syzbot


possible deadlock in sys_mbind (2)

Status: upstream: reported on 2025/03/04 10:10
Reported-by: syzbot+9c41b8900a32c1dcc9d8@syzkaller.appspotmail.com
First crash: 136d, last: 61d
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in sys_mbind (2) 4 1 108d 108d 0/3 auto-obsoleted due to no activity on 2025/07/09 17:25
linux-5.15 possible deadlock in sys_mbind 4 7 343d 359d 0/3 auto-obsoleted due to no activity on 2024/11/16 19:34
linux-6.1 possible deadlock in sys_mbind 4 1 346d 346d 0/3 auto-obsoleted due to no activity on 2024/11/13 14:21

Sample crash report:
REISERFS (device loop1): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
5.15.182-syzkaller #0 Not tainted
------------------------------------------------------
syz.1.140/4604 is trying to acquire lock:
ffff0000d9396090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27

but task is already holding lock:
ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: do_mbind mm/mempolicy.c:1299 [inline]
ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: kernel_mbind mm/mempolicy.c:1472 [inline]
ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: __do_sys_mbind mm/mempolicy.c:1479 [inline]
ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: __se_sys_mbind mm/mempolicy.c:1475 [inline]
ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: __arm64_sys_mbind+0x524/0x7b8 mm/mempolicy.c:1475

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&mm->mmap_lock){++++}-{3:3}:
       __might_fault+0xc8/0x128 mm/memory.c:5357
       reiserfs_ioctl+0x144/0x4b4 fs/reiserfs/ioctl.c:96
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl fs/ioctl.c:860 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (&sbi->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
       lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27
       map_block_for_writepage fs/reiserfs/inode.c:2396 [inline]
       reiserfs_write_full_page fs/reiserfs/inode.c:2593 [inline]
       reiserfs_writepage+0x708/0x2c18 fs/reiserfs/inode.c:2745
       writeout mm/migrate.c:837 [inline]
       fallback_migrate_page mm/migrate.c:861 [inline]
       move_to_new_page+0x5e0/0xc28 mm/migrate.c:912
       __unmap_and_move mm/migrate.c:1077 [inline]
       unmap_and_move mm/migrate.c:1218 [inline]
       migrate_pages+0x197c/0x3020 mm/migrate.c:1495
       do_mbind mm/mempolicy.c:1325 [inline]
       kernel_mbind mm/mempolicy.c:1472 [inline]
       __do_sys_mbind mm/mempolicy.c:1479 [inline]
       __se_sys_mbind mm/mempolicy.c:1475 [inline]
       __arm64_sys_mbind+0x618/0x7b8 mm/mempolicy.c:1475
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz.1.140/4604:
 #0: ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 #0: ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: do_mbind mm/mempolicy.c:1299 [inline]
 #0: ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: kernel_mbind mm/mempolicy.c:1472 [inline]
 #0: ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: __do_sys_mbind mm/mempolicy.c:1479 [inline]
 #0: ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: __se_sys_mbind mm/mempolicy.c:1475 [inline]
 #0: ffff0000d2970118 (&mm->mmap_lock){++++}-{3:3}, at: __arm64_sys_mbind+0x524/0x7b8 mm/mempolicy.c:1475

stack backtrace:
CPU: 1 PID: 4604 Comm: syz.1.140 Not tainted 5.15.182-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2011
 check_noncircular+0x240/0x2d4 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
 __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
 reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27
 map_block_for_writepage fs/reiserfs/inode.c:2396 [inline]
 reiserfs_write_full_page fs/reiserfs/inode.c:2593 [inline]
 reiserfs_writepage+0x708/0x2c18 fs/reiserfs/inode.c:2745
 writeout mm/migrate.c:837 [inline]
 fallback_migrate_page mm/migrate.c:861 [inline]
 move_to_new_page+0x5e0/0xc28 mm/migrate.c:912
 __unmap_and_move mm/migrate.c:1077 [inline]
 unmap_and_move mm/migrate.c:1218 [inline]
 migrate_pages+0x197c/0x3020 mm/migrate.c:1495
 do_mbind mm/mempolicy.c:1325 [inline]
 kernel_mbind mm/mempolicy.c:1472 [inline]
 __do_sys_mbind mm/mempolicy.c:1479 [inline]
 __se_sys_mbind mm/mempolicy.c:1475 [inline]
 __arm64_sys_mbind+0x618/0x7b8 mm/mempolicy.c:1475
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/18 06:27 linux-5.15.y 3b8db0e4f263 f41472b0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in sys_mbind
2025/03/04 10:10 linux-5.15.y c16c81c81336 c3901742 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 possible deadlock in sys_mbind
* Struck through repros no longer work on HEAD.