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Message-Id: <20210310102801.2531062-1-idosch@idosch.org>
Date: Wed, 10 Mar 2021 12:28:01 +0200
From: Ido Schimmel <idosch@...sch.org>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, nhorman@...driver.com,
jiri@...dia.com, mlxsw@...dia.com, Ido Schimmel <idosch@...dia.com>
Subject: [PATCH net] drop_monitor: Perform cleanup upon probe registration failure
From: Ido Schimmel <idosch@...dia.com>
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@...kaller.appspotmail.com
Signed-off-by: Ido Schimmel <idosch@...dia.com>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
---
I asked syzbot to test it yesterday, but didn't get a reply. Anyway, I
managed to reproduce it locally by patching the code and verified the
issue does not reproduce with the fix.
---
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;
}
--
2.29.2
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