| Submitter | Lukas Czerner |
|---|---|
| Date | Sept. 5, 2011, 2:34 p.m. |
| Message ID | <1315233249-27167-1-git-send-email-lczerner@redhat.com> |
| Download | mbox | patch |
| Permalink | /patch/113377/ |
| State | Superseded |
| Headers | show |
Comments
Hi Lucas, On 09/05/2011 10:34 PM, Lukas Czerner wrote: > In ext4_trim_fs it is possible that start+len might overflow. Fix it by > decrementing the len so that start+len equals to the file system size in > the worst case. Actually start + len can never overflow since they are changed by start = range->start >> sb->s_blocksize_bits; len = range->len >> sb->s_blocksize_bits; range->start and range->len are u64, and after they are shifted with blocksize_bits, start+len(ext4_fsblk_t is also 64bit) can't overflow. Thanks Tao > > Signed-off-by: Lukas Czerner <lczerner@redhat.com> > --- > fs/ext4/mballoc.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > index 17a5a57..d86dc14 100644 > --- a/fs/ext4/mballoc.c > +++ b/fs/ext4/mballoc.c > @@ -4952,14 +4952,18 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) > uint64_t start, len, minlen, trimmed = 0; > ext4_fsblk_t first_data_blk = > le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block); > + ext4_fsblk_t max_blks = ext4_blocks_count(EXT4_SB(sb)->s_es); > int ret = 0; > > start = range->start >> sb->s_blocksize_bits; > len = range->len >> sb->s_blocksize_bits; > minlen = range->minlen >> sb->s_blocksize_bits; > > - if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb))) > + if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)) || > + unlikely(start > max_blks)) > return -EINVAL; > + if (unlikely(len > max_blks)) > + len = max_blks - start; > if (start + len <= first_data_blk) > goto out; > if (start < first_data_blk) { -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 6 Sep 2011, Tao Ma wrote: > Hi Lucas, > On 09/05/2011 10:34 PM, Lukas Czerner wrote: > > In ext4_trim_fs it is possible that start+len might overflow. Fix it by > > decrementing the len so that start+len equals to the file system size in > > the worst case. > Actually start + len can never overflow since they are changed by > start = range->start >> sb->s_blocksize_bits; > len = range->len >> sb->s_blocksize_bits; > > range->start and range->len are u64, and after they are shifted with > blocksize_bits, start+len(ext4_fsblk_t is also 64bit) can't overflow. > > Thanks > Tao Hi Tao, I am really sorry for badly worded commit description. The problem is real, however as you pointed out the overflow does not happen in len+start addition but in ext4_get_group_no_and_offset() when we are storing group number into the ext4_group_t which is 32 bit long, but the result of do_div() might be bigger than that. I will rephrase the commit description and resend the patch. I was doing similar thing for xfs and I have just used almost the same description which is wrong. Thanks! -Lukas > > > > Signed-off-by: Lukas Czerner <lczerner@redhat.com> > > --- > > fs/ext4/mballoc.c | 6 +++++- > > 1 files changed, 5 insertions(+), 1 deletions(-) > > > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > > index 17a5a57..d86dc14 100644 > > --- a/fs/ext4/mballoc.c > > +++ b/fs/ext4/mballoc.c > > @@ -4952,14 +4952,18 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) > > uint64_t start, len, minlen, trimmed = 0; > > ext4_fsblk_t first_data_blk = > > le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block); > > + ext4_fsblk_t max_blks = ext4_blocks_count(EXT4_SB(sb)->s_es); > > int ret = 0; > > > > start = range->start >> sb->s_blocksize_bits; > > len = range->len >> sb->s_blocksize_bits; > > minlen = range->minlen >> sb->s_blocksize_bits; > > > > - if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb))) > > + if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)) || > > + unlikely(start > max_blks)) > > return -EINVAL; > > + if (unlikely(len > max_blks)) > > + len = max_blks - start; > > if (start + len <= first_data_blk) > > goto out; > > if (start < first_data_blk) { > >
Patch
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 17a5a57..d86dc14 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4952,14 +4952,18 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) uint64_t start, len, minlen, trimmed = 0; ext4_fsblk_t first_data_blk = le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block); + ext4_fsblk_t max_blks = ext4_blocks_count(EXT4_SB(sb)->s_es); int ret = 0; start = range->start >> sb->s_blocksize_bits; len = range->len >> sb->s_blocksize_bits; minlen = range->minlen >> sb->s_blocksize_bits; - if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb))) + if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)) || + unlikely(start > max_blks)) return -EINVAL; + if (unlikely(len > max_blks)) + len = max_blks - start; if (start + len <= first_data_blk) goto out; if (start < first_data_blk) {
In ext4_trim_fs it is possible that start+len might overflow. Fix it by decrementing the len so that start+len equals to the file system size in the worst case. Signed-off-by: Lukas Czerner <lczerner@redhat.com> --- fs/ext4/mballoc.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-)