Re: [PATCH tip] perf/events/core: fix race in bpf program unregister
On Tue, May 19, 2015 at 10:27:05PM -0700, Alexei Starovoitov wrote:
> On 5/15/15 12:15 PM, Alexei Starovoitov wrote:
> >there is a race between perf_event_free_bpf_prog() and free_trace_kprobe():
> >
> >__free_event()
> > event->destroy(event)
> > tp_perf_event_destroy()
> > perf_trace_destroy()
> > perf_trace_event_unreg()
> >
> >which is dropping event->tp_event->perf_refcount and allows to proceed in:
> >
> >unregister_trace_kprobe()
> > unregister_kprobe_event()
> > trace_remove_event_call()
> > probe_remove_event_call()
> >free_trace_kprobe()
> >
> >while __free_event does:
> >call_rcu(>rcu_head, free_event_rcu);
> > free_event_rcu()
> > perf_event_free_bpf_prog()
> >
> >To fix the race simply move perf_event_free_bpf_prog() before
> >event->destroy(), since event->tp_event is still valid at that point.
> >
> >Note, perf_trace_destroy() is not racing with trace_remove_event_call()
> >since they both grab event_mutex.
> >
> >Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to
> >kprobes")
> >Reported-by: Wang Nan
> >Signed-off-by: Alexei Starovoitov
>
> ping.
> This is needed in 4.1.
Thanks, queued for perf/urgent.
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Re: [PATCH tip] perf/events/core: fix race in bpf program unregister
On Tue, May 19, 2015 at 10:27:05PM -0700, Alexei Starovoitov wrote: On 5/15/15 12:15 PM, Alexei Starovoitov wrote: there is a race between perf_event_free_bpf_prog() and free_trace_kprobe(): __free_event() event-destroy(event) tp_perf_event_destroy() perf_trace_destroy() perf_trace_event_unreg() which is dropping event-tp_event-perf_refcount and allows to proceed in: unregister_trace_kprobe() unregister_kprobe_event() trace_remove_event_call() probe_remove_event_call() free_trace_kprobe() while __free_event does: call_rcu(event-rcu_head, free_event_rcu); free_event_rcu() perf_event_free_bpf_prog() To fix the race simply move perf_event_free_bpf_prog() before event-destroy(), since event-tp_event is still valid at that point. Note, perf_trace_destroy() is not racing with trace_remove_event_call() since they both grab event_mutex. Fixes: 2541517c32be (tracing, perf: Implement BPF programs attached to kprobes) Reported-by: Wang Nan wangn...@huawei.com Signed-off-by: Alexei Starovoitov a...@plumgrid.com ping. This is needed in 4.1. Thanks, queued for perf/urgent. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip] perf/events/core: fix race in bpf program unregister
On 5/15/15 12:15 PM, Alexei Starovoitov wrote:
there is a race between perf_event_free_bpf_prog() and free_trace_kprobe():
__free_event()
event->destroy(event)
tp_perf_event_destroy()
perf_trace_destroy()
perf_trace_event_unreg()
which is dropping event->tp_event->perf_refcount and allows to proceed in:
unregister_trace_kprobe()
unregister_kprobe_event()
trace_remove_event_call()
probe_remove_event_call()
free_trace_kprobe()
while __free_event does:
call_rcu(>rcu_head, free_event_rcu);
free_event_rcu()
perf_event_free_bpf_prog()
To fix the race simply move perf_event_free_bpf_prog() before
event->destroy(), since event->tp_event is still valid at that point.
Note, perf_trace_destroy() is not racing with trace_remove_event_call()
since they both grab event_mutex.
Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to
kprobes")
Reported-by: Wang Nan
Signed-off-by: Alexei Starovoitov
ping.
This is needed in 4.1.
