[tip:perf/core] perf: Disallow user-space stack dumps for function trace events

[tip-bot for Jiri Olsa]

Commit-ID:  63c45f4ba533e9749da16298db53e491c25d805b
Gitweb:     http://git.kernel.org/tip/63c45f4ba533e9749da16298db53e491c25d805b
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Sun, 2 Mar 2014 16:56:39 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 11 Mar 2014 11:57:58 +0100

perf: Disallow user-space stack dumps for function trace events

Recent issues with user space callchains processing within
page fault handler tracing showed as Peter said 'there's
just too much fail surface'.

The user space stack dump is just another source of the this issue.

Related list discussions:
  http://marc.info/?t=139302086500001&r=1&w=2
  http://marc.info/?t=139301437300003&r=1&w=2

Suggested-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1393775800-13524-3-git-send-email-jolsa@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/trace/trace_event_perf.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index d5e01c3..c894614 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -42,6 +42,13 @@ static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
 		 */
 		if (!p_event->attr.exclude_callchain_user)
 			return -EINVAL;
+
+		/*
+		 * Same reason to disable user stack dump as for user space
+		 * callchains above.
+		 */
+		if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
+			return -EINVAL;
 	}
 
 	/* No tracing, just counting, so no obvious leak */
--
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