======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.4.4016/18351 is trying to acquire lock:
ffff888032c36738 (&mm->mmap_lock){++++}-{4:4}, at: __might_fault+0xaf/0x130 mm/memory.c:7249
but task is already holding lock:
ffff88804be941f0 (&ctx->map_changing_lock){++++}-{4:4}, at: mfill_get_vma+0x162/0x660 mm/userfaultfd.c:226
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&ctx->map_changing_lock){++++}-{4:4}:
down_write+0x96/0x200 kernel/locking/rwsem.c:1625
mremap_userfaultfd_prep+0x117/0x190 fs/userfaultfd.c:753
copy_vma_and_data mm/mremap.c:1234 [inline]
move_vma+0xc31/0x1800 mm/mremap.c:1292
mremap_to+0x788/0x850 mm/mremap.c:1416
remap_move mm/mremap.c:1890 [inline]
do_mremap mm/mremap.c:1933 [inline]
__do_sys_mremap mm/mremap.c:1997 [inline]
__se_sys_mremap+0xb7d/0xfc0 mm/mremap.c:1965
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&mm->mmap_lock){++++}-{4:4}:
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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
__might_fault+0xcb/0x130 mm/memory.c:7249
userfaultfd_continue fs/userfaultfd.c:1813 [inline]
userfaultfd_ioctl+0x2372/0x4c70 fs/userfaultfd.c:2071
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(&ctx->map_changing_lock);
lock(&mm->mmap_lock);
lock(&ctx->map_changing_lock);
rlock(&mm->mmap_lock);
*** DEADLOCK ***
2 locks held by syz.4.4016/18351:
#0: ffff888033b97448 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500 mm/mmap_lock.c:310
#1: ffff88804be941f0 (&ctx->map_changing_lock){++++}-{4:4}, at: mfill_get_vma+0x162/0x660 mm/userfaultfd.c:226
stack backtrace:
CPU: 0 UID: 0 PID: 18351 Comm: syz.4.4016 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
__might_fault+0xcb/0x130 mm/memory.c:7249
userfaultfd_continue fs/userfaultfd.c:1813 [inline]
userfaultfd_ioctl+0x2372/0x4c70 fs/userfaultfd.c:2071
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f105f99c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f10608f3028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f105fc16090 RCX: 00007f105f99c799
RDX: 0000200000000280 RSI: 00000000c020aa07 RDI: 0000000000000009
RBP: 00007f105fa32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f105fc16128 R14: 00007f105fc16090 R15: 00007fff173dac88
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 1 UID: 0 PID: 18351 Comm: syz.4.4016 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:rwsem_mark_wake+0xfa/0x7c0 kernel/locking/rwsem.c:445
Code: 01 00 74 08 4c 89 f7 e8 e4 c2 8d 00 4c 89 74 24 10 4d 8b 26 4d 8d 74 24 18 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 75 06 00 00 41 83 3e 00 74 64 4c 89 ef be
RSP: 0018:ffffc900059cf320 EFLAGS: 00010006
RAX: 0000000000000003 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: 1ffff92000b39e70 RSI: 0000000000000000 RDI: ffff888032c366d0
RBP: ffffc900059cf420 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000b39e80 R12: 0000000000000000
R13: ffff888032c366d0 R14: 0000000000000018 R15: ffffc900059cf5a0
FS: 00007f10608f36c0(0000) GS:ffff888124ee0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000480 CR3: 0000000057ad4000 CR4: 00000000003526f0
Call Trace:
rwsem_del_wake_waiter+0x25d/0x2e0 kernel/locking/rwsem.c:612
rwsem_down_write_slowpath+0xa6f/0x1080 kernel/locking/rwsem.c:1234
__down_write_common kernel/locking/rwsem.c:1347 [inline]
__down_write_killable kernel/locking/rwsem.c:1361 [inline]
down_write_killable+0x1eb/0x240 kernel/locking/rwsem.c:1639
mmap_write_lock_killable include/linux/mmap_lock.h:554 [inline]
dup_mmap+0x181/0x1d90 mm/mmap.c:1740
dup_mm kernel/fork.c:1536 [inline]
copy_mm+0x14d/0x690 kernel/fork.c:1588
copy_process+0x1efd/0x4430 kernel/fork.c:2263
kernel_clone+0x248/0x8e0 kernel/fork.c:2711
__do_sys_clone kernel/fork.c:2853 [inline]
__se_sys_clone kernel/fork.c:2836 [inline]
__x64_sys_clone+0x1e4/0x260 kernel/fork.c:2836
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f105f99c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f10608f2fd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f105fc16090 RCX: 00007f105f99c799
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000001000
RBP: 00007f105fa32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f105fc16128 R14: 00007f105fc16090 R15: 00007fff173dac88
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:rwsem_mark_wake+0xfa/0x7c0 kernel/locking/rwsem.c:445
Code: 01 00 74 08 4c 89 f7 e8 e4 c2 8d 00 4c 89 74 24 10 4d 8b 26 4d 8d 74 24 18 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 75 06 00 00 41 83 3e 00 74 64 4c 89 ef be
RSP: 0018:ffffc900059cf320 EFLAGS: 00010006
RAX: 0000000000000003 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: 1ffff92000b39e70 RSI: 0000000000000000 RDI: ffff888032c366d0
RBP: ffffc900059cf420 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000b39e80 R12: 0000000000000000
R13: ffff888032c366d0 R14: 0000000000000018 R15: ffffc900059cf5a0
FS: 00007f10608f36c0(0000) GS:ffff888124ee0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000480 CR3: 0000000057ad4000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 01 00 add %eax,(%rax)
2: 74 08 je 0xc
4: 4c 89 f7 mov %r14,%rdi
7: e8 e4 c2 8d 00 call 0x8dc2f0
c: 4c 89 74 24 10 mov %r14,0x10(%rsp)
11: 4d 8b 26 mov (%r14),%r12
14: 4d 8d 74 24 18 lea 0x18(%r12),%r14
19: 4c 89 f0 mov %r14,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
27: fc ff df
* 2a: 0f b6 04 08 movzbl (%rax,%rcx,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 0f 85 75 06 00 00 jne 0x6ab
36: 41 83 3e 00 cmpl $0x0,(%r14)
3a: 74 64 je 0xa0
3c: 4c 89 ef mov %r13,%rdi
3f: be .byte 0xbe