From: Athira Rajeev atrajeev@linux.vnet.ibm.com
commit 60b7ed54a41b550d50caf7f2418db4a7e75b5bdc upstream.
On systems without any specific PMU driver support registered, running perf record causes Oops.
The relevant portion from call trace:
BUG: Kernel NULL pointer dereference on read at 0x00000040 Faulting instruction address: 0xc0021f0c Oops: Kernel access of bad area, sig: 11 [#1] BE PAGE_SIZE=4K PREEMPT CMPCPRO SAF3000 DIE NOTIFICATION CPU: 0 PID: 442 Comm: null_syscall Not tainted 5.13.0-rc6-s3k-dev-01645-g7649ee3d2957 #5164 NIP: c0021f0c LR: c00e8ad8 CTR: c00d8a5c NIP perf_instruction_pointer+0x10/0x60 LR perf_prepare_sample+0x344/0x674 Call Trace: perf_prepare_sample+0x7c/0x674 (unreliable) perf_event_output_forward+0x3c/0x94 __perf_event_overflow+0x74/0x14c perf_swevent_hrtimer+0xf8/0x170 __hrtimer_run_queues.constprop.0+0x160/0x318 hrtimer_interrupt+0x148/0x3b0 timer_interrupt+0xc4/0x22c Decrementer_virt+0xb8/0xbc
During perf record session, perf_instruction_pointer() is called to capture the sample IP. This function in core-book3s accesses ppmu->flags. If a platform specific PMU driver is not registered, ppmu is set to NULL and accessing its members results in a crash. Fix this crash by checking if ppmu is set.
Fixes: 2ca13a4cc56c ("powerpc/perf: Use regs->nip when SIAR is zero") Cc: stable@vger.kernel.org # v5.11+ Reported-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Athira Rajeev atrajeev@linux.vnet.ibm.com Tested-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/1623952506-1431-1-git-send-email-atrajeev@linux.vn... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/perf/core-book3s.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -2242,7 +2242,7 @@ unsigned long perf_instruction_pointer(s bool use_siar = regs_use_siar(regs); unsigned long siar = mfspr(SPRN_SIAR);
- if (ppmu->flags & PPMU_P10_DD1) { + if (ppmu && (ppmu->flags & PPMU_P10_DD1)) { if (siar) return siar; else