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ext4: fix trim length underflow with small trim length 

In 0f0a25b, we adjust 'len' with s_first_data_block - start, but
it could underflow in case blocksize=1K, fstrim_range.len=512 and
fstrim_range.start = 0. In this case, when we run the code:
len -= first_data_blk - start; len will be underflow to -1ULL.
In the end, although we are safe that last_group check later will limit
the trim to the whole volume, but that isn't what the user really want.

So this patch fix it. It also adds the check for 'start' like ext3 so that
we can break immediately if the start is invalid.

Cc: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Tao Ma 2011-07-10 23:52:37 -04:00 committed by Theodore Ts'o
parent 12706394bc
commit 22f1045743
1 changed files with 3 additions and 0 deletions
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3
fs/ext4/mballoc.c
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@ -4902,6 +4902,8 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
return -EINVAL;
if (start + len <= first_data_blk)
goto out;
if (start < first_data_blk) {
len -= first_data_blk - start;
start = first_data_blk;
@ -4950,5 +4952,6 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
}
range->len = trimmed * sb->s_blocksize;
out:
return ret;
}