From: Nicholas Piggin npiggin@gmail.com
[ Upstream commit e7bde88cdb4f0e432398a7d29ca2a15d2c18952a ]
The OPAL IMC driver's shutdown handler disables nest PMU counters by walking nodes and taking the first CPU out of their cpumask, which is used to index into the paca (get_hard_smp_processor_id()). This does not always do the right thing, and in particular for CPU-less nodes it returns NR_CPUS and that overruns the paca and dereferences random memory.
Fix it by being more careful about checking returned CPU, and only using online CPUs. It's not clear this shutdown code makes sense after commit 885dcd709b ("powerpc/perf: Add nest IMC PMU support"), but this should not make things worse
Currently the bug causes us to call OPAL with a junk CPU number. A separate patch in development to change the way pacas are allocated escalates this bug into a crash:
Unable to handle kernel paging request for data at address 0x2a21af1eeb000076 Faulting instruction address: 0xc0000000000a5468 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP opal_imc_counters_shutdown+0x148/0x1d0 LR opal_imc_counters_shutdown+0x134/0x1d0 Call Trace: opal_imc_counters_shutdown+0x134/0x1d0 (unreliable) platform_drv_shutdown+0x44/0x60 device_shutdown+0x1f8/0x350 kernel_restart_prepare+0x54/0x70 kernel_restart+0x28/0xc0 SyS_reboot+0x1d0/0x2c0 system_call+0x58/0x6c
Signed-off-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- arch/powerpc/platforms/powernv/opal-imc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c index 465ea105b771..5f27854b57aa 100644 --- a/arch/powerpc/platforms/powernv/opal-imc.c +++ b/arch/powerpc/platforms/powernv/opal-imc.c @@ -126,9 +126,11 @@ static void disable_nest_pmu_counters(void) const struct cpumask *l_cpumask;
get_online_cpus(); - for_each_online_node(nid) { + for_each_node_with_cpus(nid) { l_cpumask = cpumask_of_node(nid); - cpu = cpumask_first(l_cpumask); + cpu = cpumask_first_and(l_cpumask, cpu_online_mask); + if (cpu >= nr_cpu_ids) + continue; opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST, get_hard_smp_processor_id(cpu)); }