4.9-stable review patch. If anyone has any objections, please let me know.
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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.linutr... 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 @@ -578,7 +578,7 @@ 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; @@ -601,6 +601,10 @@ fail: return 0; }
+ if (WARN_ON_ONCE(!event)) + goto fail; + + hwc = &event->hw; msr = hwc->config_base; buf = ibs_data.regs; rdmsrl(msr, *buf);