On ARM and arm64, we use a dedicated mm_struct to map the UEFI Runtime Services regions, which allows us to map those regions on demand, and in a way that is guaranteed to be compatible with incoming kernels across kexec. As it turns out, we don't fully initialize the mm_struct in the same way as process mm_structs are initialized on fork(), which results in the following crash if CONFIG_CPUMASK_OFFSTACK is enabled: EFI Variables Facility v0.08 2004-May-17 Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = c0204000 [00000000] *pgd=00000000 Internal error: Oops: 805 [#1] SMP ARM Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.6-300.fc25.armv7hl #1 Hardware name: Generic DT based system task: ee90d700 task.stack: ee904000 PC is at __memzero+0x60/0x7c LR is at check_and_switch_context+0x22c/0x494 pc : [<c0515a80>] lr : [<c02234e0>] psr: 000c0093 sp : ee905e18 ip : 00000004 fp : 00000000 r10: 00000000 r9 : c0e8e718 r8 : c0e38f70 r7 : 00000000 r6 : 00000005 r5 : c0e390d8 r4 : c0d87098 r3 : 00000000 r2 : 00000000 r1 : 00000004 r0 : 00000000 Flags: nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5383d Table: 4020406a DAC: 00000051 Process swapper/0 (pid: 1, stack limit = 0xee904220) Stack: (0xee905e18 to 0xee906000) ... [<c0515a80>] (__memzero) from [<c02234e0>] (check_and_switch_context+0x22c/0x494) [<c02234e0>] (check_and_switch_context) from [<c0770cc4>] (virt_efi_get_next_variable+0x28/0x8c) [<c0770cc4>] (virt_efi_get_next_variable) from [<c076dbac>] (efivar_init+0x94/0x2d4) [<c076dbac>] (efivar_init) from [<c076fa38>] (efivars_sysfs_init+0x8c/0x1e8) [<c076fa38>] (efivars_sysfs_init) from [<c0209d48>] (do_one_initcall+0x130/0x158) [<c0209d48>] (do_one_initcall) from [<c0c5bea8>] (kernel_init_freeable+0x210/0x25c) This is due to a missing call to mm_init_cpumask(), so add it. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> --- drivers/firmware/efi/arm-runtime.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c index c394b81fe452..b4dd8b5ad516 100644 --- a/drivers/firmware/efi/arm-runtime.c +++ b/drivers/firmware/efi/arm-runtime.c @@ -45,6 +45,7 @@ static bool __init efi_virtmap_init(void) bool systab_found; efi_mm.pgd = pgd_alloc(&efi_mm); + mm_init_cpumask(&efi_mm); init_new_context(NULL, &efi_mm); systab_found = false; -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
