On Fri, 1 Jul 2011, Tao Ma wrote:
> Hi Lukas,
> On 07/01/2011 05:45 PM, Lukas Czerner wrote:
> > On Thu, 30 Jun 2011, Tao Ma wrote:
> >
> >> From: Tao Ma <boyu.mt@xxxxxxxxxx>
> >>
> >> 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 <boyu.mt@xxxxxxxxxx>
> >> ---
> >> 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?
I have already sent a patch a while ago. It should be in Jan's queue.
-Lukas
>
> 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;
> >> }
> >>
> >
>
>
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