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Message-Id: <1330690318-22627-1-git-send-email-lczerner@redhat.com>
Date: Fri, 2 Mar 2012 13:11:55 +0100
From: Lukas Czerner <lczerner@...hat.com>
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu, Lukas Czerner <lczerner@...hat.com>
Subject: [PATCH 1/4 v2] ext4: fix start and len arguments handling in ext4_trim_fs()
The overflow can happen when we are calling get_group_no_and_offset()
which stores the group number in the ext4_grpblk_t type which is
actually int. However when the blocknr is big enough the group number
might be bigger than ext4_grpblk_t resulting in overflow. This will
most likely happen with FITRIM 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.
Signed-off-by: Lukas Czerner <lczerner@...hat.com>
---
v2: Squash the 'don't forget to discard last block in a group' into this one
since this is the commit which reveals the bug.
fs/ext4/mballoc.c | 57 +++++++++++++++++++++++++++-------------------------
1 files changed, 30 insertions(+), 27 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cb990b2..16a3aeb 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4971,11 +4971,11 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
start = (e4b.bd_info->bb_first_free > start) ?
e4b.bd_info->bb_first_free : start;
- while (start < max) {
- start = mb_find_next_zero_bit(bitmap, max, start);
- if (start >= max)
+ while (start <= max) {
+ start = mb_find_next_zero_bit(bitmap, max + 1, start);
+ if (start > max)
break;
- next = mb_find_next_bit(bitmap, max, start);
+ next = mb_find_next_bit(bitmap, max + 1, start);
if ((next - start) >= minblocks) {
ext4_trim_extent(sb, start,
@@ -5027,37 +5027,36 @@ 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_cluster, last_cluster;
- 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_CLUSTERS_PER_GROUP(sb)))
+ if (unlikely(minlen > EXT4_CLUSTERS_PER_GROUP(sb)) ||
+ unlikely(start >= max_blks))
return -EINVAL;
- if (start + len <= first_data_blk)
+ if (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 */
+ /* Determine first and last group to examine based on start and end */
ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) start,
&first_group, &first_cluster);
- 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_cluster);
- last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
- last_cluster = EXT4_CLUSTERS_PER_GROUP(sb);
- if (first_group > last_group)
- return -EINVAL;
+ /* end now represents the last cluster to discard in this group */
+ end = EXT4_CLUSTERS_PER_GROUP(sb) - 1;
for (group = first_group; group <= last_group; group++) {
grp = ext4_get_group_info(sb, group);
@@ -5069,24 +5068,28 @@ 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).
+ * For all the groups except the last one, last cluster will
+ * always be EXT4_CLUSTERS_PER_GROUP(sb)-1, so we only need to
+ * change it for the last group, note that last_cluster is
+ * already computed earlier by ext4_get_group_no_and_offset()
*/
- if (first_cluster + len < EXT4_CLUSTERS_PER_GROUP(sb))
- last_cluster = first_cluster + len;
- len -= last_cluster - first_cluster;
+ if (group == last_group)
+ end = last_cluster;
if (grp->bb_free >= minlen) {
cnt = ext4_trim_all_free(sb, group, first_cluster,
- last_cluster, minlen);
+ end, minlen);
if (cnt < 0) {
ret = cnt;
break;
}
}
trimmed += cnt;
+
+ /*
+ * For every group except the first one, we are sure
+ * that the first cluster to discard will be cluster #0.
+ */
first_cluster = 0;
}
range->len = trimmed * sb->s_blocksize;
--
1.7.4.4
--
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