btrfs-progs/check
Qu Wenruo 3a2d040070 btrfs-progs: check/lowmem: Fix access on uninitialized memory
[BUG]
There are some reports on fsck/001 test segfault failure with lowmem mode.

While I failed to reproduce it, valgrind still catches it with the
following output:

  Delete backref in extent [12845056 1048576]
  ERROR: file extent [257, 0] has unaligned disk bytenr: 755944791, should be aligned to 4096
  ERROR: file extent[257 0] root 5 owner 5 backref lost
  Deleted root 5 item[257, 108, 0]
  ==29080== Conditional jump or move depends on uninitialised value(s)
  ==29080==    at 0x1A81D7: btrfs_release_path (ctree.c:97)
  ==29080==    by 0x192C33: repair_extent_data_item (mode-lowmem.c:3330)
  ==29080==    by 0x1962FF: check_leaf_items (mode-lowmem.c:4696)
  ==29080==    by 0x196ABF: walk_down_tree (mode-lowmem.c:4858)
  ==29080==    by 0x197762: check_btrfs_root (mode-lowmem.c:5157)
  ==29080==    by 0x198335: check_chunks_and_extents_lowmem (mode-lowmem.c:5450)
  ==29080==    by 0x166414: do_check_chunks_and_extents (main.c:8829)
  ==29080==    by 0x169CF7: cmd_check (main.c:10313)
  ==29080==    by 0x11CDC6: cmd_execute (commands.h:125)
  ==29080==    by 0x11D712: main (btrfs.c:386)
  ==29080==

[CAUSE]
In repair_extent_data_item() if we find unaligned file extent, we just
delete it and kick in hole punch procedure.

The problem is, file extent deletion is done before initializing @path.
And when the deletion is done without problem, we will goto out tag,
which will release @path, containing uninitialized values, and
triggering segfault.

[FIX]
Don't try to abort trans nor free path if we're going through file
extent deletion routine.

Fixes: 0617bde3bc ("btrfs-progs: lowmem: delete unaligned bytes extent data under repair")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-03-31 18:37:36 +02:00
..
common.h btrfs-progs: check: move device_record to main.c 2019-10-14 17:27:41 +02:00
main.c btrfs-progs: fix hole error output in fsck 2020-03-31 18:37:35 +02:00
mode-common.c btrfs-progs: move name hashing functions to ctree.h and delete hash.h 2020-03-31 18:37:35 +02:00
mode-common.h btrfs-progs: check/original: Fix inode mode in subvolume trees 2019-11-18 19:21:07 +01:00
mode-lowmem.c btrfs-progs: check/lowmem: Fix access on uninitialized memory 2020-03-31 18:37:36 +02:00
mode-lowmem.h btrfs-progs: check/lowmem: Check and repair root generation 2019-09-04 16:06:50 +02:00
mode-original.h btrfs-progs: check/original: Add check and repair for invalid inode generation 2019-11-18 19:21:07 +01:00
qgroup-verify.c btrfs-progs: qgroup-verify: Remove duplicated message in report_qgroups 2020-03-31 18:37:36 +02:00
qgroup-verify.h btrfs-progs: move qgroup-verify.[ch] to check/ 2019-10-14 17:27:35 +02:00