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authorPeter Zijlstra <peterz@infradead.org>2015-05-21 10:57:13 +0200
committerIngo Molnar <mingo@kernel.org>2015-05-27 08:46:44 +0200
commitb371b594317869971af326adcf7cd65cabdb4087 (patch)
treef60f3250212653a52a00ee4b5b36ab7f2e8423da /include/linux/perf_event.h
parentdead9f29ddcc69551f35529a252d2704047870d3 (diff)
perf/x86: Fix event/group validation
Commit 43b4578071c0 ("perf/x86: Reduce stack usage of x86_schedule_events()") violated the rule that 'fake' scheduling; as used for event/group validation; should not change the event state. This went mostly un-noticed because repeated calls of x86_pmu::get_event_constraints() would give the same result. And x86_pmu::put_event_constraints() would mostly not do anything. Commit e979121b1b15 ("perf/x86/intel: Implement cross-HT corruption bug workaround") made the situation much worse by actually setting the event->hw.constraint value to NULL, so when validation and actual scheduling interact we get NULL ptr derefs. Fix it by removing the constraint pointer from the event and move it back to an array, this time in cpuc instead of on the stack. validate_group() x86_schedule_events() event->hw.constraint = c; # store <context switch> perf_task_event_sched_in() ... x86_schedule_events(); event->hw.constraint = c2; # store ... put_event_constraints(event); # assume failure to schedule intel_put_event_constraints() event->hw.constraint = NULL; <context switch end> c = event->hw.constraint; # read -> NULL if (!test_bit(hwc->idx, c->idxmsk)) # <- *BOOM* NULL deref This in particular is possible when the event in question is a cpu-wide event and group-leader, where the validate_group() tries to add an event to the group. Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Hunter <ahh@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 43b4578071c0 ("perf/x86: Reduce stack usage of x86_schedule_events()") Fixes: e979121b1b15 ("perf/x86/intel: Implement cross-HT corruption bug workaround") Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/perf_event.h')
-rw-r--r--include/linux/perf_event.h4
1 files changed, 0 insertions, 4 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 61992cf2e977..d8a82a89f35a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -92,8 +92,6 @@ struct hw_perf_event_extra {
int idx; /* index in shared_regs->regs[] */
};
-struct event_constraint;
-
/**
* struct hw_perf_event - performance event hardware details:
*/
@@ -112,8 +110,6 @@ struct hw_perf_event {
struct hw_perf_event_extra extra_reg;
struct hw_perf_event_extra branch_reg;
-
- struct event_constraint *constraint;
};
struct { /* software */
struct hrtimer hrtimer;