Hi all, While fuzzing with syzkaller inside a KVM tools guest running the latest -next, I saw the following warning:
[ 2391.993558] ====================================================== [ 2391.995441] [ INFO: possible circular locking dependency detected ] [ 2391.995771] 4.3.0-rc6-next-20151022-sasha-00042-g2b253a1-dirty #2618 Not tainted [ 2391.995771] ------------------------------------------------------- [ 2391.995771] syzkaller_execu/14105 is trying to acquire lock: [ 2391.995771] (rtnl_mutex){+.+.+.}, at: rtnl_lock (net/core/rtnetlink.c:71) [ 2391.995771] Mutex: counter: 1 owner: None [ 2391.995771] [ 2391.995771] but task is already holding lock: [ 2391.995771] (sk_lock-AF_INET){+.+.+.}, at: do_ip_getsockopt (net/ipv4/ip_sockglue.c:1274) [ 2391.995771] [ 2391.995771] which lock already depends on the new lock. [ 2391.995771] [ 2391.995771] [ 2391.995771] the existing dependency chain (in reverse order) is: [ 2391.995771] -> #1 (sk_lock-AF_INET){+.+.+.}: [ 2391.995771] lock_acquire (kernel/locking/lockdep.c:3620) [ 2391.995771] lock_sock_nested (include/linux/bottom_half.h:31 net/core/sock.c:2411) [ 2391.995771] do_ip_setsockopt.isra.9 (net/ipv4/ip_sockglue.c:623) [ 2391.995771] ip_setsockopt (net/ipv4/ip_sockglue.c:1202) [ 2391.995771] ffffffffffffff, 0x0) [ 2391.995771] sock_common_setsockopt (net/core/sock.c:2610) [ 2391.995771] SyS_setsockopt (net/socket.c:1756 net/socket.c:1736) [ 2391.995771] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188) [ 2391.995771] -> #0 (rtnl_mutex){+.+.+.}: [ 2391.995771] __lock_acquire (kernel/locking/lockdep.c:1877 kernel/locking/lockdep.c:1982 kernel/locking/lockdep.c:2168 kernel/locking/lockdep.c:3239) [ 2391.995771] lock_acquire (kernel/locking/lockdep.c:3620) [ 2391.995771] mutex_lock_nested (kernel/locking/mutex.c:526 kernel/locking/mutex.c:618) [ 2391.995771] rtnl_lock (net/core/rtnetlink.c:71) [ 2391.995771] ip_mc_msfget (net/ipv4/igmp.c:2400) [ 2391.995771] do_ip_getsockopt (net/ipv4/ip_sockglue.c:1401) [ 2391.995771] ip_getsockopt (net/ipv4/ip_sockglue.c:1498) [ 2391.995771] raw_getsockopt (net/ipv4/raw.c:851) [ 2391.995771] sock_common_getsockopt (net/core/sock.c:2569) [ 2391.995771] SyS_getsockopt (net/socket.c:1787 net/socket.c:1770) [ 2391.995771] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188) [ 2391.995771] [ 2391.995771] other info that might help us debug this: [ 2391.995771] [ 2391.995771] Possible unsafe locking scenario: [ 2391.995771] [ 2391.995771] CPU0 CPU1 [ 2391.995771] ---- ---- [ 2391.995771] lock(sk_lock-AF_INET); [ 2391.995771] lock(rtnl_mutex); [ 2391.995771] lock(sk_lock-AF_INET); [ 2391.995771] lock(rtnl_mutex); [ 2391.995771] [ 2391.995771] *** DEADLOCK *** [ 2391.995771] [ 2391.995771] 1 lock held by syzkaller_execu/14105: [ 2391.995771] #0: (sk_lock-AF_INET){+.+.+.}, at: do_ip_getsockopt (net/ipv4/ip_sockglue.c:1274) [ 2391.995771] [ 2391.995771] stack backtrace: [ 2391.995771] CPU: 1 PID: 14105 Comm: syzkaller_execu Not tainted 4.3.0-rc6-next-20151022-sasha-00042-g2b253a1-dirty #2618 [ 2391.995771] 0000000000000001 00000000c179c8c9 ffff8800a403f550 ffffffffade32a2b [ 2391.995771] ffffffffbb7f5a50 ffffffffbb84a4a0 ffffffffbb7f5a50 ffff8800a403f5a0 [ 2391.995771] ffffffffac43fca8 ffff8800a403f690 00000000a3e18000 ffff8800a3e18000 [ 2391.995771] Call Trace: [ 2391.995771] dump_stack (lib/dump_stack.c:52) [ 2391.995771] print_circular_bug (kernel/locking/lockdep.c:1250) [ 2391.995771] __lock_acquire (kernel/locking/lockdep.c:1877 kernel/locking/lockdep.c:1982 kernel/locking/lockdep.c:2168 kernel/locking/lockdep.c:3239) [ 2391.995771] lock_acquire (kernel/locking/lockdep.c:3620) [ 2391.995771] mutex_lock_nested (kernel/locking/mutex.c:526 kernel/locking/mutex.c:618) [ 2391.995771] rtnl_lock (net/core/rtnetlink.c:71) [ 2391.995771] ip_mc_msfget (net/ipv4/igmp.c:2400) [ 2391.995771] do_ip_getsockopt (net/ipv4/ip_sockglue.c:1401) [ 2391.995771] ip_getsockopt (net/ipv4/ip_sockglue.c:1498) [ 2391.995771] raw_getsockopt (net/ipv4/raw.c:851) [ 2391.995771] sock_common_getsockopt (net/core/sock.c:2569) [ 2391.995771] SyS_getsockopt (net/socket.c:1787 net/socket.c:1770) [ 2391.995771] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188) Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html