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* [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock
@ 2022-12-16 15:50 Chao Yu
  2022-12-16 20:42 ` Eric Biggers
  0 siblings, 1 reply; 17+ messages in thread
From: Chao Yu @ 2022-12-16 15:50 UTC (permalink / raw)
  To: jaegeuk; +Cc: syzbot+4793f6096d174c90b4f7, linux-kernel, linux-f2fs-devel

There is a potential deadlock reported by syzbot as below:

F2FS-fs (loop2): invalid crc value
F2FS-fs (loop2): Found nat_bits in checkpoint
F2FS-fs (loop2): Mounted with checkpoint version = 48b305e4
======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc8-syzkaller-33330-ga5541c0811a0 #0 Not tainted
------------------------------------------------------
syz-executor.2/32123 is trying to acquire lock:
ffff0000c0e1a608 (&mm->mmap_lock){++++}-{3:3}, at: __might_fault+0x54/0xb4 mm/memory.c:5644

but task is already holding lock:
ffff0001317c6088 (&sbi->sb_lock){++++}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2205 [inline]
ffff0001317c6088 (&sbi->sb_lock){++++}-{3:3}, at: f2fs_ioc_get_encryption_pwsalt fs/f2fs/file.c:2334 [inline]
ffff0001317c6088 (&sbi->sb_lock){++++}-{3:3}, at: __f2fs_ioctl+0x1370/0x3318 fs/f2fs/file.c:4151

which lock already depends on the new lock.

Chain exists of:
  &mm->mmap_lock --> &nm_i->nat_tree_lock --> &sbi->sb_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->sb_lock);
                               lock(&nm_i->nat_tree_lock);
                               lock(&sbi->sb_lock);
  lock(&mm->mmap_lock);

Let's try to avoid above deadlock condition by moving __might_fault()
out of sbi->sb_lock coverage.

Fixes: 95fa90c9e5a7 ("f2fs: support recording errors into superblock")
Link: https://lore.kernel.org/linux-f2fs-devel/000000000000cd5fe305ef617fe2@google.com/T/#u
Reported-by: syzbot+4793f6096d174c90b4f7@syzkaller.appspotmail.com
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/file.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index cad4bdd6f097..4bc98dbe8292 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2336,6 +2336,7 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	u8 encrypt_pw_salt[16];
 	int err;
 
 	if (!f2fs_sb_has_encrypt(sbi))
@@ -2360,12 +2361,14 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 		goto out_err;
 	}
 got_it:
-	if (copy_to_user((__u8 __user *)arg, sbi->raw_super->encrypt_pw_salt,
-									16))
-		err = -EFAULT;
+	memcpy(encrypt_pw_salt, sbi->raw_super->encrypt_pw_salt, 16);
 out_err:
 	f2fs_up_write(&sbi->sb_lock);
 	mnt_drop_write_file(filp);
+
+	if (!err && copy_to_user((__u8 __user *)arg, encrypt_pw_salt, 16))
+		err = -EFAULT;
+
 	return err;
 }
 
-- 
2.36.1



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^ permalink raw reply related	[flat|nested] 17+ messages in thread
* [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock
@ 2025-10-14 11:47 Chao Yu via Linux-f2fs-devel
  0 siblings, 0 replies; 17+ messages in thread
From: Chao Yu via Linux-f2fs-devel @ 2025-10-14 11:47 UTC (permalink / raw)
  To: jaegeuk
  Cc: syzbot+14b90e1156b9f6fc1266, linux-kernel, linux-f2fs-devel,
	Jiaming Zhang, stable

As Jiaming Zhang and syzbot reported, there is potential deadlock in
f2fs as below:

Chain exists of:
  &sbi->cp_rwsem --> fs_reclaim --> sb_internal#2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_internal#2);
                               lock(fs_reclaim);
                               lock(sb_internal#2);
  rlock(&sbi->cp_rwsem);

