ext4: Fix mb_find_next_bit not to return larger than max
Some architectures implement ext4_find_next_bit and
ext4_find_next_zero_bit in such a way that they return
greater than max for some input values. Make sure
mb_find_next_bit and mb_find_next_zero_bit return the
right values.
On 2.6.25 we have include/asm-x86/bitops_32.h
static inline unsigned find_first_bit(const unsigned long *addr, unsigned size)
{
unsigned x = 0;
while (x < size) {
unsigned long val = *addr++;
if (val)
return __ffs(val) + x;
x += (sizeof(*addr)<<3);
}
return x;
}
This can return value greater than size.
Reported and fixed here for lustre
https://bugzilla.lustre.org/show_bug.cgi?id=15932
https://bugzilla.lustre.org/attachment.cgi?id=17205
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c9900aa..ba3aad2 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -381,22 +381,28 @@
static inline int mb_find_next_zero_bit(void *addr, int max, int start)
{
- int fix = 0;
+ int fix = 0, ret, tmpmax;
addr = mb_correct_addr_and_bit(&fix, addr);
- max += fix;
+ tmpmax = max + fix;
start += fix;
- return ext4_find_next_zero_bit(addr, max, start) - fix;
+ ret = ext4_find_next_zero_bit(addr, tmpmax, start) - fix;
+ if (ret > max)
+ return max;
+ return ret;
}
static inline int mb_find_next_bit(void *addr, int max, int start)
{
- int fix = 0;
+ int fix = 0, ret, tmpmax;
addr = mb_correct_addr_and_bit(&fix, addr);
- max += fix;
+ tmpmax = max + fix;
start += fix;
- return ext4_find_next_bit(addr, max, start) - fix;
+ ret = ext4_find_next_bit(addr, tmpmax, start) - fix;
+ if (ret > max)
+ return max;
+ return ret;
}
static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max)
@@ -3473,8 +3479,6 @@
if (bit >= end)
break;
next = mb_find_next_bit(bitmap_bh->b_data, end, bit);
- if (next > end)
- next = end;
start = group * EXT4_BLOCKS_PER_GROUP(sb) + bit +
le32_to_cpu(sbi->s_es->s_first_data_block);
mb_debug(" free preallocated %u/%u in group %u\n",