From 07cce5cf3b489419aa8e87f48a55f4e190a30876 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 19 Aug 2020 14:35:49 +0800 Subject: [PATCH] btrfs: extent-tree: kill the BUG_ON() in insert_inline_extent_backref() [BUG] With a crafted image, btrfs can panic at insert_inline_extent_backref(): kernel BUG at fs/btrfs/extent-tree.c:1857! invalid opcode: 0000 [#1] SMP PTI CPU: 0 PID: 1117 Comm: btrfs-transacti Not tainted 5.0.0-rc8+ #9 RIP: 0010:insert_inline_extent_backref+0xcc/0xe0 RSP: 0018:ffffac4dc1287be8 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000000001 RDX: 0000000000001000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffac4dc1287c28 R08: ffffac4dc1287ab8 R09: ffffac4dc1287ac0 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffff8febef88a540 R14: ffff8febeaa7bc30 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8febf7a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f663ace94c0 CR3: 0000000235698006 CR4: 00000000000206f0 Call Trace: ? _cond_resched+0x1a/0x50 __btrfs_inc_extent_ref.isra.64+0x7e/0x240 ? btrfs_merge_delayed_refs+0xa5/0x330 __btrfs_run_delayed_refs+0x653/0x1120 btrfs_run_delayed_refs+0xdb/0x1b0 btrfs_commit_transaction+0x52/0x950 ? start_transaction+0x94/0x450 transaction_kthread+0x163/0x190 kthread+0x105/0x140 ? btrfs_cleanup_transaction+0x560/0x560 ? kthread_destroy_worker+0x50/0x50 ret_from_fork+0x35/0x40 Modules linked in: ---[ end trace 2ad8b3de903cf825 ]--- [CAUSE] Due to extent tree corruption (still valid by itself, but bad cross ref), we can allocate an extent which is still in extent tree. The offending tree block of that case is from csum tree. The newly allocated tree block is also for csum tree. Then we will try to insert a tree block ref for the existing tree block ref. For a tree extent item, tree block can never be shared directly by the same tree twice. We have such BUG_ON() to prevent such problem, but this is not a proper error handling. [FIX] Replace that BUG_ON() with proper error message and leaf dump for debug build. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202829 Reviewed-by: Nikolay Borisov Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/extent-tree.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 40e5b41e91cc..7b61b7b5122f 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -1177,7 +1177,22 @@ int insert_inline_extent_backref(struct btrfs_trans_handle *trans, num_bytes, parent, root_objectid, owner, offset, 1); if (ret == 0) { - BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID); + /* + * We're adding refs to a tree block we already own, this + * should not happen at all. + */ + if (owner < BTRFS_FIRST_FREE_OBJECTID) { + btrfs_crit(trans->fs_info, +"adding refs to an existing tree ref, bytenr %llu num_bytes %llu root_objectid %llu", + bytenr, num_bytes, root_objectid); + if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) { + WARN_ON(1); + btrfs_crit(trans->fs_info, + "path->slots[0]=%d path->nodes[0]:", path->slots[0]); + btrfs_print_leaf(path->nodes[0]); + } + return -EUCLEAN; + } update_inline_extent_backref(path, iref, refs_to_add, extent_op, NULL); } else if (ret == -ENOENT) { @@ -1397,6 +1412,9 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans, /* * __btrfs_inc_extent_ref - insert backreference for a given extent * + * The counterpart is in __btrfs_free_extent(), with examples and more details + * how it works. + * * @trans: Handle of transaction * * @node: The delayed ref node used to get the bytenr/length for