[PATCH] ntfs3: fix deadlock in mark_as_free_ex

[Lizhi Xu]

syzbot reported a deadlock in mark_as_free_ex. [1]

Reset the order of mft and used locks to avoid this issue.

[1]
WARNING: possible circular locking dependency detected
6.13.0-rc2-syzkaller-00036-g231825b2e1ff #0 Not tainted
------------------------------------------------------
syz-executor149/6544 is trying to acquire lock:
ffff88807e17a270 (&wnd->rw_lock){++++}-{4:4}, at: mark_as_free_ex+0x3e/0x390 fs/ntfs3/fsntfs.c:2484

but task is already holding lock:
ffff8880705e43c8 (&ni->file.run_lock#2){++++}-{4:4}, at: ntfs_truncate fs/ntfs3/file.c:505 [inline]
ffff8880705e43c8 (&ni->file.run_lock#2){++++}-{4:4}, at: ntfs_setattr+0x6d3/0xb80 fs/ntfs3/file.c:824

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ni->file.run_lock#2){++++}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524
       run_unpack_ex+0x55e/0x9e0 fs/ntfs3/run.c:1119
       ntfs_read_mft fs/ntfs3/inode.c:401 [inline]
       ntfs_iget5+0x1f9a/0x37b0 fs/ntfs3/inode.c:537
       ntfs_dir_emit fs/ntfs3/dir.c:335 [inline]
       ntfs_read_hdr+0x700/0xb80 fs/ntfs3/dir.c:383
       ntfs_readdir+0x91f/0xf00 fs/ntfs3/dir.c:494
       iterate_dir+0x571/0x800 fs/readdir.c:108
       __do_sys_getdents64 fs/readdir.c:403 [inline]
       __se_sys_getdents64+0x1e2/0x4b0 fs/readdir.c:389
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&wnd->rw_lock){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       down_write_nested+0xa2/0x220 kernel/locking/rwsem.c:1693
       mark_as_free_ex+0x3e/0x390 fs/ntfs3/fsntfs.c:2484
       run_deallocate_ex+0x244/0x5f0 fs/ntfs3/attrib.c:122
       attr_set_size+0x168d/0x4300 fs/ntfs3/attrib.c:753
       ntfs_truncate fs/ntfs3/file.c:506 [inline]
       ntfs_setattr+0x7a4/0xb80 fs/ntfs3/file.c:824
       notify_change+0xbca/0xe90 fs/attr.c:552
       do_truncate+0x220/0x310 fs/open.c:65
       handle_truncate fs/namei.c:3449 [inline]
       do_open fs/namei.c:3832 [inline]
       path_openat+0x2e1e/0x3590 fs/namei.c:3987
       do_filp_open+0x27f/0x4e0 fs/namei.c:4014
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1402
       do_sys_open fs/open.c:1417 [inline]
       __do_sys_open fs/open.c:1425 [inline]
       __se_sys_open fs/open.c:1421 [inline]
       __x64_sys_open+0x225/0x270 fs/open.c:1421
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ni->file.run_lock#2);
                               lock(&wnd->rw_lock);
                               lock(&ni->file.run_lock#2);
  lock(&wnd->rw_lock);

 *** DEADLOCK ***

Fixes: 5fc982fe7eca ("fs/ntfs3: Fix case when unmarked clusters intersect with zone")
Reported-by: syzbot+8df514c431bd240c5644@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=8df514c431bd240c5644
Tested-by: syzbot+8df514c431bd240c5644@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
 fs/ntfs3/run.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/ntfs3/run.c b/fs/ntfs3/run.c
index 6e86d66197ef..fdac1f941379 100644
--- a/fs/ntfs3/run.c
+++ b/fs/ntfs3/run.c
@@ -1096,9 +1096,17 @@ int run_unpack_ex(struct runs_tree *run, struct ntfs_sb_info *sbi, CLST ino,
 
 		/* Looks like volume is corrupted. */
 		ntfs_set_state(sbi, NTFS_DIRTY_ERROR);
-
-		if (!down_write_trylock(&wnd->rw_lock))
+		struct rw_semaphore *lock =
+			is_mounted(sbi) ? &sbi->mft.ni->file.run_lock :
+					  NULL;
+		if (zone && lock)
+			down_read(lock);
+
+		if (!down_write_trylock(&wnd->rw_lock)) {
+			if (zone && lock)
+				up_read(lock);
 			continue;
+		}
 
 		if (zone) {
 			/*
@@ -1112,16 +1120,12 @@ int run_unpack_ex(struct runs_tree *run, struct ntfs_sb_info *sbi, CLST ino,
 		err = wnd_set_used_safe(wnd, lcn, len, &done);
 		if (zone) {
 			/* Restore zone. Lock mft run. */
-			struct rw_semaphore *lock =
-				is_mounted(sbi) ? &sbi->mft.ni->file.run_lock :
-						  NULL;
-			if (lock)
-				down_read(lock);
 			ntfs_refresh_zone(sbi);
-			if (lock)
-				up_read(lock);
 		}
 		up_write(&wnd->rw_lock);
+		if (zone && lock)
+			up_read(lock);
+
 		if (err)
 			return err;
 	}
-- 
2.43.0