3.16.75-rc1 review patch. If anyone has any objections, please let me know.
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From: Jan Stancek jstancek@redhat.com
commit 68de8867ea5d99127e836c23f6bccf4d44859623 upstream.
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 jstancek@redhat.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/powerpc/perf/core-book3s.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -1825,8 +1825,10 @@ static int power_pmu_event_init(struct p 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);