From: Ido Schimmel idosch@mellanox.com
[ Upstream commit dfa7f709596be5ca46c070d4f8acbb344322056a ]
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 idosch@mellanox.com Reviewed-by: Jiri Pirko jiri@mellanox.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/drop_monitor.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -1004,8 +1004,10 @@ static void net_dm_hw_monitor_stop(struc { int cpu;
- if (!monitor_hw) + if (!monitor_hw) { NL_SET_ERR_MSG_MOD(extack, "Hardware monitoring already disabled"); + return; + }
monitor_hw = false;