From: Filipe Manana fdmanana@suse.com

stable inclusion from stable-v5.12.5 commit 96157707c0420e3d3edfe046f1cc797fee117ade bugzilla: https://gitee.com/src-openeuler/kernel/issues/I94K22 CVE: CVE-2021-46987

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

---------------------------

[ Upstream commit f9baa501b4fd6962257853d46ddffbc21f27e344 ]

There are a few exceptional cases where cloning an inline extent needs to copy the inline extent data into a page of the destination inode.

When this happens, we end up starting a transaction while having a dirty page for the destination inode and while having the range locked in the destination's inode iotree too. Because when reserving metadata space for a transaction we may need to flush existing delalloc in case there is not enough free space, we have a mechanism in place to prevent a deadlock, which was introduced in commit 3d45f221ce627d ("btrfs: fix deadlock when cloning inline extent and low on free metadata space").

However when using qgroups, a transaction also reserves metadata qgroup space, which can also result in flushing delalloc in case there is not enough available space at the moment. When this happens we deadlock, since flushing delalloc requires locking the file range in the inode's iotree and the range was already locked at the very beginning of the clone operation, before attempting to start the transaction.

When this issue happens, stack traces like the following are reported:

[72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000 [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142) [72747.556271] Call Trace: [72747.556273] __schedule+0x296/0x760 [72747.556277] schedule+0x3c/0xa0 [72747.556279] io_schedule+0x12/0x40 [72747.556284] __lock_page+0x13c/0x280 [72747.556287] ? generic_file_readonly_mmap+0x70/0x70 [72747.556325] extent_write_cache_pages+0x22a/0x440 [btrfs] [72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160 [72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs] [72747.556362] ? update_group_capacity+0x25/0x210 [72747.556366] ? cpumask_next_and+0x1a/0x20 [72747.556391] extent_writepages+0x44/0xa0 [btrfs] [72747.556394] do_writepages+0x41/0xd0 [72747.556398] __writeback_single_inode+0x39/0x2a0 [72747.556403] writeback_sb_inodes+0x1ea/0x440 [72747.556407] __writeback_inodes_wb+0x5f/0xc0 [72747.556410] wb_writeback+0x235/0x2b0 [72747.556414] ? get_nr_inodes+0x35/0x50 [72747.556417] wb_workfn+0x354/0x490 [72747.556420] ? newidle_balance+0x2c5/0x3e0 [72747.556424] process_one_work+0x1aa/0x340 [72747.556426] worker_thread+0x30/0x390 [72747.556429] ? create_worker+0x1a0/0x1a0 [72747.556432] kthread+0x116/0x130 [72747.556435] ? kthread_park+0x80/0x80 [72747.556438] ret_from_fork+0x1f/0x30

[72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs] [72747.566961] Call Trace: [72747.566964] __schedule+0x296/0x760 [72747.566968] ? finish_wait+0x80/0x80 [72747.566970] schedule+0x3c/0xa0 [72747.566995] wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs] [72747.566999] ? finish_wait+0x80/0x80 [72747.567024] lock_extent_bits+0x37/0x90 [btrfs] [72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs] [72747.567051] ? find_get_pages_range_tag+0x2cd/0x380 [72747.567076] __extent_writepage+0x203/0x320 [btrfs] [72747.567102] extent_write_cache_pages+0x2bb/0x440 [btrfs] [72747.567106] ? update_load_avg+0x7e/0x5f0 [72747.567109] ? enqueue_entity+0xf4/0x6f0 [72747.567134] extent_writepages+0x44/0xa0 [btrfs] [72747.567137] ? enqueue_task_fair+0x93/0x6f0 [72747.567140] do_writepages+0x41/0xd0 [72747.567144] __filemap_fdatawrite_range+0xc7/0x100 [72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs] [72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs] [72747.567200] process_one_work+0x1aa/0x340 [72747.567202] worker_thread+0x30/0x390 [72747.567205] ? create_worker+0x1a0/0x1a0 [72747.567208] kthread+0x116/0x130 [72747.567211] ? kthread_park+0x80/0x80 [72747.567214] ret_from_fork+0x1f/0x30

[72747.569686] task:fsstress state:D stack: 0 pid:841421 ppid:841417 flags:0x00000000 [72747.569689] Call Trace: [72747.569691] __schedule+0x296/0x760 [72747.569694] schedule+0x3c/0xa0 [72747.569721] try_flush_qgroup+0x95/0x140 [btrfs] [72747.569725] ? finish_wait+0x80/0x80 [72747.569753] btrfs_qgroup_reserve_data+0x34/0x50 [btrfs] [72747.569781] btrfs_check_data_free_space+0x5f/0xa0 [btrfs] [72747.569804] btrfs_buffered_write+0x1f7/0x7f0 [btrfs] [72747.569810] ? path_lookupat.isra.48+0x97/0x140 [72747.569833] btrfs_file_write_iter+0x81/0x410 [btrfs] [72747.569836] ? __kmalloc+0x16a/0x2c0 [72747.569839] do_iter_readv_writev+0x160/0x1c0 [72747.569843] do_iter_write+0x80/0x1b0 [72747.569847] vfs_writev+0x84/0x140 [72747.569869] ? btrfs_file_llseek+0x38/0x270 [btrfs] [72747.569873] do_writev+0x65/0x100 [72747.569876] do_syscall_64+0x33/0x40 [72747.569879] entry_SYSCALL_64_after_hwframe+0x44/0xa9