 *** DEADLOCK ***

3 locks held by kswapd0/73:
 #0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:7015 [inline]
 #0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/vmscan.c:7389
 #1: ffff8880118400e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff8880118400e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_cache_scan+0x91/0x4b0 fs/super.c:197
 #2: ffff888011840610 (sb_internal#2){.+.+}-{0:0}, at: f2fs_evict_inode+0x8d9/0x1b60 fs/f2fs/inode.c:890

stack backtrace:
CPU: 0 UID: 0 PID: 73 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 down_read+0x46/0x2e0 kernel/locking/rwsem.c:1537
 f2fs_down_read fs/f2fs/f2fs.h:2278 [inline]
 f2fs_lock_op fs/f2fs/f2fs.h:2357 [inline]
 f2fs_do_truncate_blocks+0x21c/0x10c0 fs/f2fs/file.c:791
 f2fs_truncate_blocks+0x10a/0x300 fs/f2fs/file.c:867
 f2fs_truncate+0x489/0x7c0 fs/f2fs/file.c:925
 f2fs_evict_inode+0x9f2/0x1b60 fs/f2fs/inode.c:897
 evict+0x504/0x9c0 fs/inode.c:810
 f2fs_evict_inode+0x1dc/0x1b60 fs/f2fs/inode.c:853
 evict+0x504/0x9c0 fs/inode.c:810
 dispose_list fs/inode.c:852 [inline]
 prune_icache_sb+0x21b/0x2c0 fs/inode.c:1000
 super_cache_scan+0x39b/0x4b0 fs/super.c:224
 do_shrink_slab+0x6ef/0x1110 mm/shrinker.c:437
 shrink_slab_memcg mm/shrinker.c:550 [inline]
 shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
 shrink_one+0x28a/0x7c0 mm/vmscan.c:4955
 shrink_many mm/vmscan.c:5016 [inline]
 lru_gen_shrink_node mm/vmscan.c:5094 [inline]
 shrink_node+0x315d/0x3780 mm/vmscan.c:6081
 kswapd_shrink_node mm/vmscan.c:6941 [inline]
 balance_pgdat mm/vmscan.c:7124 [inline]
 kswapd+0x147c/0x2800 mm/vmscan.c:7389
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

The root cause is deadlock among four locks as below:

kswapd
- fs_reclaim				--- Lock A
 - shrink_one
  - evict
   - f2fs_evict_inode
    - sb_start_intwrite			--- Lock B

- iput
 - evict
  - f2fs_evict_inode
   - sb_start_intwrite			--- Lock B
   - f2fs_truncate
    - f2fs_truncate_blocks
     - f2fs_do_truncate_blocks
      - f2fs_lock_op			--- Lock C

ioctl
- f2fs_ioc_commit_atomic_write
 - f2fs_lock_op				--- Lock C
  - __f2fs_commit_atomic_write
   - __replace_atomic_write_block
    - f2fs_get_dnode_of_data
     - __get_node_folio
      - f2fs_check_nid_range
       - f2fs_handle_error
        - f2fs_record_errors
         - f2fs_down_write		--- Lock D

open
- do_open
 - do_truncate
  - security_inode_need_killpriv
   - f2fs_getxattr
    - lookup_all_xattrs
     - f2fs_handle_error
      - f2fs_record_errors
       - f2fs_down_write		--- Lock D
        - f2fs_commit_super
         - read_mapping_folio
          - filemap_alloc_folio_noprof
           - prepare_alloc_pages
            - fs_reclaim_acquire	--- Lock A

In order to avoid such deadlock, we need to avoid grabbing sb_lock in
f2fs_handle_error(), so, let's use asynchronous method instead:
- remove f2fs_handle_error() implementation
- rename f2fs_handle_error_async() to f2fs_handle_error()
- spread f2fs_handle_error()

Fixes: 95fa90c9e5a7 ("f2fs: support recording errors into superblock")
Cc: stable@kernel.org
Reported-by: syzbot+14b90e1156b9f6fc1266@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-f2fs-devel/68eae49b.050a0220.ac43.0001.GAE@google.com
Reported-by: Jiaming Zhang <r772577952@gmail.com>
Closes: https://lore.kernel.org/lkml/CANypQFa-Gy9sD-N35o3PC+FystOWkNuN8pv6S75HLT0ga-Tzgw@mail.gmail.com
Signed-off-by: Chao Yu <chao@kernel.org>
---
Please notice that this patch is base on below patch:
f2fs: fix to do sanity check on node footer in {read,write}_end_io

 fs/f2fs/compress.c |  5 +----
 fs/f2fs/f2fs.h     |  1 -
 fs/f2fs/node.c     |  6 ++----
 fs/f2fs/super.c    | 41 -----------------------------------------
 4 files changed, 3 insertions(+), 50 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 6ad8d3bc6df7..811bfe38e5c0 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -759,10 +759,7 @@ void f2fs_decompress_cluster(struct decompress_io_ctx *dic, bool in_task)
 		ret = -EFSCORRUPTED;
 
