: fix a serious pointer casting bug

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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@nic.cz>
Cc: Simon Glass <sjg@chromium.org>
Cc: Heiko Schocher <hs@denx.de>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Pratyush Yadav <p.yadav@ti.com>
This commit is contained in:
Marek Behún 2021-05-20 13:23:50 +02:00 committed by Tom Rini
parent 2177f924bf
commit 364bef150d
1 changed files with 57 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
drivers/core/regmap.c
View File

@ -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)