The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Thanks, Sasha
------------------ original commit in Linus's tree ------------------
From 9398e9c0b1d44eeb700e9e766c02bcc765c82570 Mon Sep 17 00:00:00 2001
From: Ido Schimmel idosch@nvidia.com Date: Wed, 10 Mar 2021 12:28:01 +0200 Subject: [PATCH] drop_monitor: Perform cleanup upon probe registration failure
In the rare case that drop_monitor fails to register its probe on the 'napi_poll' tracepoint, it will not deactivate its hysteresis timer as part of the error path. If the hysteresis timer was armed by the shortly lived 'kfree_skb' probe and user space retries to initiate tracing, a warning will be emitted for trying to initialize an active object [1].
Fix this by properly undoing all the operations that were done prior to probe registration, in both software and hardware code paths.
Note that syzkaller managed to fail probe registration by injecting a slab allocation failure [2].
[1] ODEBUG: init active (active state 0) object type: timer_list hint: sched_send_work+0x0/0x60 include/linux/list.h:135 WARNING: CPU: 1 PID: 8649 at lib/debugobjects.c:505 debug_print_object+0x16e/0x250 lib/debugobjects.c:505 Modules linked in: CPU: 1 PID: 8649 Comm: syz-executor.0 Not tainted 5.11.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:505 [...] Call Trace: __debug_object_init+0x524/0xd10 lib/debugobjects.c:588 debug_timer_init kernel/time/timer.c:722 [inline] debug_init kernel/time/timer.c:770 [inline] init_timer_key+0x2d/0x340 kernel/time/timer.c:814 net_dm_trace_on_set net/core/drop_monitor.c:1111 [inline] set_all_monitor_traces net/core/drop_monitor.c:1188 [inline] net_dm_monitor_start net/core/drop_monitor.c:1295 [inline] net_dm_cmd_trace+0x720/0x1220 net/core/drop_monitor.c:1339 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:739 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:800 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502 genl_rcv+0x24/0x40 net/netlink/genetlink.c:811 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:672 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2348 ___sys_sendmsg+0xf3/0x170 net/socket.c:2402 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2435 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae
[2] FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 1 CPU: 1 PID: 8645 Comm: syz-executor.0 Not tainted 5.11.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: dump_stack+0xfa/0x151 should_fail.cold+0x5/0xa should_failslab+0x5/0x10 __kmalloc+0x72/0x3f0 tracepoint_add_func+0x378/0x990 tracepoint_probe_register+0x9c/0xe0 net_dm_cmd_trace+0x7fc/0x1220 genl_family_rcv_msg_doit+0x228/0x320 genl_rcv_msg+0x328/0x580 netlink_rcv_skb+0x153/0x420 genl_rcv+0x24/0x40 netlink_unicast+0x533/0x7d0 netlink_sendmsg+0x856/0xd90 sock_sendmsg+0xcf/0x120 ____sys_sendmsg+0x6e8/0x810 ___sys_sendmsg+0xf3/0x170 __sys_sendmsg+0xe5/0x1b0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xae
Fixes: 70c69274f354 ("drop_monitor: Initialize timer and work item upon tracing enable") Fixes: 8ee2267ad33e ("drop_monitor: Convert to using devlink tracepoint") Reported-by: syzbot+779559d6503f3a56213d@syzkaller.appspotmail.com Signed-off-by: Ido Schimmel idosch@nvidia.com Reviewed-by: Jiri Pirko jiri@nvidia.com Signed-off-by: David S. Miller davem@davemloft.net --- net/core/drop_monitor.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index 571f191c06d9..db65ce62b625 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -1053,6 +1053,20 @@ static int net_dm_hw_monitor_start(struct netlink_ext_ack *extack) return 0;
err_module_put: + for_each_possible_cpu(cpu) { + struct per_cpu_dm_data *hw_data = &per_cpu(dm_hw_cpu_data, cpu); + struct sk_buff *skb; + + del_timer_sync(&hw_data->send_timer); + cancel_work_sync(&hw_data->dm_alert_work); + while ((skb = __skb_dequeue(&hw_data->drop_queue))) { + struct devlink_trap_metadata *hw_metadata; + + hw_metadata = NET_DM_SKB_CB(skb)->hw_metadata; + net_dm_hw_metadata_free(hw_metadata); + consume_skb(skb); + } + } module_put(THIS_MODULE); return rc; } @@ -1134,6 +1148,15 @@ static int net_dm_trace_on_set(struct netlink_ext_ack *extack) err_unregister_trace: unregister_trace_kfree_skb(ops->kfree_skb_probe, NULL); err_module_put: + for_each_possible_cpu(cpu) { + struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu); + struct sk_buff *skb; + + del_timer_sync(&data->send_timer); + cancel_work_sync(&data->dm_alert_work); + while ((skb = __skb_dequeue(&data->drop_queue))) + consume_skb(skb); + } module_put(THIS_MODULE); return rc; }