 		/* Avoid f2fs_commit_super in irq context */
-		if (!in_task)
-			f2fs_handle_error_async(sbi, ERROR_FAIL_DECOMPRESSION);
-		else
-			f2fs_handle_error(sbi, ERROR_FAIL_DECOMPRESSION);
+		f2fs_handle_error(sbi, ERROR_FAIL_DECOMPRESSION);
 		goto out_release;
 	}
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c589aed069d9..c3e968787d7e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3815,7 +3815,6 @@ void f2fs_quota_off_umount(struct super_block *sb);
 void f2fs_save_errors(struct f2fs_sb_info *sbi, unsigned char flag);
 void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason);
 void f2fs_handle_error(struct f2fs_sb_info *sbi, unsigned char error);
-void f2fs_handle_error_async(struct f2fs_sb_info *sbi, unsigned char error);
 int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover);
 int f2fs_sync_fs(struct super_block *sb, int sync);
 int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index e70c970a3047..ce471e033774 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1550,10 +1550,8 @@ int f2fs_sanity_check_node_footer(struct f2fs_sb_info *sbi,
 		ntype, nid, nid_of_node(folio), ino_of_node(folio),
 		ofs_of_node(folio), cpver_of_node(folio),
 		next_blkaddr_of_node(folio));
-	if (in_irq)
-		f2fs_handle_error_async(sbi, ERROR_INCONSISTENT_FOOTER);
-	else
-		f2fs_handle_error(sbi, ERROR_INCONSISTENT_FOOTER);
+
+	f2fs_handle_error(sbi, ERROR_INCONSISTENT_FOOTER);
 	return -EFSCORRUPTED;
 }
 
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 2ae341768a39..1dd4a93ba4bb 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4544,48 +4544,7 @@ void f2fs_save_errors(struct f2fs_sb_info *sbi, unsigned char flag)
 	spin_unlock_irqrestore(&sbi->error_lock, flags);
 }
 
-static bool f2fs_update_errors(struct f2fs_sb_info *sbi)
-{
-	unsigned long flags;
-	bool need_update = false;
-
-	spin_lock_irqsave(&sbi->error_lock, flags);
-	if (sbi->error_dirty) {
-		memcpy(F2FS_RAW_SUPER(sbi)->s_errors, sbi->errors,
-							MAX_F2FS_ERRORS);
-		sbi->error_dirty = false;
-		need_update = true;
-	}
-	spin_unlock_irqrestore(&sbi->error_lock, flags);
-
-	return need_update;
-}
-
-static void f2fs_record_errors(struct f2fs_sb_info *sbi, unsigned char error)
-{
-	int err;
-
-	f2fs_down_write(&sbi->sb_lock);
-
-	if (!f2fs_update_errors(sbi))
-		goto out_unlock;
-
-	err = f2fs_commit_super(sbi, false);
-	if (err)
-		f2fs_err_ratelimited(sbi,
-			"f2fs_commit_super fails to record errors:%u, err:%d",
-			error, err);
-out_unlock:
-	f2fs_up_write(&sbi->sb_lock);
-}
-
 void f2fs_handle_error(struct f2fs_sb_info *sbi, unsigned char error)
-{
-	f2fs_save_errors(sbi, error);
-	f2fs_record_errors(sbi, error);
-}
-
-void f2fs_handle_error_async(struct f2fs_sb_info *sbi, unsigned char error)
 {
 	f2fs_save_errors(sbi, error);
 
-- 
2.49.0



_______________________________________________
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https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply related	[flat|nested] 17+ messages in thread
* [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock
@ 2022-01-27  5:44 Chao Yu
  2022-01-27 21:59 ` Jaegeuk Kim
  0 siblings, 1 reply; 17+ messages in thread
From: Chao Yu @ 2022-01-27  5:44 UTC (permalink / raw)
  To: jaegeuk; +Cc: Zhiguo Niu, Jing Xia, linux-kernel, linux-f2fs-devel

