linux/fs/ext4
Lukas Czerner d2dc317d56 ext4: fix data corruption caused by unwritten and delayed extents
Currently it is possible to lose whole file system block worth of data
when we hit the specific interaction with unwritten and delayed extents
in status extent tree.

The problem is that when we insert delayed extent into extent status
tree the only way to get rid of it is when we write out delayed buffer.
However there is a limitation in the extent status tree implementation
so that when inserting unwritten extent should there be even a single
delayed block the whole unwritten extent would be marked as delayed.

At this point, there is no way to get rid of the delayed extents,
because there are no delayed buffers to write out. So when a we write
into said unwritten extent we will convert it to written, but it still
remains delayed.

When we try to write into that block later ext4_da_map_blocks() will set
the buffer new and delayed and map it to invalid block which causes
the rest of the block to be zeroed loosing already written data.

For now we can fix this by simply not allowing to set delayed status on
written extent in the extent status tree. Also add WARN_ON() to make
sure that we notice if this happens in the future.

This problem can be easily reproduced by running the following xfs_io.

xfs_io -f -c "pwrite -S 0xaa 4096 2048" \
          -c "falloc 0 131072" \
          -c "pwrite -S 0xbb 65536 2048" \
          -c "fsync" /mnt/test/fff

echo 3 > /proc/sys/vm/drop_caches
xfs_io -c "pwrite -S 0xdd 67584 2048" /mnt/test/fff

This can be theoretically also reproduced by at random by running fsx,
but it's not very reliable, though on machines with bigger page size
(like ppc) this can be seen more often (especially xfstest generic/127)

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
2015-05-02 21:36:55 -04:00
..
acl.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
acl.h ext2/3/4: use generic posix ACL infrastructure 2014-01-25 23:58:19 -05:00
balloc.c ext4: remove unnecessary lock/unlock of i_block_reservation_lock 2015-04-03 00:02:53 -04:00
bitmap.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
block_validity.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
crypto_fname.c ext4 crypto: add padding to filenames before encrypting 2015-05-01 16:56:50 -04:00
crypto_key.c ext4 crypto: add padding to filenames before encrypting 2015-05-01 16:56:50 -04:00
crypto_policy.c ext4 crypto: add padding to filenames before encrypting 2015-05-01 16:56:50 -04:00
crypto.c ext4 crypto: add ext4 encryption facilities 2015-04-12 00:43:56 -04:00
dir.c ext4 crypto: simplify and speed up filename encryption 2015-05-01 16:56:45 -04:00
ext4_crypto.h ext4 crypto: add padding to filenames before encrypting 2015-05-01 16:56:50 -04:00
ext4_extents.h ext4: teach ext4_ext_find_extent() to realloc path if necessary 2014-09-01 14:40:09 -04:00
ext4_jbd2.c ext4: fix over-defensive complaint after journal abort 2014-10-01 22:23:15 -04:00
ext4_jbd2.h ext4: don't use MAXQUOTAS value 2014-09-11 11:15:15 -04:00
ext4.h ext4 crypto: remove duplicated encryption mode definitions 2015-05-02 10:29:22 -04:00
extents_status.c ext4: fix data corruption caused by unwritten and delayed extents 2015-05-02 21:36:55 -04:00
extents_status.h ext4: introduce aging to extent status tree 2014-11-25 11:55:24 -05:00
extents.c ext4 crypto: implement the ext4 encryption write path 2015-04-12 00:55:10 -04:00
file.c ext4 crypto: implement the ext4 decryption read path 2015-04-12 00:56:10 -04:00
fsync.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
hash.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
ialloc.c ext4 crypto: enable encryption feature flag 2015-04-16 01:56:00 -04:00
indirect.c Ext4 bug fixes for 3.20. We also reserved code points for encryption 2015-02-22 18:05:13 -08:00
inline.c ext4 crypto: insert encrypted filenames into a leaf directory block 2015-04-12 00:56:28 -04:00
inode.c ext4: fix data corruption caused by unwritten and delayed extents 2015-05-02 21:36:55 -04:00
ioctl.c ext4 crypto: add encryption policy and password salt support 2015-04-11 07:48:01 -04:00
Kconfig ext4 crypto: do not select from EXT4_FS_ENCRYPTION 2015-05-02 10:29:19 -04:00
Makefile ext4 crypto: filename encryption facilities 2015-04-12 00:56:17 -04:00
mballoc.c ext4: Remove an unnecessary check for NULL before iput() 2014-11-25 20:01:37 -05:00
mballoc.h ext4: remove unused ac_ex_scanned 2014-02-20 13:32:10 -05:00
migrate.c ext4: update comments regarding ext4_delete_inode() 2014-11-25 16:17:29 -05:00
mmp.c ext4: Replace open coded mdata csum feature to helper function 2014-10-13 03:36:16 -04:00
move_extent.c move_extent_per_page(): get rid of unused w_flags 2014-12-17 06:43:56 -05:00
namei.c ext4 crypto: simplify and speed up filename encryption 2015-05-01 16:56:45 -04:00
page-io.c ext4 crypto: implement the ext4 encryption write path 2015-04-12 00:55:10 -04:00
readpage.c ext4 crypto: implement the ext4 decryption read path 2015-04-12 00:56:10 -04:00
resize.c ext4: prevent online resize with backup superblock 2014-12-26 23:58:21 -05:00
super.c ext4 crypto: enable encryption feature flag 2015-04-16 01:56:00 -04:00
symlink.c ext4 crypto: simplify and speed up filename encryption 2015-05-01 16:56:45 -04:00
truncate.h ext4: move common truncate functions to header file 2011-06-27 19:16:04 -04:00
xattr_security.c Merge branch 'for_linus' into for_linus_merged 2012-01-10 11:54:07 -05:00
xattr_trusted.c ext2/3/4: delete unneeded includes of module.h 2012-01-09 13:52:10 +01:00
xattr_user.c ext2/3/4: delete unneeded includes of module.h 2012-01-09 13:52:10 +01:00
xattr.c ext4: remove useless condition in if statement. 2015-04-02 23:50:48 -04:00
xattr.h ext4 crypto: add encryption xattr support 2015-04-11 07:47:00 -04:00