find_next_zero_bit() incorrectly handles cases when: - total bitmap size < 32 - rest of bits to process

static inline int find_next_zero_bit(void *addr, int size, int offset) { unsigned long *p = ((unsigned long *)addr) + (offset >> 5); unsigned long result = offset & ~31UL; unsigned long tmp;

if (offset >= size) return size; size -= result; offset &= 31UL; if (offset) { tmp = *(p++); tmp |= ~0UL >> (32-offset); if (size < 32) [1] goto found_first; if (~tmp) goto found_middle; size -= 32; result += 32; } while (size & ~31UL) { tmp = *(p++); if (~tmp) goto found_middle; result += 32; size -= 32; } [2] if (!size) return result; tmp = *p;

found_first: [3] tmp |= ~0UL >> size;

^^^ algo can reach above line from from points: [1] offset > 0 and size < 32, tmp[offset-1..0] bits set to 1 [2] size < 32 - rest of bits to process in both cases bits to search are tmp[size-1..0], but line [3] will simply set all tmp[31-size..0] bits to 1 and ffz(tmp) below will fail.

example: bitmap size = 16, offset = 0, bitmap is empty. code will go through the point [2], tmp = 0x0 after line [3] => tmp = 0xFFFF and ffz(tmp) will return 16.

found_middle: return result + ffz(tmp); }

Fix it by correctly seting tmp[31..size] bits to 1 in the above case [3].

Fixes: 81e9fe5a2988 ("arm: implement find_next_zero_bit function") Signed-off-by: Grygorii Strashko grygorii.strashko@ti.com --- arch/arm/include/asm/bitops.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/bitops.h b/arch/arm/include/asm/bitops.h index f33efeb..2750d9b 100644 --- a/arch/arm/include/asm/bitops.h +++ b/arch/arm/include/asm/bitops.h @@ -158,7 +158,7 @@ static inline int find_next_zero_bit(void *addr, int size, int offset) tmp = *p;

found_first: - tmp |= ~0UL >> size; + tmp |= ~0UL << size; found_middle: return result + ffz(tmp); }