Patch "ext4: be more strict when migrating to non-extent based file" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

ext4: be more strict when migrating to non-extent based file

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ext4-be-more-strict-when-migrating-to-non-extent-based-file.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eryu Guan <[email protected]>
Date: Fri, 3 Jul 2015 23:56:50 -0400
Subject: ext4: be more strict when migrating to non-extent based file

From: Eryu Guan <[email protected]>

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) blocks

This can be demostrated by

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

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

---
 fs/ext4/migrate.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

@@ -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
 				       EXT4_FEATURE_RO_COMPAT_BIGALLOC))
 		return -EOPNOTSUPP;
 
+	/*
+	 * 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) {
 			ret = -EOPNOTSUPP;
 			goto errout;
 		}

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/ext4-correctly-migrate-a-file-with-a-hole-at-the-beginning.patch queue-3.14/ext4-be-more-strict-when-migrating-to-non-extent-based-file.patch