From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tao Ma Subject: Re: [PATCH 1/4] ext4: fix trim length underflow with small trim length. Date: Fri, 01 Jul 2011 18:15:30 +0800 Message-ID: <4E0D9E42.3000606@tao.ma> References: <4E0C8B6C.8030403@tao.ma> <1309445439-3753-1-git-send-email-tm@tao.ma> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org To: Lukas Czerner Return-path: Received: from oproxy8-pub.bluehost.com ([69.89.22.20]:53348 "HELO oproxy8-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755677Ab1GAKPs (ORCPT ); Fri, 1 Jul 2011 06:15:48 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi Lukas, On 07/01/2011 05:45 PM, Lukas Czerner wrote: > On Thu, 30 Jun 2011, Tao Ma wrote: > >> From: Tao Ma >> >> 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. > > Hi Tao, > > thanks for the resend! > >> >> 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 6ed859d..2336424 100644 >> --- a/fs/ext4/mballoc.c >> +++ b/fs/ext4/mballoc.c >> @@ -4904,6 +4904,9 @@ 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; > > We should really return -EINVAL in case that start is beyond the > filesystem. However we can not return -EINVAL in case that start+len is > before the first data block, because it would require user to know fs > internals. uh, actually I have checked what ext3 does and in case of start > block_count, ext3 returns 0, not EINVAL and I made it to work like ext3. So we should change it also? Thanks Tao > > So simply doing this, should be enough: > > if (start + len <= first_data_blk) > goto out; > > and the code later > > if (first_group > last_group) > return -EINVAL; > > will handle the rest. > > Thanks! > -Lukas > > >> if (start < first_data_blk) { >> len -= first_data_blk - start; >> start = first_data_blk; >> @@ -4952,5 +4955,6 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) >> } >> range->len = trimmed * sb->s_blocksize; >> >> +out: >> return ret; >> } >> >