syzbot


possible deadlock in efivarfs_actor

Status: upstream: reported C repro on 2025/03/09 02:52
Subsystems: fs efi
[Documentation on labels]
Reported-by: syzbot+019072ad24ab1d948228@syzkaller.appspotmail.com
Fix commit: dec1277875a5 efivarfs: use I_MUTEX_CHILD nested lock to traverse variables on resume
Patched on: [ci-qemu-gce-upstream-auto ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb], missing on: [ci-qemu-native-arm64-kvm ci-qemu2-arm32 ci-qemu2-riscv64]
First crash: 53d, last: 33d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [efi?] [fs?] possible deadlock in efivarfs_actor 7 (9) 2025/03/10 23:58
Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/03/09 09:21 28m hdanton@sina.com patch upstream OK log

Sample crash report:
efivarfs: resyncing variable state
============================================
WARNING: possible recursive locking detected
6.14.0-rc7-syzkaller-ga2392f333575 #0 Not tainted
--------------------------------------------
syz-executor372/6438 is trying to acquire lock:
ffff0000c6c8e558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline]
ffff0000c6c8e558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: efivarfs_actor+0x1b8/0x2b8 fs/efivarfs/super.c:424

but task is already holding lock:
ffff0000c70c6558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: iterate_dir+0x3b4/0x5f4 fs/readdir.c:101

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&sb->s_type->i_mutex_key#16);
  lock(&sb->s_type->i_mutex_key#16);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by syz-executor372/6438:
 #0: ffff80008fc57588 (system_transition_mutex){+.+.}-{4:4}, at: lock_system_sleep+0x68/0xc0 kernel/power/main.c:56
 #1: ffff80008fc760f0 ((pm_chain_head).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x58/0xa0 kernel/notifier.c:379
 #2: ffff0000c70c6558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: iterate_dir+0x3b4/0x5f4 fs/readdir.c:101

stack backtrace:
CPU: 0 UID: 0 PID: 6438 Comm: syz-executor372 Not tainted 6.14.0-rc7-syzkaller-ga2392f333575 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 print_deadlock_bug+0x4e8/0x668 kernel/locking/lockdep.c:3039
 check_deadlock kernel/locking/lockdep.c:3091 [inline]
 validate_chain kernel/locking/lockdep.c:3893 [inline]
 __lock_acquire+0x6240/0x7904 kernel/locking/lockdep.c:5228
 lock_acquire+0x23c/0x724 kernel/locking/lockdep.c:5851
 down_write+0x50/0xc0 kernel/locking/rwsem.c:1577
 inode_lock include/linux/fs.h:877 [inline]
 efivarfs_actor+0x1b8/0x2b8 fs/efivarfs/super.c:424
 dir_emit include/linux/fs.h:3851 [inline]
 dcache_readdir+0x2dc/0x4e8 fs/libfs.c:209
 iterate_dir+0x46c/0x5f4 fs/readdir.c:108
 efivarfs_pm_notify+0x2f4/0x350 fs/efivarfs/super.c:519
 notifier_call_chain+0x1c4/0x550 kernel/notifier.c:85
 blocking_notifier_call_chain+0x70/0xa0 kernel/notifier.c:380
 pm_notifier_call_chain+0x2c/0x3c kernel/power/main.c:109
 snapshot_release+0x128/0x1b8 kernel/power/user.c:125
 __fput+0x340/0x760 fs/file_table.c:464
 ____fput+0x20/0x30 fs/file_table.c:492
 task_work_run+0x230/0x2e0 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 do_notify_resume+0x178/0x1f4 arch/arm64/kernel/entry-common.c:151
 exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]
 el0_svc+0xac/0x168 arch/arm64/kernel/entry-common.c:745
 el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/03/25 20:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci a2392f333575 875573af .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/25 17:30 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci a2392f333575 875573af .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/25 15:04 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci a2392f333575 875573af .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/25 12:39 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci a2392f333575 875573af .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/05 06:23 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci e056da87c780 c3901742 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/13 05:47 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 78e3fd2b7e4b 1a5d9317 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/05 02:43 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci e056da87c780 c3901742 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
2025/03/05 02:41 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci e056da87c780 c3901742 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in efivarfs_actor
* Struck through repros no longer work on HEAD.