[syzbot] possible deadlock in sctp_addr_wq_timeout_handler

syzbot
2021-04-30T19:18:32Z

Hello,

syzbot found the following issue on:

HEAD commit: 2a1d7946 Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159af1c1d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9404cfa686df2c05
dashboard link: https://syzkaller.appspot.com/bug?extid=959223586843e69a2674
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11613d71d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12be674dd00000

The issue was bisected to:

commit 997acaf6b4b59c6a9c259740312a69ea549cc684
Author: Mark Rutland <mark.rutland@arm.com>
Date: Mon Jan 11 15:37:07 2021 +0000

lockdep: report broken irq restoration

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17c36a5dd00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=14236a5dd00000
console output: https://syzkaller.appspot.com/x/log.txt?x=10236a5dd00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+959223586843e69a2674@syzkaller.appspotmail.com
Fixes: 997acaf6b4b5 ("lockdep: report broken irq restoration")

======================================================
WARNING: possible circular locking dependency detected
5.12.0-rc8-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor044/8536 is trying to acquire lock:
ffff8880183933a0 (slock-AF_INET6){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
ffff8880183933a0 (slock-AF_INET6){+.-.}-{2:2}, at: sctp_addr_wq_timeout_handler+0x1a1/0x550 net/sctp/protocol.c:666

but task is already holding lock:
ffffffff8d659620 (&net->sctp.addr_wq_lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:359 [inline]
ffffffff8d659620 (&net->sctp.addr_wq_lock){+.-.}-{2:2}, at: sctp_addr_wq_timeout_handler+0x38/0x550 net/sctp/protocol.c:626

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&net->sctp.addr_wq_lock){+.-.}-{2:2}:
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:175
spin_lock_bh include/linux/spinlock.h:359 [inline]
sctp_destroy_sock+0x204/0x440 net/sctp/socket.c:5028
sctp_v6_destroy_sock+0x11/0x20 net/sctp/socket.c:9528
sk_common_release+0x64/0x390 net/core/sock.c:3264
sctp_close+0x4da/0x940 net/sctp/socket.c:1531
inet_release+0x12e/0x280 net/ipv4/af_inet.c:431
inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:478
__sock_release+0xcd/0x280 net/socket.c:599
sock_close+0x18/0x20 net/socket.c:1258
__fput+0x288/0x920 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:140
exit_task_work include/linux/task_work.h:30 [inline]
do_exit+0xbfc/0x2a60 kernel/exit.c:825
do_group_exit+0x125/0x310 kernel/exit.c:922
__do_sys_exit_group kernel/exit.c:933 [inline]
__se_sys_exit_group kernel/exit.c:931 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (slock-AF_INET6){+.-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:2937 [inline]
check_prevs_add kernel/locking/lockdep.c:3060 [inline]
validate_chain kernel/locking/lockdep.c:3675 [inline]
__lock_acquire+0x2b14/0x54c0 kernel/locking/lockdep.c:4901
lock_acquire kernel/locking/lockdep.c:5511 [inline]
lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5476
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
sctp_addr_wq_timeout_handler+0x1a1/0x550 net/sctp/protocol.c:666
call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1431
expire_timers kernel/time/timer.c:1476 [inline]
__run_timers.part.0+0x67c/0xa50 kernel/time/timer.c:1745
__run_timers kernel/time/timer.c:1726 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1758
__do_softirq+0x29b/0x9f6 kernel/softirq.c:345
invoke_softirq kernel/softirq.c:221 [inline]
__irq_exit_rcu kernel/softirq.c:422 [inline]
irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:191
__debug_check_no_obj_freed lib/debugobjects.c:997 [inline]
debug_check_no_obj_freed+0x20c/0x420 lib/debugobjects.c:1018
slab_free_hook mm/slub.c:1554 [inline]
slab_free_freelist_hook+0x147/0x210 mm/slub.c:1600
slab_free mm/slub.c:3161 [inline]
kmem_cache_free+0x8a/0x740 mm/slub.c:3177
free_fs_struct fs/fs_struct.c:92 [inline]
exit_fs+0x123/0x170 fs/fs_struct.c:108
do_exit+0xbca/0x2a60 kernel/exit.c:821
do_group_exit+0x125/0x310 kernel/exit.c:922
__do_sys_exit_group kernel/exit.c:933 [inline]
__se_sys_exit_group kernel/exit.c:931 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&net->sctp.addr_wq_lock);
lock(slock-AF_INET6);
lock(&net->sctp.addr_wq_lock);
lock(slock-AF_INET6);

