[BUG] When mounting certain crafted image, btrfs will trigger kernel BUG_ON() when try to recover balance: ------ ------------[ cut here ]------------ kernel BUG at fs/btrfs/extent-tree.c:8956! invalid opcode: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 PID: 662 Comm: mount Not tainted 4.18.0-rc1-custom+ #10 RIP: 0010:walk_up_proc+0x336/0x480 [btrfs] RSP: 0018:ffffb53540c9b890 EFLAGS: 00010202 Call Trace: walk_up_tree+0x172/0x1f0 [btrfs] btrfs_drop_snapshot+0x3a4/0x830 [btrfs] merge_reloc_roots+0xe1/0x1d0 [btrfs] btrfs_recover_relocation+0x3ea/0x420 [btrfs] open_ctree+0x1af3/0x1dd0 [btrfs] btrfs_mount_root+0x66b/0x740 [btrfs] mount_fs+0x3b/0x16a vfs_kern_mount.part.9+0x54/0x140 btrfs_mount+0x16d/0x890 [btrfs] mount_fs+0x3b/0x16a vfs_kern_mount.part.9+0x54/0x140 do_mount+0x1fd/0xda0 ksys_mount+0xba/0xd0 __x64_sys_mount+0x21/0x30 do_syscall_64+0x60/0x210 entry_SYSCALL_64_after_hwframe+0x49/0xbe ---[ end trace d4344e4deee03435 ]--- ------
[CAUSE] Another extent tree corruption. In this particular case, tree reloc root's owner is DATA_RELOC_TREE (should be TREE_RELOC_TREE), thus its backref is corrupted and we failed the owner check in walk_up_tree(). [FIX] It's pretty hard to take care of every extent tree corruption, but at least we can remove such BUG_ON() and exit more gracefully. And since in this particular image, DATA_RELOC_TREE and TREE_RELOC_TREE shares the same root (which is obviously invalid), we needs to make __del_reloc_root() more robust to detect such invalid share to avoid possible NULL dereference as root->node can be NULL in this case. Link: https://bugzilla.kernel.org/show_bug.cgi?id=200411 Reported-by: Xu Wen <wen...@gatech.edu> Signed-off-by: Qu Wenruo <w...@suse.com> --- changelog: v2: Merge the same error message output code into one block and add label for the goto usage. v2.1: Fix compile error. --- fs/btrfs/extent-tree.c | 18 ++++++++++++------ fs/btrfs/relocation.c | 2 +- 2 files changed, 13 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 3578fa5b30ef..697dffc9d598 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -8939,15 +8939,14 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans, if (eb == root->node) { if (wc->flags[level] & BTRFS_BLOCK_FLAG_FULL_BACKREF) parent = eb->start; - else - BUG_ON(root->root_key.objectid != - btrfs_header_owner(eb)); + else if (root->root_key.objectid != btrfs_header_owner(eb)) + goto owner_mismatch; } else { if (wc->flags[level + 1] & BTRFS_BLOCK_FLAG_FULL_BACKREF) parent = path->nodes[level + 1]->start; - else - BUG_ON(root->root_key.objectid != - btrfs_header_owner(path->nodes[level + 1])); + else if (root->root_key.objectid != + btrfs_header_owner(path->nodes[level + 1])) + goto owner_mismatch; } btrfs_free_tree_block(trans, root, eb, parent, wc->refs[level] == 1); @@ -8955,6 +8954,11 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans, wc->refs[level] = 0; wc->flags[level] = 0; return 0; + +owner_mismatch: + btrfs_err_rl(fs_info, "unexpected tree owner, have %llu expect %llu", + btrfs_header_owner(eb), root->root_key.objectid); + return -EUCLEAN; } static noinline int walk_down_tree(struct btrfs_trans_handle *trans, @@ -9008,6 +9012,8 @@ static noinline int walk_up_tree(struct btrfs_trans_handle *trans, ret = walk_up_proc(trans, root, path, wc); if (ret > 0) return 0; + if (ret < 0) + return ret; if (path->locks[level]) { btrfs_tree_unlock_rw(path->nodes[level], diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index be94c65bb4d2..5ee49b796815 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1321,7 +1321,7 @@ static void __del_reloc_root(struct btrfs_root *root) struct mapping_node *node = NULL; struct reloc_control *rc = fs_info->reloc_ctl; - if (rc) { + if (rc && root->node) { spin_lock(&rc->reloc_root_tree.lock); rb_node = tree_search(&rc->reloc_root_tree.rb_root, root->node->start); -- 2.18.0
