| From foo@baz Sun Aug 26 09:13:00 CEST 2018 |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Fri, 20 Jul 2018 10:39:07 +0200 |
| Subject: perf/x86/amd/ibs: Don't access non-started event |
| |
| From: Thomas Gleixner <tglx@linutronix.de> |
| |
| [ Upstream commit d2753e6b4882a637a0e8fb3b9c2e15f33265300e ] |
| |
| Paul Menzel reported the following bug: |
| |
| > Enabling the undefined behavior sanitizer and building GNU/Linux 4.18-rc5+ |
| > (with some unrelated commits) with GCC 8.1.0 from Debian Sid/unstable, the |
| > warning below is shown. |
| > |
| > > [ 2.111913] |
| > > ================================================================================ |
| > > [ 2.111917] UBSAN: Undefined behaviour in arch/x86/events/amd/ibs.c:582:24 |
| > > [ 2.111919] member access within null pointer of type 'struct perf_event' |
| > > [ 2.111926] CPU: 0 PID: 144 Comm: udevadm Not tainted 4.18.0-rc5-00316-g4864b68cedf2 #104 |
| > > [ 2.111928] Hardware name: ASROCK E350M1/E350M1, BIOS TIMELESS 01/01/1970 |
| > > [ 2.111930] Call Trace: |
| > > [ 2.111943] dump_stack+0x55/0x89 |
| > > [ 2.111949] ubsan_epilogue+0xb/0x33 |
| > > [ 2.111953] handle_null_ptr_deref+0x7f/0x90 |
| > > [ 2.111958] __ubsan_handle_type_mismatch_v1+0x55/0x60 |
| > > [ 2.111964] perf_ibs_handle_irq+0x596/0x620 |
| |
| The code dereferences event before checking the STARTED bit. Patch |
| below should cure the issue. |
| |
| The warning should not trigger, if I analyzed the thing correctly. |
| (And Paul's testing confirms this.) |
| |
| Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> |
| Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> |
| Cc: Arnaldo Carvalho de Melo <acme@redhat.com> |
| Cc: Borislav Petkov <bp@alien8.de> |
| Cc: Jiri Olsa <jolsa@redhat.com> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Paul Menzel <pmenzel+linux-x86@molgen.mpg.de> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Stephane Eranian <eranian@google.com> |
| Cc: Vince Weaver <vincent.weaver@maine.edu> |
| Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1807200958390.1580@nanos.tec.linutronix.de |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/events/amd/ibs.c | 6 +++++- |
| 1 file changed, 5 insertions(+), 1 deletion(-) |
| |
| --- a/arch/x86/events/amd/ibs.c |
| +++ b/arch/x86/events/amd/ibs.c |
| @@ -579,7 +579,7 @@ static int perf_ibs_handle_irq(struct pe |
| { |
| struct cpu_perf_ibs *pcpu = this_cpu_ptr(perf_ibs->pcpu); |
| struct perf_event *event = pcpu->event; |
| - struct hw_perf_event *hwc = &event->hw; |
| + struct hw_perf_event *hwc; |
| struct perf_sample_data data; |
| struct perf_raw_record raw; |
| struct pt_regs regs; |
| @@ -602,6 +602,10 @@ fail: |
| return 0; |
| } |
| |
| + if (WARN_ON_ONCE(!event)) |
| + goto fail; |
| + |
| + hwc = &event->hw; |
| msr = hwc->config_base; |
| buf = ibs_data.regs; |
| rdmsrl(msr, *buf); |