Quoted from Jing Xia's report, there is a potential deadlock may happen
between kworker and checkpoint as below:

[T:writeback]				[T:checkpoint]
- wb_writeback
 - blk_start_plug
bio contains NodeA was plugged in writeback threads
					- do_writepages  -- sync write inodeB, inc wb_sync_req[DATA]
					 - f2fs_write_data_pages
					  - f2fs_write_single_data_page -- write last dirty page
					   - f2fs_do_write_data_page
					    - set_page_writeback  -- clear page dirty flag and
					    PAGECACHE_TAG_DIRTY tag in radix tree
					    - f2fs_outplace_write_data
					     - f2fs_update_data_blkaddr
					      - f2fs_wait_on_page_writeback -- wait NodeA to writeback here
					   - inode_dec_dirty_pages
 - writeback_sb_inodes
  - writeback_single_inode
   - do_writepages
    - f2fs_write_data_pages -- skip writepages due to wb_sync_req[DATA]
     - wbc->pages_skipped += get_dirty_pages() -- PAGECACHE_TAG_DIRTY is not set but get_dirty_pages() returns one
  - requeue_inode -- requeue inode to wb->b_dirty queue due to non-zero.pages_skipped
 - blk_finish_plug

Let's try to avoid deadlock condition by forcing unplugging previous bio via
blk_finish_plug(current->plug) once we'v skipped writeback in writepages()
due to valid sbi->wb_sync_req[DATA/NODE].

Fixes: 687de7f1010c ("f2fs: avoid IO split due to mixed WB_SYNC_ALL and WB_SYNC_NONE")
Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Signed-off-by: Jing Xia <jing.xia@unisoc.com>
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/data.c | 6 +++++-
 fs/f2fs/node.c | 6 +++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 76d6fe7b0c8f..932a4c81acaf 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3174,8 +3174,12 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
 	/* to avoid spliting IOs due to mixed WB_SYNC_ALL and WB_SYNC_NONE */
 	if (wbc->sync_mode == WB_SYNC_ALL)
 		atomic_inc(&sbi->wb_sync_req[DATA]);
-	else if (atomic_read(&sbi->wb_sync_req[DATA]))
+	else if (atomic_read(&sbi->wb_sync_req[DATA])) {
+		/* to avoid potential deadlock */
+		if (current->plug)
+			blk_finish_plug(current->plug);
 		goto skip_write;
+	}
 
 	if (__should_serialize_io(inode, wbc)) {
 		mutex_lock(&sbi->writepages);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 556fcd8457f3..69c6bcaf5aae 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -2106,8 +2106,12 @@ static int f2fs_write_node_pages(struct address_space *mapping,
 
 	if (wbc->sync_mode == WB_SYNC_ALL)
 		atomic_inc(&sbi->wb_sync_req[NODE]);
-	else if (atomic_read(&sbi->wb_sync_req[NODE]))
+	else if (atomic_read(&sbi->wb_sync_req[NODE])) {
+		/* to avoid potential deadlock */
+		if (current->plug)
+			blk_finish_plug(current->plug);
 		goto skip_write;
+	}
 
 	trace_f2fs_writepages(mapping->host, wbc, NODE);
 
-- 
2.32.0



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^ permalink raw reply related	[flat|nested] 17+ messages in thread
end of thread, other threads:[~2025-10-14 11:47 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-12-16 15:50 [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock Chao Yu
2022-12-16 20:42 ` Eric Biggers
  -- strict thread matches above, loose matches on Subject: below --
2025-10-14 11:47 Chao Yu via Linux-f2fs-devel
2022-01-27  5:44 Chao Yu
2022-01-27 21:59 ` Jaegeuk Kim
2022-01-28  1:43   ` Chao Yu
2022-01-29  0:37     ` Jaegeuk Kim
2022-01-29  1:48       ` Chao Yu
2022-02-03  1:51         ` Jaegeuk Kim
2022-02-03 14:57           ` Chao Yu
2022-02-25  3:02             ` Chao Yu
2022-03-02  3:32               ` Chao Yu
2022-03-02  5:26                 ` Jaegeuk Kim
2022-03-02  8:14                   ` Chao Yu
2022-03-02 19:45                     ` Jaegeuk Kim
2022-03-03  2:32                       ` Chao Yu
2022-03-03 21:30                         ` Jaegeuk Kim

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