Patchwork [1/5] ext4: fix trim length underflow with small trim length.

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Submitter Tao Ma
Date July 1, 2011, 3:27 p.m.
Message ID <1309534076-2784-1-git-send-email-tm@tao.ma>
Download mbox | patch
Permalink /patch/102915/
State Accepted
Headers show

Comments

Tao Ma - July 1, 2011, 3:27 p.m.
From: Tao Ma <boyu.mt@taobao.com>

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>
---
 fs/ext4/mballoc.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
Theodore Ts'o - July 11, 2011, 4:06 a.m.
On Fri, Jul 01, 2011 at 11:27:52PM +0800, Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
> 
> 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>

Added to the ext4 tree, thanks.

							- Ted
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Patch

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 6ed859d..604b706 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4904,6 +4904,8 @@  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;
@@ -4952,5 +4954,6 @@  int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
 	}
 	range->len = trimmed * sb->s_blocksize;
 
+out:
 	return ret;
 }