From patchwork Wed Jan 19 09:45:58 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: ext4: fix trim length underflow with small trim length. Date: Tue, 18 Jan 2011 23:45:58 -0000 From: Tao Ma X-Patchwork-Id: 79440 Message-Id: <1295430358-8912-1-git-send-email-tm@tao.ma> To: linux-ext4@vger.kernel.org Cc: Jan Kara From: Tao Ma In 0f0a25b, we adjust 'len' with s_first_data_block - start, but it could underflow in case blocksize=1K, while fstrim_range.len=512 and fstrim_range.start = 0. In this case len happens to be underflow and in the end, although we are safe that last_group check will limit the trim to the whole volume, I am afraid 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: Jan Kara Signed-off-by: Tao Ma --- fs/ext4/mballoc.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 851f49b..397db8d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4819,6 +4819,9 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb))) return -EINVAL; + if (start >= ext4_blocks_count(EXT4_SB(sb)->s_es) || + start + len <= first_data_blk) + goto out; if (start < first_data_blk) { len -= first_data_blk - start; start = first_data_blk; @@ -4863,5 +4866,6 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) } range->len = trimmed * sb->s_blocksize; +out: return ret; }