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Date: Fri, 2 Mar 2012 13:09:05 +0100
From: Lukas Czerner <lczerner@...hat.com>
To: linux-ext4@...r.kernel.org
Cc: Lukas Czerner <lczerner@...hat.com>, Jan Kara <jack@...e.cz>
Subject: [PATCH v2] ext3: fix start and len arguments handling in ext3_trim_fs()
The overflow might happen when passing blocknr into
ext3_get_group_no_and_offset(), because it expects type ext3_fsblk_t
which might be smaller than uint64_t. 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.
Signed-off-by: Lukas Czerner <lczerner@...hat.com>
Cc: Jan Kara <jack@...e.cz>
---
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/ext3/balloc.c | 77 +++++++++++++++++++++++++++--------------------------
1 files changed, 39 insertions(+), 38 deletions(-)
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index a203892..997da27 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1970,7 +1970,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
sbi = EXT3_SB(sb);
/* Walk through the whole group */
- while (start < max) {
+ while (start <= max) {
start = bitmap_search_next_usable_block(start, bitmap_bh, max);
if (start < 0)
break;
@@ -1980,7 +1980,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
* Allocate contiguous free extents by setting bits in the
* block bitmap
*/
- while (next < max
+ while (next <= max
&& claim_block(sb_bgl_lock(sbi, group),
next, bitmap_bh)) {
next++;
@@ -2091,73 +2091,74 @@ err_out:
*/
int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
{
- ext3_grpblk_t last_block, first_block, free_blocks;
- unsigned long first_group, last_group;
- unsigned long group, ngroups;
+ ext3_grpblk_t last_block, first_block;
+ unsigned long group, first_group, last_group;
struct ext3_group_desc *gdp;
struct ext3_super_block *es = EXT3_SB(sb)->s_es;
- uint64_t start, len, minlen, trimmed;
+ uint64_t start, minlen, end, trimmed = 0;
+ ext3_fsblk_t first_data_blk =
+ le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
int ret = 0;
- start = (range->start >> sb->s_blocksize_bits) +
- le32_to_cpu(es->s_first_data_block);
- len = range->len >> sb->s_blocksize_bits;
+ start = range->start >> sb->s_blocksize_bits;
+ end = start + (range->len >> sb->s_blocksize_bits) - 1;
minlen = range->minlen >> sb->s_blocksize_bits;
- trimmed = 0;
- if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
+ if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)) ||
+ unlikely(start >= max_blks))
return -EINVAL;
- if (start >= max_blks)
- return -EINVAL;
- if (start + len > max_blks)
- len = max_blks - start;
+ if (end >= max_blks)
+ end = max_blks - 1;
+ if (end <= first_data_blk)
+ goto out;
+ if (start < first_data_blk)
+ start = first_data_blk;
- ngroups = EXT3_SB(sb)->s_groups_count;
smp_rmb();
/* Determine first and last group to examine based on start and len */
ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
&first_group, &first_block);
- ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
+ ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
&last_group, &last_block);
- last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
- last_block = EXT3_BLOCKS_PER_GROUP(sb);
- if (first_group > last_group)
- return -EINVAL;
+ /* end now represents the last block to discard in this group */
+ end = EXT3_BLOCKS_PER_GROUP(sb) - 1;
for (group = first_group; group <= last_group; group++) {
gdp = ext3_get_group_desc(sb, group, NULL);
if (!gdp)
break;
- free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
- if (free_blocks < minlen)
- continue;
-
/*
* For all the groups except the last one, last block will
- * always be EXT3_BLOCKS_PER_GROUP(sb), so we only need to
- * change it for the last group in which case first_block +
- * len < EXT3_BLOCKS_PER_GROUP(sb).
+ * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
+ * change it for the last group, note that last_block is
+ * already computed earlier by ext3_get_group_no_and_offset()
*/
- if (first_block + len < EXT3_BLOCKS_PER_GROUP(sb))
- last_block = first_block + len;
- len -= last_block - first_block;
+ if (group == last_group)
+ end = last_block;
- ret = ext3_trim_all_free(sb, group, first_block,
- last_block, minlen);
- if (ret < 0)
- break;
+ if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
+ ret = ext3_trim_all_free(sb, group, first_block,
+ end, minlen);
+ if (ret < 0)
+ break;
+ trimmed += ret;
+ }
- trimmed += ret;
+ /*
+ * For every group except the first one, we are sure
+ * that the first block to discard will be block #0.
+ */
first_block = 0;
}
- if (ret >= 0)
+ if (ret > 0)
ret = 0;
- range->len = trimmed * sb->s_blocksize;
+out:
+ range->len = trimmed * sb->s_blocksize;
return ret;
}
--
1.7.4.4
--
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