4.17-stable review patch. If anyone has any objections, please let me know.
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From: Anju T Sudhakar anju@linux.vnet.ibm.com
commit d2032678e57fc508d7878307badde8f89b632ba3 upstream.
Currently memory is allocated for core-imc based on cpu_present_mask, which has bit 'cpu' set iff cpu is populated. We use (cpu number / threads per core) as the array index to access the memory.
Under some circumstances firmware marks a CPU as GUARDed CPU and boot the system, until cleared of errors, these CPU's are unavailable for all subsequent boots. GUARDed CPUs are possible but not present from linux view, so it blows a hole when we assume the max length of our allocation is driven by our max present cpus, where as one of the cpus might be online and be beyond the max present cpus, due to the hole. So (cpu number / threads per core) value bounds the array index and leads to memory overflow.
Call trace observed during a guard test:
Faulting instruction address: 0xc000000000149f1c cpu 0x69: Vector: 380 (Data Access Out of Range) at [c000003fea303420] pc:c000000000149f1c: prefetch_freepointer+0x14/0x30 lr:c00000000014e0f8: __kmalloc+0x1a8/0x1ac sp:c000003fea3036a0 msr:9000000000009033 dar:c9c54b2c91dbf6b7 current = 0xc000003fea2c0000 paca = 0xc00000000fddd880 softe: 3 irq_happened: 0x01 pid = 1, comm = swapper/104 Linux version 4.16.7-openpower1 (smc@smc-desktop) (gcc version 6.4.0 (Buildroot 2018.02.1-00006-ga8d1126)) #2 SMP Fri May 4 16:44:54 PDT 2018 enter ? for help call trace: __kmalloc+0x1a8/0x1ac (unreliable) init_imc_pmu+0x7f4/0xbf0 opal_imc_counters_probe+0x3fc/0x43c platform_drv_probe+0x48/0x80 driver_probe_device+0x22c/0x308 __driver_attach+0xa0/0xd8 bus_for_each_dev+0x88/0xb4 driver_attach+0x2c/0x40 bus_add_driver+0x1e8/0x228 driver_register+0xd0/0x114 __platform_driver_register+0x50/0x64 opal_imc_driver_init+0x24/0x38 do_one_initcall+0x150/0x15c kernel_init_freeable+0x250/0x254 kernel_init+0x1c/0x150 ret_from_kernel_thread+0x5c/0xc8
Allocating memory for core-imc based on cpu_possible_mask, which has bit 'cpu' set iff cpu is populatable, will fix this issue.
Reported-by: Pridhiviraj Paidipeddi ppaidipe@linux.vnet.ibm.com Signed-off-by: Anju T Sudhakar anju@linux.vnet.ibm.com Reviewed-by: Balbir Singh bsingharora@gmail.com Tested-by: Pridhiviraj Paidipeddi ppaidipe@linux.vnet.ibm.com Fixes: 39a846db1d57 ("powerpc/perf: Add core IMC PMU support") Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/perf/imc-pmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -1146,7 +1146,7 @@ static int init_nest_pmu_ref(void)
static void cleanup_all_core_imc_memory(void) { - int i, nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core); + int i, nr_cores = DIV_ROUND_UP(num_possible_cpus(), threads_per_core); struct imc_mem_info *ptr = core_imc_pmu->mem_info; int size = core_imc_pmu->counter_mem_size;
@@ -1264,7 +1264,7 @@ static int imc_mem_init(struct imc_pmu * if (!pmu_ptr->pmu.name) return -ENOMEM;
- nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core); + nr_cores = DIV_ROUND_UP(num_possible_cpus(), threads_per_core); pmu_ptr->mem_info = kcalloc(nr_cores, sizeof(struct imc_mem_info), GFP_KERNEL);