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Re: [PATCH tip] perf/events/core: fix race in bpf program unregister
On 5/15/15 12:15 PM, Alexei Starovoitov wrote: there is a race between perf_event_free_bpf_prog() and free_trace_kprobe(): __free_event() event-destroy(event) tp_perf_event_destroy() perf_trace_destroy() perf_trace_event_unreg() which is dropping event-tp_event-perf_refcount and allows to proceed in: unregister_trace_kprobe() unregister_kprobe_event() trace_remove_event_call() probe_remove_event_call() free_trace_kprobe() while __free_event does: call_rcu(event-rcu_head, free_event_rcu); free_event_rcu() perf_event_free_bpf_prog() To fix the race simply move perf_event_free_bpf_prog() before event-destroy(), since event-tp_event is still valid at that point. Note, perf_trace_destroy() is not racing with trace_remove_event_call() since they both grab event_mutex. Fixes: 2541517c32be (tracing, perf: Implement BPF programs attached to kprobes) Reported-by: Wang Nan wangn...@huawei.com Signed-off-by: Alexei Starovoitov a...@plumgrid.com ping. This is needed in 4.1. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH tip] perf/events/core: fix race in bpf program unregister
there is a race between perf_event_free_bpf_prog() and free_trace_kprobe():
__free_event()
event->destroy(event)
tp_perf_event_destroy()
perf_trace_destroy()
perf_trace_event_unreg()
which is dropping event->tp_event->perf_refcount and allows to proceed in:
unregister_trace_kprobe()
unregister_kprobe_event()
trace_remove_event_call()
probe_remove_event_call()
free_trace_kprobe()
while __free_event does:
call_rcu(>rcu_head, free_event_rcu);
free_event_rcu()
perf_event_free_bpf_prog()
To fix the race simply move perf_event_free_bpf_prog() before
event->destroy(), since event->tp_event is still valid at that point.
Note, perf_trace_destroy() is not racing with trace_remove_event_call()
since they both grab event_mutex.
Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to
kprobes")
Reported-by: Wang Nan
Signed-off-by: Alexei Starovoitov
---
Wang, please test the fix to double check.
kernel/events/core.c |3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 84231a146dd5..b27bdc8b3558 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3415,7 +3415,6 @@ static void free_event_rcu(struct rcu_head *head)
if (event->ns)
put_pid_ns(event->ns);
perf_event_free_filter(event);
- perf_event_free_bpf_prog(event);
kfree(event);
}
@@ -3546,6 +3545,8 @@ static void __free_event(struct perf_event *event)
put_callchain_buffers();
}
+ perf_event_free_bpf_prog(event);
+
if (event->destroy)
event->destroy(event);
--
1.7.9.5
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[PATCH tip] perf/events/core: fix race in bpf program unregister
there is a race between perf_event_free_bpf_prog() and free_trace_kprobe(): __free_event() event-destroy(event) tp_perf_event_destroy() perf_trace_destroy() perf_trace_event_unreg() which is dropping event-tp_event-perf_refcount and allows to proceed in: unregister_trace_kprobe() unregister_kprobe_event() trace_remove_event_call() probe_remove_event_call() free_trace_kprobe() while __free_event does: call_rcu(event-rcu_head, free_event_rcu); free_event_rcu() perf_event_free_bpf_prog() To fix the race simply move perf_event_free_bpf_prog() before event-destroy(), since event-tp_event is still valid at that point. Note, perf_trace_destroy() is not racing with trace_remove_event_call() since they both grab event_mutex. Fixes: 2541517c32be (tracing, perf: Implement BPF programs attached to kprobes) Reported-by: Wang Nan wangn...@huawei.com Signed-off-by: Alexei Starovoitov a...@plumgrid.com --- Wang, please test the fix to double check. kernel/events/core.c |3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 84231a146dd5..b27bdc8b3558 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3415,7 +3415,6 @@ static void free_event_rcu(struct rcu_head *head) if (event-ns) put_pid_ns(event-ns); perf_event_free_filter(event); - perf_event_free_bpf_prog(event); kfree(event); } @@ -3546,6 +3545,8 @@ static void __free_event(struct perf_event *event) put_callchain_buffers(); } + perf_event_free_bpf_prog(event); + if (event-destroy) event-destroy(event); -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
