57949d033a
[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 3d0174f78e72 ("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: 3d0174f78e72 ("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>
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.