From: Dan Carpenter dan.carpenter@oracle.com
commit 3e3765875b1b8864898603768fd5c93eeb552211 upstream.
The problem is that "erasesize" is a uint64_t type so it might be non-zero but the lower 32 bits are zero so when it's truncated, "(uint32_t)erasesize", then that value is zero. This leads to a divide by zero bug.
Avoid the bug by delaying the divide until after we have validated that "erasesize" is non-zero and within the uint32_t range.
Fixes: dc2b3e5cbc80 ("mtd: phram: use div_u64_rem to stop overwrite len in phram_setup") Signed-off-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Miquel Raynal miquel.raynal@bootlin.com Link: https://lore.kernel.org/linux-mtd/20220121115505.GI1978@kadam Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/mtd/devices/phram.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/drivers/mtd/devices/phram.c +++ b/drivers/mtd/devices/phram.c @@ -264,15 +264,19 @@ static int phram_setup(const char *val) } }
- if (erasesize) - div_u64_rem(len, (uint32_t)erasesize, &rem); - if (len == 0 || erasesize == 0 || erasesize > len - || erasesize > UINT_MAX || rem) { + || erasesize > UINT_MAX) { parse_err("illegal erasesize or len\n"); ret = -EINVAL; goto error; } + + div_u64_rem(len, (uint32_t)erasesize, &rem); + if (rem) { + parse_err("len is not multiple of erasesize\n"); + ret = -EINVAL; + goto error; + }
ret = register_device(name, start, len, (uint32_t)erasesize); if (ret)