*** DEADLOCK ***

2 locks held by syz-executor044/8536:
#0: ffffc90000007d78 ((&net->sctp.addr_wq_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:35 [inline]
#0: ffffc90000007d78 ((&net->sctp.addr_wq_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x6b0 kernel/time/timer.c:1421
#1: ffffffff8d659620 (&net->sctp.addr_wq_lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:359 [inline]
#1: ffffffff8d659620 (&net->sctp.addr_wq_lock){+.-.}-{2:2}, at: sctp_addr_wq_timeout_handler+0x38/0x550 net/sctp/protocol.c:626

stack backtrace:
CPU: 0 PID: 8536 Comm: syz-executor044 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2128
check_prev_add kernel/locking/lockdep.c:2937 [inline]
check_prevs_add kernel/locking/lockdep.c:3060 [inline]
validate_chain kernel/locking/lockdep.c:3675 [inline]
__lock_acquire+0x2b14/0x54c0 kernel/locking/lockdep.c:4901
lock_acquire kernel/locking/lockdep.c:5511 [inline]
lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5476
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
sctp_addr_wq_timeout_handler+0x1a1/0x550 net/sctp/protocol.c:666
call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1431
expire_timers kernel/time/timer.c:1476 [inline]
__run_timers.part.0+0x67c/0xa50 kernel/time/timer.c:1745
__run_timers kernel/time/timer.c:1726 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1758
__do_softirq+0x29b/0x9f6 kernel/softirq.c:345
invoke_softirq kernel/softirq.c:221 [inline]
__irq_exit_rcu kernel/softirq.c:422 [inline]
irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
</IRQ>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:191
Code: 74 24 10 e8 4a f9 53 f8 48 89 ef e8 82 af 54 f8 81 e3 00 02 00 00 75 25 9c 58 f6 c4 02 75 2d 48 85 db 74 01 fb bf 01 00 00 00 <e8> 63 7d 48 f8 65 8b 05 0c 48 fc 76 85 c0 74 0a 5b 5d c3 e8 d0 3c
RSP: 0018:ffffc9000173fc50 EFLAGS: 00000206
RAX: 0000000000000002 RBX: 0000000000000200 RCX: 1ffffffff1b89e11
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffffff9006cf00 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff8179e4c8 R11: 000000000000003f R12: 1ffffffff200d9df
R13: 0000000000000000 R14: dead000000000100 R15: dffffc0000000000
__debug_check_no_obj_freed lib/debugobjects.c:997 [inline]
debug_check_no_obj_freed+0x20c/0x420 lib/debugobjects.c:1018
slab_free_hook mm/slub.c:1554 [inline]
slab_free_freelist_hook+0x147/0x210 mm/slub.c:1600
slab_free mm/slub.c:3161 [inline]
kmem_cache_free+0x8a/0x740 mm/slub.c:3177
free_fs_struct fs/fs_struct.c:92 [inline]
exit_fs+0x123/0x170 fs/fs_struct.c:108
do_exit+0xbca/0x2a60 kernel/exit.c:821
do_group_exit+0x125/0x310 kernel/exit.c:922
__do_sys_exit_group kernel/exit.c:933 [inline]
__se_sys_exit_group kernel/exit.c:931 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43ea79
Code: Unable to access opcode bytes at RIP 0x43ea4f.
RSP: 002b:00007ffdbc348058 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000004b0330 RCX: 000000000043ea79
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000246 R12: 00000000004b0330
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001

---
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