* [PATCH tip] perf/events/core: fix race in bpf program unregister
@ 2015-05-15 19:15 Alexei Starovoitov
2015-05-20 5:27 ` Alexei Starovoitov
2015-05-27 10:01 ` [tip:perf/core] perf: Fix race in BPF " tip-bot for Alexei Starovoitov
0 siblings, 2 replies; 4+ messages in thread
From: Alexei Starovoitov @ 2015-05-15 19:15 UTC (permalink / raw)
To: Ingo Molnar
Cc: Peter Zijlstra, Arnaldo Carvalho de Melo, Wang Nan, lizefan,
pi3orama, linux-kernel
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 <wangnan0@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH tip] perf/events/core: fix race in bpf program unregister
2015-05-15 19:15 [PATCH tip] perf/events/core: fix race in bpf program unregister Alexei Starovoitov
@ 2015-05-20 5:27 ` Alexei Starovoitov
2015-05-20 6:58 ` Peter Zijlstra
2015-05-27 10:01 ` [tip:perf/core] perf: Fix race in BPF " tip-bot for Alexei Starovoitov
1 sibling, 1 reply; 4+ messages in thread
From: Alexei Starovoitov @ 2015-05-20 5:27 UTC (permalink / raw)
To: Ingo Molnar
Cc: Peter Zijlstra, Arnaldo Carvalho de Melo, Wang Nan, lizefan,
pi3orama, linux-kernel
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 <wangnan0@huawei.com>
> Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
ping.
This is needed in 4.1.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH tip] perf/events/core: fix race in bpf program unregister
2015-05-20 5:27 ` Alexei Starovoitov
@ 2015-05-20 6:58 ` Peter Zijlstra
0 siblings, 0 replies; 4+ messages in thread
From: Peter Zijlstra @ 2015-05-20 6:58 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: Ingo Molnar, Arnaldo Carvalho de Melo, Wang Nan, lizefan,
pi3orama, linux-kernel
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 <wangnan0@huawei.com>
> >Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
>
> ping.
> This is needed in 4.1.
Thanks, queued for perf/urgent.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip:perf/core] perf: Fix race in BPF program unregister
2015-05-15 19:15 [PATCH tip] perf/events/core: fix race in bpf program unregister Alexei Starovoitov
2015-05-20 5:27 ` Alexei Starovoitov
@ 2015-05-27 10:01 ` tip-bot for Alexei Starovoitov
1 sibling, 0 replies; 4+ messages in thread
From: tip-bot for Alexei Starovoitov @ 2015-05-27 10:01 UTC (permalink / raw)
To: linux-tip-commits
Cc: acme, torvalds, linux-kernel, hpa, tglx, peterz, ast, wangnan0, mingo
Commit-ID: dead9f29ddcc69551f35529a252d2704047870d3
Gitweb: http://git.kernel.org/tip/dead9f29ddcc69551f35529a252d2704047870d3
Author: Alexei Starovoitov <ast@plumgrid.com>
AuthorDate: Fri, 15 May 2015 12:15:21 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 27 May 2015 08:46:15 +0200
perf: 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.
Reported-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: lizefan@huawei.com
Cc: pi3orama@163.com
Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes")
Link: http://lkml.kernel.org/r/1431717321-28772-1-git-send-email-ast@plumgrid.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 1a3bf48..eddf1ed 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3442,7 +3442,6 @@ 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);
}
@@ -3573,6 +3572,8 @@ static void __free_event(struct perf_event *event)
put_callchain_buffers();
}
+ perf_event_free_bpf_prog(event);
+
if (event->destroy)
event->destroy(event);
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2015-05-15 19:15 [PATCH tip] perf/events/core: fix race in bpf program unregister Alexei Starovoitov
2015-05-20 5:27 ` Alexei Starovoitov
2015-05-20 6:58 ` Peter Zijlstra
2015-05-27 10:01 ` [tip:perf/core] perf: Fix race in BPF " tip-bot for Alexei Starovoitov
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