Hello,
While running syzkaller fuzzer I have got the following deadlock
report. The kernel version is 4.8.0+ (on Oct 7 commit
d1f5323370fceaed43a7ee38f4c7bfc7e70f28d0). Unfortunately I failed to find a
reproducer for it.
===============================================================================
[ INFO: possible circular locking dependency detected ]
4.8.0+ #39 Not tainted
-------------------------------------------------------
syz-executor/21301 is trying to acquire lock:
([ 165.136033] rtnl_mutex
[<ffffffff84ce81d7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
but task is already holding lock:
([ 165.136033] sk_lock-AF_INET6
[<ffffffff85245db1>] do_ipv6_setsockopt.isra.7+0x1f1/0x2960
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
:
[ 165.136033] [<ffffffff81427398>] lock_acquire+0x1a8/0x380
kernel/locking/lockdep.c:3746
[ 165.136033] [<ffffffff84c54c0b>] lock_sock_nested+0xcb/0x120
net/core/sock.c:2493
[ 165.136033] [<ffffffff85245e28>]
do_ipv6_setsockopt.isra.7+0x268/0x2960
[ 165.136033] [<ffffffff852485bb>] ipv6_setsockopt+0x9b/0x140
[ 165.136033] [<ffffffff8525a6c5>] udpv6_setsockopt+0x45/0x80
net/ipv6/udp.c:1344
[ 165.136033] [<ffffffff84c4ed85>] sock_common_setsockopt+0x95/0xd0
net/core/sock.c:2688
[ 165.136033] [< inline >] SYSC_setsockopt net/socket.c:1742
[ 165.136033] [<ffffffff84c4bff8>] SyS_setsockopt+0x158/0x240
net/socket.c:1721
[ 165.136033] [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
:
[ 165.136033] [< inline >] check_prev_add
kernel/locking/lockdep.c:1829
[ 165.136033] [< inline >] check_prevs_add
kernel/locking/lockdep.c:1939
[ 165.136033] [< inline >] validate_chain
kernel/locking/lockdep.c:2266
[ 165.136033] [<ffffffff81424d19>] __lock_acquire+0x35a9/0x4bc0
kernel/locking/lockdep.c:3335
[ 165.136033] [<ffffffff81427398>] lock_acquire+0x1a8/0x380
kernel/locking/lockdep.c:3746
[ 165.136033] [< inline >] __mutex_lock_common
kernel/locking/mutex.c:521
[ 165.136033] [<ffffffff85e44721>] mutex_lock_nested+0xb1/0x860
kernel/locking/mutex.c:621
[ 165.136033] [<ffffffff84ce81d7>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:70
[ 165.136033] [<ffffffff8528116e>] ipv6_sock_mc_close+0xfe/0x350
net/ipv6/mcast.c:288
[ 165.136033] [<ffffffff85247ebc>]
do_ipv6_setsockopt.isra.7+0x22fc/0x2960
[ 165.136033] [<ffffffff852485bb>] ipv6_setsockopt+0x9b/0x140
[ 165.136033] [<ffffffff8525a6c5>] udpv6_setsockopt+0x45/0x80
net/ipv6/udp.c:1344
[ 165.136033] [<ffffffff84c4ed85>] sock_common_setsockopt+0x95/0xd0
net/core/sock.c:2688
[ 165.136033] [< inline >] SYSC_setsockopt net/socket.c:1742
[ 165.136033] [<ffffffff84c4bff8>] SyS_setsockopt+0x158/0x240
net/socket.c:1721
[ 165.136033] [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock([ 165.136033] sk_lock-AF_INET6
);
lock([ 165.136033] rtnl_mutex
);
lock([ 165.136033] sk_lock-AF_INET6
);
lock([ 165.136033] rtnl_mutex
);
*** DEADLOCK ***
1 lock held by syz-executor/21301:
#0: [ 165.136033] (
stack backtrace:
CPU: 1 PID: 21301 Comm: syz-executor Not tainted 4.8.0+ #39
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
ffff880017217580 ffffffff829f835b ffffffff88d65790 ffffffff88d65790
ffffffff88dc6b70 ffff880016f41fd8 ffff8800172175d0 ffffffff8141df18
ffff880016f41ffa dffffc0000000000 000000008764c180 ffff880016f41fd8
Call Trace:
[<ffffffff829f835b>] dump_stack+0xb3/0x118 lib/dump_stack.c:15
[<ffffffff8141df18>] print_circular_bug+0x288/0x340
kernel/locking/lockdep.c:1202
[< inline >] check_prev_add kernel/locking/lockdep.c:1829
[< inline >] check_prevs_add kernel/locking/lockdep.c:1939
[< inline >] validate_chain kernel/locking/lockdep.c:2266
[<ffffffff81424d19>] __lock_acquire+0x35a9/0x4bc0 kernel/locking/lockdep.c:3335
[<ffffffff81427398>] lock_acquire+0x1a8/0x380 kernel/locking/lockdep.c:3746
[< inline >] __mutex_lock_common kernel/locking/mutex.c:521
[<ffffffff85e44721>] mutex_lock_nested+0xb1/0x860 kernel/locking/mutex.c:621
[<ffffffff84ce81d7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
[<ffffffff8528116e>] ipv6_sock_mc_close+0xfe/0x350 net/ipv6/mcast.c:288
[<ffffffff85247ebc>] do_ipv6_setsockopt.isra.7+0x22fc/0x2960
[<ffffffff852485bb>] ipv6_setsockopt+0x9b/0x140
[<ffffffff8525a6c5>] udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1344
[<ffffffff84c4ed85>] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2688
[< inline >] SYSC_setsockopt net/socket.c:1742
[<ffffffff84c4bff8>] SyS_setsockopt+0x158/0x240 net/socket.c:1721
[<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
Thanks && Best Regards,
Baozeng Ding
