One path in power_pmu_event_init() calls get_cpu_var(), but is
missing matching call to put_cpu_var(), which causes preemption
imbalance and crash in user-space:
Page fault in user mode with in_atomic() = 1 mm = c000001fefa5a280
NIP = 3fff9bf2cae0 MSR = 900000014280f032
Oops: Weird page fault, sig: 11 [#23]
SMP NR_CPUS=2048 NUMA PowerNV
Modules linked in: <snip>
CPU: 43 PID: 10285 Comm: a.out Tainted: G D 4.0.0-rc5+ #1
task: c000001fe82c9200 ti: c000001fe835c000 task.ti: c000001fe835c000
NIP: 00003fff9bf2cae0 LR: 00003fff9bee4898 CTR: 00003fff9bf2cae0
REGS: c000001fe835fea0 TRAP: 0401 Tainted: G D (4.0.0-rc5+)
MSR: 900000014280f032 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI> CR: 22000028
XER: 00000000
CFAR: 00003fff9bee4894 SOFTE: 1
GPR00: 00003fff9bee494c 00003fffe01c2ee0 00003fff9c084410 0000000010020068
GPR04: 0000000000000000 0000000000000002 0000000000000008 0000000000000001
GPR08: 0000000000000001 00003fff9c074a30 00003fff9bf2cae0 00003fff9bf2cd70
GPR12: 0000000052000022 00003fff9c10b700
NIP [00003fff9bf2cae0] 0x3fff9bf2cae0
LR [00003fff9bee4898] 0x3fff9bee4898
Call Trace:
---[ end trace 5d3d952b5d4185d4 ]---
BUG: sleeping function called from invalid context at
kernel/locking/rwsem.c:41
in_atomic(): 1, irqs_disabled(): 0, pid: 10285, name: a.out
INFO: lockdep is turned off.
CPU: 43 PID: 10285 Comm: a.out Tainted: G D 4.0.0-rc5+ #1
Call Trace:
[c000001fe835f990] [c00000000089c014] .dump_stack+0x98/0xd4 (unreliable)
[c000001fe835fa10] [c0000000000e4138] .___might_sleep+0x1d8/0x2e0
[c000001fe835faa0] [c000000000888da8] .down_read+0x38/0x110
[c000001fe835fb30] [c0000000000bf2f4] .exit_signals+0x24/0x160
[c000001fe835fbc0] [c0000000000abde0] .do_exit+0xd0/0xe70
[c000001fe835fcb0] [c00000000001f4c4] .die+0x304/0x450
[c000001fe835fd60] [c00000000088e1f4] .do_page_fault+0x2d4/0x900
[c000001fe835fe30] [c000000000008664] handle_page_fault+0x10/0x30
note: a.out[10285] exited with preempt_count 1
Reproducer:
#include <stdio.h>
#include <unistd.h>
#include <syscall.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
static struct perf_event_attr event = {
.type = PERF_TYPE_RAW,
.size = sizeof(struct perf_event_attr),
.sample_type = PERF_SAMPLE_BRANCH_STACK,
.branch_sample_type = PERF_SAMPLE_BRANCH_ANY_RETURN,
};
int main()
{
syscall(__NR_perf_event_open, &event, 0, -1, -1, 0);
}
Signed-off-by: Jan Stancek <jstan...@redhat.com>
---
arch/powerpc/perf/core-book3s.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 7c4f669..b101c0b 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1832,8 +1832,10 @@ static int power_pmu_event_init(struct perf_event *event)
cpuhw->bhrb_filter = ppmu->bhrb_filter_map(
event->attr.branch_sample_type);
- if(cpuhw->bhrb_filter == -1)
+ if (cpuhw->bhrb_filter == -1) {
+ put_cpu_var(cpu_hw_events);
return -EOPNOTSUPP;
+ }
}
put_cpu_var(cpu_hw_events);
--
1.7.1
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