On Wed, 7 Sep 2011, Lukas Czerner wrote: > The overflow can happen when we are calling get_group_no_and_offset() > which stores the result of do_div() in 32 bit long type. However the > result might be bigger than that if big blocknr is passed in. This will > most likely happen when calling FITRIM with the default argument len = > ULLONG_MAX. > > Fix this by using "end" variable instead of "start+len" as it is easier > to get right and specifically check that the end is not beyond the end > of the file system, so we are sure that the result of > get_group_no_and_offset() will not overflow. Otherwise truncate it to > the size of the file system. Any comments on this ? Note that the test case will be in xfstests soon. http://www.spinics.net/lists/xfs/msg07251.html Thanks! -Lukas > > Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx> > --- > v2 - Change commit description to better describe the problem > v3 - Use end instead of start+len, rework the fix > > fs/ext4/mballoc.c | 43 +++++++++++++++++++++++-------------------- > 1 files changed, 23 insertions(+), 20 deletions(-) > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > index 17a5a57..fa8b14b 100644 > --- a/fs/ext4/mballoc.c > +++ b/fs/ext4/mballoc.c > @@ -4946,37 +4946,36 @@ out: > int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) > { > struct ext4_group_info *grp; > - ext4_group_t first_group, last_group; > - ext4_group_t group, ngroups = ext4_get_groups_count(sb); > + ext4_group_t group, first_group, last_group; > ext4_grpblk_t cnt = 0, first_block, last_block; > - uint64_t start, len, minlen, trimmed = 0; > + uint64_t start, end, 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; > + end = start + (range->len >> sb->s_blocksize_bits) - 1; > 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 (start + len <= first_data_blk) > + if (unlikely(end >= max_blks)) > + end = max_blks - 1; > + if (end <= first_data_blk) > goto out; > - if (start < first_data_blk) { > - len -= first_data_blk - start; > + if (start < first_data_blk) > start = first_data_blk; > - } > > /* Determine first and last group to examine based on start and len */ > ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) start, > &first_group, &first_block); > - ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) (start + len), > + ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) end, > &last_group, &last_block); > - last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group; > - last_block = EXT4_BLOCKS_PER_GROUP(sb); > > - if (first_group > last_group) > - return -EINVAL; > + /* The last block to discard in the group */ > + end = EXT4_BLOCKS_PER_GROUP(sb); > > for (group = first_group; group <= last_group; group++) { > grp = ext4_get_group_info(sb, group); > @@ -4990,22 +4989,26 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) > /* > * For all the groups except the last one, last block will > * always be EXT4_BLOCKS_PER_GROUP(sb), so we only need to > - * change it for the last group in which case start + > - * len < EXT4_BLOCKS_PER_GROUP(sb). > + * change it for the last group, note that last_block is > + * already computed earlier by ext4_get_group_no_and_offset() > */ > - if (first_block + len < EXT4_BLOCKS_PER_GROUP(sb)) > - last_block = first_block + len; > - len -= last_block - first_block; > + if (group == last_group) > + end = last_block; > > if (grp->bb_free >= minlen) { > cnt = ext4_trim_all_free(sb, group, first_block, > - last_block, minlen); > + end, minlen); > if (cnt < 0) { > ret = cnt; > break; > } > } > trimmed += cnt; > + > + /* > + * For every group except the first one, we are sure > + * that the first block to discard will be block #0. > + */ > first_block = 0; > } > range->len = trimmed * sb->s_blocksize; > -- -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
