Commit 22f10457 authored Jul 10, 2011 by Tao Ma Committed by Theodore Ts'o Jul 10, 2011

ext4: fix trim length underflow with small trim length



In 0f0a25bf, 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>

parent 12706394

fs/ext4/mballoc.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

Admin message