[PATCH 3.16.y-ckt 007/118] ext4: be more strict when migrating to non-extent based file

From: Luis Henriques
Date: Wed Aug 12 2015 - 05:41:36 EST

3.16.7-ckt16 -stable review patch. If anyone has any objections, please let me know.


From: Eryu Guan <guaneryu@xxxxxxxxx>

commit d6f123a9297496ad0b6335fe881504c4b5b2a5e5 upstream.

Currently the check in ext4_ind_migrate() is not enough before doing the
real conversion:

a) delayed allocated extents could bypass the check on eh->eh_entries
and eh->eh_depth

This can be demonstrated by this script

xfs_io -fc "pwrite 0 4k" -c "pwrite 8k 4k" /mnt/ext4/testfile
chattr -e /mnt/ext4/testfile

where testfile has two extents but still be converted to non-extent
based file format.

b) only extent length is checked but not the offset, which would result
in data lose (delalloc) or fs corruption (nodelalloc), because
non-extent based file only supports at most (12 + 2^10 + 2^20 + 2^30)

This can be demostrated by

xfs_io -fc "pwrite 5T 4k" /mnt/ext4/testfile
chattr -e /mnt/ext4/testfile

If delalloc is enabled, dmesg prints
EXT4-fs warning (device dm-4): ext4_block_to_path:105: block 1342177280 > max in inode 53
EXT4-fs (dm-4): Delayed block allocation failed for inode 53 at logical offset 1342177280 with max blocks 1 with error 5
EXT4-fs (dm-4): This should not happen!! Data will be lost

If delalloc is disabled, e2fsck -nf shows corruption
Inode 53, i_size is 5497558142976, should be 4096. Fix? no

Fix the two issues by

a) forcing all delayed allocation blocks to be allocated before checking
eh->eh_depth and eh->eh_entries
b) limiting the last logical block of the extent is within direct map

Signed-off-by: Eryu Guan <guaneryu@xxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
fs/ext4/migrate.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index ec092437d3e0..c39329ac545b 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -616,6 +616,7 @@ int ext4_ind_migrate(struct inode *inode)
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_extent *ex;
unsigned int i, len;
+ ext4_lblk_t end;
ext4_fsblk_t blk;
handle_t *handle;
int ret;
@@ -629,6 +630,14 @@ int ext4_ind_migrate(struct inode *inode)

+ /*
+ * In order to get correct extent info, force all delayed allocation
+ * blocks to be allocated, otherwise delayed allocation blocks may not
+ * be reflected and bypass the checks on extent header.
+ */
+ if (test_opt(inode->i_sb, DELALLOC))
+ ext4_alloc_da_blocks(inode);
handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
if (IS_ERR(handle))
return PTR_ERR(handle);
@@ -650,7 +659,8 @@ int ext4_ind_migrate(struct inode *inode)
else {
len = le16_to_cpu(ex->ee_len);
blk = ext4_ext_pblock(ex);
- if (len > EXT4_NDIR_BLOCKS) {
+ end = le32_to_cpu(ex->ee_block) + len - 1;
+ if (end >= EXT4_NDIR_BLOCKS) {
goto errout;
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