From: Tao Ma Date: Mon, 11 Jul 2011 03:52:37 +0000 (-0400) Subject: ext4: fix trim length underflow with small trim length X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=22f10457432387615fa1ae6e0375d9cacc50819b;p=linux-edison.git 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 Signed-off-by: Tao Ma Signed-off-by: "Theodore Ts'o" --- diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 1900ec7a157..b189cb4ff20 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -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; }