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possible deadlock in ovl_copy_up_flags (2)

Status: upstream: reported on 2026/05/29 09:34
Subsystems: overlayfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+b754bc5f4c7fddac5253@syzkaller.appspotmail.com
First crash: 39d, last: 8d05h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
db2d8686-c50d-4d29-9ced-38ae56a4a672 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ possible deadlock in ovl_copy_up_flags (2) 2026/06/02 16:09 2026/06/02 16:09 2026/06/02 16:14 62fe15281f5011cd203d8845b8767b10e7443aa5

			
		
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [overlayfs?] possible deadlock in ovl_copy_up_flags (2) 0 (1) 2026/05/29 09:34
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in ovl_copy_up_flags overlayfs 4 C done 7 750d 771d 26/29 fixed on 2024/07/09 19:14

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.232/5803 is trying to acquire lock:
ffff0000cff12410 (sb_writers#3){.+.+}-{0:0}, at: ovl_copy_up_tmpfile fs/overlayfs/copy_up.c:864 [inline]
ffff0000cff12410 (sb_writers#3){.+.+}-{0:0}, at: ovl_do_copy_up fs/overlayfs/copy_up.c:986 [inline]
ffff0000cff12410 (sb_writers#3){.+.+}-{0:0}, at: ovl_copy_up_one fs/overlayfs/copy_up.c:1189 [inline]
ffff0000cff12410 (sb_writers#3){.+.+}-{0:0}, at: ovl_copy_up_flags+0xc58/0x28c0 fs/overlayfs/copy_up.c:1243

but task is already holding lock:
ffff0000f2dd0a48 (&ovl_i_lock_key[depth]){+.+.}-{4:4}, at: ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:705 [inline]
ffff0000f2dd0a48 (&ovl_i_lock_key[depth]){+.+.}-{4:4}, at: ovl_copy_up_start+0x58/0x264 fs/overlayfs/util.c:735

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&ovl_i_lock_key[depth]){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x164/0xed0 kernel/locking/mutex.c:820
       mutex_lock_interruptible_nested+0x24/0x30 kernel/locking/mutex.c:898
       ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:705 [inline]
       ovl_copy_up_start+0x58/0x264 fs/overlayfs/util.c:735
       ovl_copy_up_one fs/overlayfs/copy_up.c:1182 [inline]
       ovl_copy_up_flags+0x770/0x28c0 fs/overlayfs/copy_up.c:1243
       ovl_copy_up+0x24/0x34 fs/overlayfs/copy_up.c:1282
       ovl_nlink_start+0x8c/0x350 fs/overlayfs/util.c:1168
       ovl_rename_start fs/overlayfs/dir.c:1189 [inline]
       ovl_rename+0x3b0/0xf80 fs/overlayfs/dir.c:1363
       vfs_rename+0xa78/0xd48 fs/namei.c:6064
       filename_renameat2+0x660/0x72c fs/namei.c:6182
       __do_sys_renameat2 fs/namei.c:6211 [inline]
       __se_sys_renameat2 fs/namei.c:6206 [inline]
       __arm64_sys_renameat2+0xec/0x11c fs/namei.c:6206
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
       do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
       el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
       el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594

-> #1 (&ovl_i_mutex_key[depth]/4){+.+.}-{4:4}:
       __lock_release kernel/locking/lockdep.c:5574 [inline]
       lock_release+0x178/0x3b0 kernel/locking/lockdep.c:5889
       up_write+0x38/0x5cc kernel/locking/rwsem.c:1681
       inode_unlock include/linux/fs.h:1039 [inline]
       unlock_two_nondirectories+0x60/0x118 fs/inode.c:1269
       ext4_move_extents+0x3e4/0x3324 fs/ext4/move_extent.c:656
       __ext4_ioctl fs/ext4/ioctl.c:1657 [inline]
       ext4_ioctl+0x2a10/0x4280 fs/ext4/ioctl.c:1922
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:583
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
       do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
       el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
       el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594