[72747.569899] task:fsstress state:D stack: 0 pid:841424 ppid:841417 flags:0x00004000 [72747.569903] Call Trace: [72747.569906] __schedule+0x296/0x760 [72747.569909] schedule+0x3c/0xa0 [72747.569936] try_flush_qgroup+0x95/0x140 [btrfs] [72747.569940] ? finish_wait+0x80/0x80 [72747.569967] __btrfs_qgroup_reserve_meta+0x36/0x50 [btrfs] [72747.569989] start_transaction+0x279/0x580 [btrfs] [72747.570014] clone_copy_inline_extent+0x332/0x490 [btrfs] [72747.570041] btrfs_clone+0x5b7/0x7a0 [btrfs] [72747.570068] ? lock_extent_bits+0x64/0x90 [btrfs] [72747.570095] btrfs_clone_files+0xfc/0x150 [btrfs] [72747.570122] btrfs_remap_file_range+0x3d8/0x4a0 [btrfs] [72747.570126] do_clone_file_range+0xed/0x200 [72747.570131] vfs_clone_file_range+0x37/0x110 [72747.570134] ioctl_file_clone+0x7d/0xb0 [72747.570137] do_vfs_ioctl+0x138/0x630 [72747.570140] __x64_sys_ioctl+0x62/0xc0 [72747.570143] do_syscall_64+0x33/0x40 [72747.570146] entry_SYSCALL_64_after_hwframe+0x44/0xa9

So fix this by skipping the flush of delalloc for an inode that is flagged with BTRFS_INODE_NO_DELALLOC_FLUSH, meaning it is currently under such a special case of cloning an inline extent, when flushing delalloc during qgroup metadata reservation.

The special cases for cloning inline extents were added in kernel 5.7 by by commit 05a5a7621ce66c ("Btrfs: implement full reflink support for inline extents"), while having qgroup metadata space reservation flushing delalloc when low on space was added in kernel 5.9 by commit c53e9653605dbf ("btrfs: qgroup: try to flush qgroup space when we get -EDQUOT"). So use a "Fixes:" tag for the later commit to ease stable kernel backports.

Reported-by: Wang Yugui wangyugui@e16-tech.com Link: https://lore.kernel.org/linux-btrfs/20210421083137.31E3.409509F4@e16-tech.co... Fixes: c53e9653605dbf ("btrfs: qgroup: try to flush qgroup space when we get -EDQUOT") CC: stable@vger.kernel.org # 5.9+ Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Yifan Qiao qiaoyifan4@huawei.com --- fs/btrfs/ctree.h | 2 +- fs/btrfs/inode.c | 4 ++-- fs/btrfs/ioctl.c | 2 +- fs/btrfs/qgroup.c | 2 +- fs/btrfs/send.c | 4 ++-- fs/btrfs/transaction.c | 2 +- 6 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index bcc6848bb6d6..92ecb4562584 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3008,7 +3008,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans, struct inode *inode, u64 new_size, u32 min_type);

-int btrfs_start_delalloc_snapshot(struct btrfs_root *root); +int btrfs_start_delalloc_snapshot(struct btrfs_root *root, bool in_reclaim_context); int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr, bool in_reclaim_context); int btrfs_set_extent_delalloc(struct btrfs_inode *inode, u64 start, u64 end, diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index c900a39666e3..d87a53613e34 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -9526,7 +9526,7 @@ static int start_delalloc_inodes(struct btrfs_root *root, return ret; }

-int btrfs_start_delalloc_snapshot(struct btrfs_root *root) +int btrfs_start_delalloc_snapshot(struct btrfs_root *root, bool in_reclaim_context) { struct writeback_control wbc = { .nr_to_write = LONG_MAX, @@ -9539,7 +9539,7 @@ int btrfs_start_delalloc_snapshot(struct btrfs_root *root) if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) return -EROFS;

- return start_delalloc_inodes(root, &wbc, true, false); + return start_delalloc_inodes(root, &wbc, true, in_reclaim_context); }

int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr, diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 63bf68e0b006..e71c80b45bb1 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1030,7 +1030,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, */ btrfs_drew_read_lock(&root->snapshot_lock);

- ret = btrfs_start_delalloc_snapshot(root); + ret = btrfs_start_delalloc_snapshot(root, false); if (ret) goto out;

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index a67323c2d41f..506d12ef0d16 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -3695,7 +3695,7 @@ static int try_flush_qgroup(struct btrfs_root *root) return 0; }

- ret = btrfs_start_delalloc_snapshot(root); + ret = btrfs_start_delalloc_snapshot(root, true); if (ret < 0) goto out; btrfs_wait_ordered_extents(root, U64_MAX, 0, (u64)-1); diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index b081b61e97c8..ff3114e652b3 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -7196,7 +7196,7 @@ static int flush_delalloc_roots(struct send_ctx *sctx) int i;

if (root) { - ret = btrfs_start_delalloc_snapshot(root); + ret = btrfs_start_delalloc_snapshot(root, false); if (ret) return ret; btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX); @@ -7204,7 +7204,7 @@ static int flush_delalloc_roots(struct send_ctx *sctx)

for (i = 0; i < sctx->clone_roots_cnt; i++) { root = sctx->clone_roots[i].root; - ret = btrfs_start_delalloc_snapshot(root); + ret = btrfs_start_delalloc_snapshot(root, false); if (ret) return ret; btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX); diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index abd67f984fbc..6b1bdb710123 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -2044,7 +2044,7 @@ static inline int btrfs_start_delalloc_flush(struct btrfs_trans_handle *trans) list_for_each_entry(pending, head, list) { int ret;

- ret = btrfs_start_delalloc_snapshot(pending->root); + ret = btrfs_start_delalloc_snapshot(pending->root, false); if (ret) return ret; }