Patchwork [1/4] ext4: fix trim length underflow with small trim length.

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Submitter Tao Ma
Date Feb. 9, 2011, 5:57 a.m.
Message ID <1297231048-3458-1-git-send-email-tm@tao.ma>
Download mbox | patch
Permalink /patch/82429/
State Accepted
Headers show

Comments

Tao Ma - Feb. 9, 2011, 5:57 a.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.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
---
 fs/ext4/mballoc.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

Patch

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 02cff4a..94e9f23 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4839,6 +4839,9 @@  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;
@@ -4883,5 +4886,6 @@  int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
 	}
 	range->len = trimmed * sb->s_blocksize;
 
+out:
 	return ret;
 }