-> #0 (sb_writers#3){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x17c0/0x2ebc kernel/locking/lockdep.c:5237
       lock_acquire+0x140/0x364 kernel/locking/lockdep.c:5868
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
       __sb_start_write include/linux/fs/super.h:19 [inline]
       sb_start_write include/linux/fs/super.h:125 [inline]
       ovl_start_write+0xf0/0x324 fs/overlayfs/util.c:32
       ovl_copy_up_tmpfile fs/overlayfs/copy_up.c:864 [inline]
       ovl_do_copy_up fs/overlayfs/copy_up.c:986 [inline]
       ovl_copy_up_one fs/overlayfs/copy_up.c:1189 [inline]
       ovl_copy_up_flags+0xc58/0x28c0 fs/overlayfs/copy_up.c:1243
       ovl_copy_up+0x24/0x34 fs/overlayfs/copy_up.c:1282
       ovl_nlink_start+0x8c/0x350 fs/overlayfs/util.c:1168
       ovl_rename_start fs/overlayfs/dir.c:1189 [inline]
       ovl_rename+0x3b0/0xf80 fs/overlayfs/dir.c:1363
       vfs_rename+0xa78/0xd48 fs/namei.c:6064
       filename_renameat2+0x660/0x72c fs/namei.c:6182
       __do_sys_renameat2 fs/namei.c:6211 [inline]
       __se_sys_renameat2 fs/namei.c:6206 [inline]
       __arm64_sys_renameat2+0xec/0x11c fs/namei.c:6206
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
       do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
       el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
       el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594

other info that might help us debug this:

Chain exists of:
  sb_writers#3 --> &ovl_i_mutex_key[depth]/4 --> &ovl_i_lock_key[depth]

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ovl_i_lock_key[depth]);
                               lock(&ovl_i_mutex_key[depth]/4);
                               lock(&ovl_i_lock_key[depth]);
  rlock(sb_writers#3);

 *** DEADLOCK ***

5 locks held by syz.1.232/5803:
 #0: ffff0000f63d2410 (sb_writers#14){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:493
 #1: ffff0000f4883d88 (&ovl_i_mutex_dir_key[depth]/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1074 [inline]
 #1: ffff0000f4883d88 (&ovl_i_mutex_dir_key[depth]/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3787 [inline]
 #1: ffff0000f4883d88 (&ovl_i_mutex_dir_key[depth]/1){+.+.}-{4:4}, at: __start_renaming+0x144/0x344 fs/namei.c:3880
 #2: ffff0000f2dd06d8 (&ovl_i_mutex_key[depth]#2){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1029 [inline]
 #2: ffff0000f2dd06d8 (&ovl_i_mutex_key[depth]#2){+.+.}-{4:4}, at: lock_two_nondirectories+0xc4/0x148 fs/inode.c:1254
 #3: ffff0000f4882d20 (&ovl_i_mutex_key[depth]/4){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1074 [inline]
 #3: ffff0000f4882d20 (&ovl_i_mutex_key[depth]/4){+.+.}-{4:4}, at: lock_two_nondirectories+0xe8/0x148 fs/inode.c:1256
 #4: ffff0000f2dd0a48 (&ovl_i_lock_key[depth]){+.+.}-{4:4}, at: ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:705 [inline]
 #4: ffff0000f2dd0a48 (&ovl_i_lock_key[depth]){+.+.}-{4:4}, at: ovl_copy_up_start+0x58/0x264 fs/overlayfs/util.c:735

stack backtrace:
CPU: 0 UID: 0 PID: 5803 Comm: syz.1.232 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 print_circular_bug+0x328/0x330 kernel/locking/lockdep.c:2043
 check_noncircular+0x158/0x174 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 kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x17c0/0x2ebc kernel/locking/lockdep.c:5237
 lock_acquire+0x140/0x364 kernel/locking/lockdep.c:5868
 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs/super.h:19 [inline]
 sb_start_write include/linux/fs/super.h:125 [inline]
 ovl_start_write+0xf0/0x324 fs/overlayfs/util.c:32
 ovl_copy_up_tmpfile fs/overlayfs/copy_up.c:864 [inline]
 ovl_do_copy_up fs/overlayfs/copy_up.c:986 [inline]
 ovl_copy_up_one fs/overlayfs/copy_up.c:1189 [inline]
 ovl_copy_up_flags+0xc58/0x28c0 fs/overlayfs/copy_up.c:1243
 ovl_copy_up+0x24/0x34 fs/overlayfs/copy_up.c:1282
 ovl_nlink_start+0x8c/0x350 fs/overlayfs/util.c:1168
 ovl_rename_start fs/overlayfs/dir.c:1189 [inline]
 ovl_rename+0x3b0/0xf80 fs/overlayfs/dir.c:1363
 vfs_rename+0xa78/0xd48 fs/namei.c:6064
 filename_renameat2+0x660/0x72c fs/namei.c:6182
 __do_sys_renameat2 fs/namei.c:6211 [inline]
 __se_sys_renameat2 fs/namei.c:6206 [inline]
 __arm64_sys_renameat2+0xec/0x11c fs/namei.c:6206
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
 el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/25 20:22 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 92e3f6ef4ffb 432fd51a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in ovl_copy_up_flags
2026/05/25 09:23 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 4b4362973b6f c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in ovl_copy_up_flags
* Struck through repros no longer work on HEAD.