On 10.07.19 г. 11:02 ч., Qu Wenruo wrote: > [BUG] > With crafted image, btrfs can panic at btrfs_del_csums(). > kernel BUG at fs/btrfs/ctree.c:3188! > invalid opcode: 0000 [#1] SMP PTI > CPU: 0 PID: 1156 Comm: btrfs-transacti Not tainted 5.0.0-rc8+ #9 > RIP: 0010:btrfs_set_item_key_safe+0x16c/0x180 > Code: b7 48 8d 7d bf 4c 89 fe 48 89 45 c8 0f b6 45 b6 88 45 c7 48 8b 45 ae 48 89 45 bf e8 ce f2 ff ff 85 c0 0f 8f 48 ff ff ff 0f 0b <0f> 0b e8 dd 8d be ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 66 66 > RSP: 0018:ffff976141257ab8 EFLAGS: 00010202 > RAX: 0000000000000001 RBX: ffff898a6b890930 RCX: 0000000004b70000 > RDX: 0000000000000000 RSI: ffff976141257bae RDI: ffff976141257acf > RBP: ffff976141257b10 R08: 0000000000001000 R09: ffff9761412579a8 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff976141257abe > R13: 0000000000000003 R14: ffff898a6a8be578 R15: ffff976141257bae > FS: 0000000000000000(0000) GS:ffff898a77a00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f779d9cd624 CR3: 000000022b2b4006 CR4: 00000000000206f0 > Call Trace: > truncate_one_csum+0xac/0xf0 > btrfs_del_csums+0x24f/0x3a0 > __btrfs_free_extent.isra.72+0x5a7/0xbe0 > __btrfs_run_delayed_refs+0x539/0x1120 > 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 93bf9db00e6c374e ]--- > > [CAUSE] > This crafted image has a very tricky key order corruption: > > checksum tree key (CSUM_TREE ROOT_ITEM 0) > node 29741056 level 1 items 14 free 107 generation 19 owner CSUM_TREE > ... > key (EXTENT_CSUM EXTENT_CSUM 73785344) block 29757440 gen 19 > key (EXTENT_CSUM EXTENT_CSUM 77594624) block 29753344 gen 19 > ... > > leaf 29757440 items 5 free space 150 generation 19 owner CSUM_TREE > item 0 key (EXTENT_CSUM EXTENT_CSUM 73785344) itemoff 2323 itemsize 1672 > range start 73785344 end 75497472 length 1712128 > item 1 key (EXTENT_CSUM EXTENT_CSUM 75497472) itemoff 2319 itemsize 4 > range start 75497472 end 75501568 length 4096 > item 2 key (EXTENT_CSUM EXTENT_CSUM 75501568) itemoff 579 itemsize 1740 > range start 75501568 end 77283328 length 1781760 > item 3 key (EXTENT_CSUM EXTENT_CSUM 77283328) itemoff 575 itemsize 4 > range start 77283328 end 77287424 length 4096 > item 4 key (EXTENT_CSUM EXTENT_CSUM 4120596480) itemoff 275 itemsize 300 <<< > range start 4120596480 end 4120903680 length 307200 > leaf 29753344 items 3 free space 1936 generation 19 owner CSUM_TREE > item 0 key (18446744073457893366 EXTENT_CSUM 77594624) itemoff 2323 itemsize 1672 > range start 77594624 end 79306752 length 1712128 > ... > > Note the item 4 key of leaf 29757440, which is obviously too large, and > even larger than the first key of the next leaf. > > However it still follows the key order in that tree block, thus tree > checker is unable to detect it at read time, since tree checker can only > work inside a leaf, thus such complex corruption can't be rejected in > advance. > > [FIX] > The next timing to detect such problem is at tree block merge time, > which is in push_node_left(), balance_node_right(), push_leaf_left() and > push_leaf_right(). > > Now we check if the key order of the right most key of the left node is > larger than the left most key of the right node. > > By this we don't need to call the full tree-check, while still keeps the > key order correct as key order in each node is already checked by tree > checker thus we only need to check the above two slots. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202833 > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>, albeit see below for some minors suggestions (feel free to ignore). > --- > fs/btrfs/ctree.