From c74f2b2678f40b80265dd53556f1f778c8e1823f Mon Sep 17 00:00:00 2001 From: Stanislaw Gruszka Date: Fri, 26 Jul 2013 11:00:10 +0200 Subject: [PATCH] genetlink: release cb_lock before requesting additional module Requesting external module with cb_lock taken can result in the deadlock like showed below: [ 2458.111347] Showing all locks held in the system: [ 2458.111347] 1 lock held by NetworkManager/582: [ 2458.111347] #0: (cb_lock){++++++}, at: [] genl_rcv+0x19/0x40 [ 2458.111347] 1 lock held by modprobe/603: [ 2458.111347] #0: (cb_lock){++++++}, at: [] genl_lock_all+0x15/0x30 [ 2461.579457] SysRq : Show Blocked State [ 2461.580103] task PC stack pid father [ 2461.580103] NetworkManager D ffff880034b84500 4040 582 1 0x00000080 [ 2461.580103] ffff8800197ff720 0000000000000046 00000000001d5340 ffff8800197fffd8 [ 2461.580103] ffff8800197fffd8 00000000001d5340 ffff880019631700 7fffffffffffffff [ 2461.580103] ffff8800197ff880 ffff8800197ff878 ffff880019631700 ffff880019631700 [ 2461.580103] Call Trace: [ 2461.580103] [] schedule+0x29/0x70 [ 2461.580103] [] schedule_timeout+0x1c1/0x360 [ 2461.580103] [] ? mark_held_locks+0xbb/0x140 [ 2461.580103] [] ? _raw_spin_unlock_irq+0x2c/0x50 [ 2461.580103] [] ? trace_hardirqs_on_caller+0xfd/0x1c0 [ 2461.580103] [] wait_for_completion_killable+0xe8/0x170 [ 2461.580103] [] ? wake_up_state+0x20/0x20 [ 2461.580103] [] call_usermodehelper_exec+0x1a5/0x210 [ 2461.580103] [] ? wait_for_completion_killable+0x3d/0x170 [ 2461.580103] [] __request_module+0x1b3/0x370 [ 2461.580103] [] ? trace_hardirqs_on_caller+0xfd/0x1c0 [ 2461.580103] [] ctrl_getfamily+0x159/0x190 [ 2461.580103] [] genl_family_rcv_msg+0x1f4/0x2e0 [ 2461.580103] [] ? genl_family_rcv_msg+0x2e0/0x2e0 [ 2461.580103] [] genl_rcv_msg+0x8e/0xd0 [ 2461.580103] [] netlink_rcv_skb+0xa9/0xc0 [ 2461.580103] [] genl_rcv+0x28/0x40 [ 2461.580103] [] netlink_unicast+0xdd/0x190 [ 2461.580103] [] netlink_sendmsg+0x329/0x750 [ 2461.580103] [] sock_sendmsg+0x99/0xd0 [ 2461.580103] [] ? local_clock+0x5f/0x70 [ 2461.580103] [] ? lock_release_non_nested+0x308/0x350 [ 2461.580103] [] ___sys_sendmsg+0x39e/0x3b0 [ 2461.580103] [] ? kvm_clock_read+0x2f/0x50 [ 2461.580103] [] ? sched_clock+0x9/0x10 [ 2461.580103] [] ? sched_clock_local+0x1d/0x80 [ 2461.580103] [] ? sched_clock_cpu+0xa8/0x100 [ 2461.580103] [] ? trace_hardirqs_off+0xd/0x10 [ 2461.580103] [] ? local_clock+0x5f/0x70 [ 2461.580103] [] ? lock_release_holdtime.part.28+0xf/0x1a0 [ 2461.580103] [] ? fget_light+0xf9/0x510 [ 2461.580103] [] ? fget_light+0x3c/0x510 [ 2461.580103] [] __sys_sendmsg+0x42/0x80 [ 2461.580103] [] SyS_sendmsg+0x12/0x20 [ 2461.580103] [] system_call_fastpath+0x16/0x1b [ 2461.580103] modprobe D ffff88000f2c8000 4632 603 602 0x00000080 [ 2461.580103] ffff88000f04fba8 0000000000000046 00000000001d5340 ffff88000f04ffd8 [ 2461.580103] ffff88000f04ffd8 00000000001d5340 ffff8800377d4500 ffff8800377d4500 [ 2461.580103] ffffffff81d0b260 ffffffff81d0b268 ffffffff00000000 ffffffff81d0b2b0 [ 2461.580103] Call Trace: [ 2461.580103] [] schedule+0x29/0x70 [ 2461.580103] [] rwsem_down_write_failed+0xed/0x1a0 [ 2461.580103] [] ? update_cpu_load_active+0x10/0xb0 [ 2461.580103] [] call_rwsem_down_write_failed+0x13/0x20 [ 2461.580103] [] ? down_write+0x9d/0xb2 [ 2461.580103] [] ? genl_lock_all+0x15/0x30 [ 2461.580103] [] genl_lock_all+0x15/0x30 [ 2461.580103] [] genl_register_family+0x53/0x1f0 [ 2461.580103] [] ? 0xffffffffa01dbfff [ 2461.580103] [] genl_register_family_with_ops+0x20/0x80 [ 2461.580103] [] ? 0xffffffffa01dbfff [ 2461.580103] [] nl80211_init+0x24/0xf0 [cfg80211] [ 2461.580103] [] ? 0xffffffffa01dbfff [ 2461.580103] [] cfg80211_init+0x43/0xdb [cfg80211] [ 2461.580103] [] do_one_initcall+0xfa/0x1b0 [ 2461.580103] [] ? set_memory_nx+0x43/0x50 [ 2461.580103] [] load_module+0x1c6f/0x27f0 [ 2461.580103] [] ? store_uevent+0x40/0x40 [ 2461.580103] [] SyS_finit_module+0x86/0xb0 [ 2461.580103] [] system_call_fastpath+0x16/0x1b [ 2461.580103] Sched Debug Version: v0.10, 3.11.0-0.rc1.git4.1.fc20.x86_64 #1 Problem start to happen after adding net-pf-16-proto-16-family-nl80211 alias name to cfg80211 module by below commit (though that commit itself is perfectly fine): commit fb4e156886ce6e8309e912d8b370d192330d19d3 Author: Marcel Holtmann Date: Sun Apr 28 16:22:06 2013 -0700 nl80211: Add generic netlink module alias for cfg80211/nl80211 Reported-and-tested-by: Jeff Layton Reported-by: Richard W.M. Jones Signed-off-by: Stanislaw Gruszka Reviewed-by: Pravin B Shelar Signed-off-by: David S. Miller --- net/netlink/genetlink.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c index 2fd6dbea327a..1076fe16b122 100644 --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -877,8 +877,10 @@ static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info) #ifdef CONFIG_MODULES if (res == NULL) { genl_unlock(); + up_read(&cb_lock); request_module("net-pf-%d-proto-%d-family-%s", PF_NETLINK, NETLINK_GENERIC, name); + down_read(&cb_lock); genl_lock(); res = genl_family_find_byname(name); } -- 2.20.1