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Qu Wenruo 57949d033a btrfs: qgroup: Check bg while resuming relocation to avoid NULL pointer dereference 
[BUG]
When mounting a fs with reloc tree and has qgroup enabled, it can cause
NULL pointer dereference at mount time:

  BUG: kernel NULL pointer dereference, address: 00000000000000a8
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] PREEMPT SMP NOPTI
  RIP: 0010:btrfs_qgroup_add_swapped_blocks+0x186/0x300 [btrfs]
  Call Trace:
   replace_path.isra.23+0x685/0x900 [btrfs]
   merge_reloc_root+0x26e/0x5f0 [btrfs]
   merge_reloc_roots+0x10a/0x1a0 [btrfs]
   btrfs_recover_relocation+0x3cd/0x420 [btrfs]
   open_ctree+0x1bc8/0x1ed0 [btrfs]
   btrfs_mount_root+0x544/0x680 [btrfs]
   legacy_get_tree+0x34/0x60
   vfs_get_tree+0x2d/0xf0
   fc_mount+0x12/0x40
   vfs_kern_mount.part.12+0x61/0xa0
   vfs_kern_mount+0x13/0x20
   btrfs_mount+0x16f/0x860 [btrfs]
   legacy_get_tree+0x34/0x60
   vfs_get_tree+0x2d/0xf0
   do_mount+0x81f/0xac0
   ksys_mount+0xbf/0xe0
   __x64_sys_mount+0x25/0x30
   do_syscall_64+0x65/0x240
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

[CAUSE]
In btrfs_recover_relocation(), we don't have enough info to determine
which block group we're relocating, but only to merge existing reloc
trees.

Thus in btrfs_recover_relocation(), rc->block_group is NULL.
btrfs_qgroup_add_swapped_blocks() hasn't taken this into consideration,
and causes a NULL pointer dereference.

The bug is introduced by commit 3d0174f78e ("btrfs: qgroup: Only trace
data extents in leaves if we're relocating data block group"), and
later qgroup refactoring still keeps this optimization.

[FIX]
Thankfully in the context of btrfs_recover_relocation(), there is no
other progress can modify tree blocks, thus those swapped tree blocks
pair will never affect qgroup numbers, no matter whatever we set for
block->trace_leaf.

So we only need to check if @bg is NULL before accessing @bg->flags.

Reported-by: Juan Erbes <jerbes@gmail.com>
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1134806
Fixes: 3d0174f78e ("btrfs: qgroup: Only trace data extents in leaves if we're relocating data block group")
CC: stable@vger.kernel.org # 4.20+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-05-28 18:54:10 +02:00
arch A small number of ARM fixes 2019-04-28 10:50:57 -07:00
block bfq: update internal depth state when queue depth changes 2019-04-13 19:08:22 -06:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto crypto: lrw - Fix atomic sleep when walking skcipher 2019-04-18 22:13:46 +08:00
Documentation mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model 2019-04-26 09:18:05 -07:00
drivers 5.1 Third RC pull request 2019-04-28 10:00:45 -07:00
fs btrfs: qgroup: Check bg while resuming relocation to avoid NULL pointer dereference 2019-05-28 18:54:10 +02:00
include btrfs: trace: Introduce trace events for all btrfs tree locking events 2019-04-29 19:02:43 +02:00
init init: initialize jump labels before command line option parsing 2019-04-19 09:46:05 -07:00
ipc Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
kernel Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-04-27 10:18:40 -07:00
lib lib/test_vmalloc.c: do not create cpumask_t variable on stack 2019-04-26 09:18:05 -07:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
mm mm/page_alloc.c: fix never set ALLOC_NOFRAGMENT flag 2019-04-26 09:18:05 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-24 16:18:59 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-11 08:54:01 -07:00
scripts locking/atomics: Don't assume that scripts are executable 2019-04-19 14:21:43 +02:00
security Merge branch 'for-5.1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2019-04-19 18:03:55 -07:00
sound ALSA: hda/realtek - add two more pin configuration sets to quirk table 2019-04-17 10:41:38 +02:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-24 16:18:59 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM: fix spectrev1 gadgets 2019-04-16 15:38:07 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-04-12 12:49:54 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap Update Nicolas Pitre's email address 2019-04-02 18:12:44 -10:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS LED update for 5.1-rc7. 2019-04-24 16:15:38 -07:00
Makefile Linux 5.1-rc7 2019-04-28 17:04:13 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.