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 63 insertions(+) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index 5df76c17775a..38118e050689 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -3219,6 +3219,52 @@ void btrfs_set_item_key_safe(struct btrfs_fs_info *fs_info, > fixup_low_keys(path, &disk_key, 1); > } > > +/* > + * Check the cross tree block key ordering. > + * > + * Tree-checker only works inside one tree block, thus the following > + * corruption can not be rejected by tree-checker: > + * Leaf @left | Leaf @right > + * -------------------------------------------------------------- > + * | 1 | 2 | 3 | 4 | 5 | f6 | | 7 | 8 | > + * > + * Key f6 in leaf @left itself is valid, but not valid when the next > + * key in leaf @right is 7. > + * This can only be checked at tree block merge time. > + * And since tree checker has ensured all key order in each tree block > + * is correct, we only need to bother the last key of @left and the first > + * key of @right. > + */ > +static int check_cross_tree_key_order(struct extent_buffer *left, > + struct extent_buffer *right) > +{ > + struct btrfs_key left_last; > + struct btrfs_key right_first; > + int level = btrfs_header_level(left); > + int nr_left = btrfs_header_nritems(left); > + int nr_right = btrfs_header_nritems(right); > + > + /* No key to check in one of the tree blocks */ > + if (!nr_left || !nr_right) > + return 0; > + if (level) { > + btrfs_node_key_to_cpu(left, &left_last, nr_left - 1); > + btrfs_node_key_to_cpu(right, &right_first, 0); > + } else { > + btrfs_item_key_to_cpu(left, &left_last, nr_left - 1); > + btrfs_item_key_to_cpu(right, &right_first, 0); > + } > + if (btrfs_comp_cpu_keys(&left_last, &right_first) >= 0) { > + btrfs_crit(left->fs_info, > +"bad key order cross tree blocks, left last (%llu %u %llu) right first (%llu %u %llu", > + left_last.objectid, left_last.type, > + left_last.offset, right_first.objectid, > + right_first.type, right_first.offset); > + return -EUCLEAN; > + } > + return 0; > +} > + nit: I wonder if it will make it a bit easier to reason about the code if that function is renamed to valid_cross_block_key_order and make it return true or false, then it's callers will do if (!valid_cross_block_key_ordered) { return -EUCLEAN } I guess it won't be much different than it is now. > /* > * try to push data from one node into the next node left in the > * tree. > @@ -3263,6 +3309,10 @@ static int push_node_left(struct btrfs_trans_handle *trans, > } else > push_items = min(src_nritems - 8, push_items); > > + /* dst is the left eb src is the middle eb */ nit: missing ',' between 'eb' and 'src'. But this is very minor. > + ret = check_cross_tree_key_order(dst, src); > + if (ret < 0) > + return ret; > ret = tree_mod_log_eb_copy(dst, src, dst_nritems, 0, push_items); > if (ret) { > btrfs_abort_transaction(trans, ret); > @@ -3331,6 +3381,10 @@ static int balance_node_right(struct btrfs_trans_handle *trans, > if (max_push < push_items) > push_items = max_push; > > + /* dst is the right eb, src is the middle eb */ > + ret = check_cross_tree_key_order(src, dst); > + if (ret < 0) > + return ret; > ret = tree_mod_log_insert_move(dst, push_items, 0, dst_nritems); > BUG_ON(ret < 0); > memmove_extent_buffer(dst, btrfs_node_key_ptr_offset(push_items), > @@ -3810,6 +3864,12 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root > if (left_nritems == 0) > goto out_unlock; > > + ret = check_cross_tree_key_order(left, right); > + if (ret < 0) { > + btrfs_tree_unlock(right); > + free_extent_buffer(right); > + return ret; > + } > if (path->slots[0] == left_nritems && !empty) { > /* Key greater than all keys in the leaf, right neighbor has > * enough room for it and we're not emptying our leaf to delete > @@ -4048,6 +4108,9 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root > goto out; > } > > + ret = check_cross_tree_key_order(left, right); > + if (ret < 0) > + goto out; > return __push_leaf_left(path, min_data_size, > empty, left, free_space, right_nritems, > max_slot); >
