From dfa7f709596be5ca46c070d4f8acbb344322056a Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Fri, 7 Feb 2020 19:29:28 +0200 Subject: [PATCH] drop_monitor: Do not cancel uninitialized work item Drop monitor uses a work item that takes care of constructing and sending netlink notifications to user space. In case drop monitor never started to monitor, then the work item is uninitialized and not associated with a function. Therefore, a stop command from user space results in canceling an uninitialized work item which leads to the following warning [1]. Fix this by not processing a stop command if drop monitor is not currently monitoring. [1] [ 31.735402] ------------[ cut here ]------------ [ 31.736470] WARNING: CPU: 0 PID: 143 at kernel/workqueue.c:3032 __flush_work+0x89f/0x9f0 ... [ 31.738120] CPU: 0 PID: 143 Comm: dwdump Not tainted 5.5.0-custom-09491-g16d4077796b8 #727 [ 31.741968] RIP: 0010:__flush_work+0x89f/0x9f0 ... [ 31.760526] Call Trace: [ 31.771689] __cancel_work_timer+0x2a6/0x3b0 [ 31.776809] net_dm_cmd_trace+0x300/0xef0 [ 31.777549] genl_rcv_msg+0x5c6/0xd50 [ 31.781005] netlink_rcv_skb+0x13b/0x3a0 [ 31.784114] genl_rcv+0x29/0x40 [ 31.784720] netlink_unicast+0x49f/0x6a0 [ 31.787148] netlink_sendmsg+0x7cf/0xc80 [ 31.790426] ____sys_sendmsg+0x620/0x770 [ 31.793458] ___sys_sendmsg+0xfd/0x170 [ 31.802216] __sys_sendmsg+0xdf/0x1a0 [ 31.806195] do_syscall_64+0xa0/0x540 [ 31.806885] entry_SYSCALL_64_after_hwframe+0x49/0xbe Fixes: 8e94c3bc922e ("drop_monitor: Allow user to start monitoring hardware drops") Signed-off-by: Ido Schimmel Reviewed-by: Jiri Pirko Signed-off-by: David S. Miller --- net/core/drop_monitor.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index ea46fc6aa883..31700e0c3928 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -1000,8 +1000,10 @@ static void net_dm_hw_monitor_stop(struct netlink_ext_ack *extack) { int cpu; - if (!monitor_hw) + if (!monitor_hw) { NL_SET_ERR_MSG_MOD(extack, "Hardware monitoring already disabled"); + return; + } monitor_hw = false; -- 2.39.2