From: Sasha Levin <sasha.levin@xxxxxxxxxx> commit db0865543739b3edb2ee9bf340380cf4986b58ff upstream. Commit "x86/nmi: Perform a safe NMI stack trace on all CPUs" has introduced a cpumask_var_t variable: +static cpumask_var_t printtrace_mask; But never allocated it before using it, which caused a NULL ptr deref when trying to print the stack trace: [ 1110.296154] BUG: unable to handle kernel NULL pointer dereference at (null) [ 1110.296169] IP: __memcpy (arch/x86/lib/memcpy_64.S:151) [ 1110.296178] PGD 4c34b3067 PUD 4c351b067 PMD 0 [ 1110.296186] Oops: 0002 [#1] PREEMPT SMP KASAN [ 1110.296234] Dumping ftrace buffer: [ 1110.296330] (ftrace buffer empty) [ 1110.296339] Modules linked in: [ 1110.296345] CPU: 1 PID: 10538 Comm: trinity-c99 Not tainted 3.18.0-rc5-next-20141124-sasha-00058-ge2a8c09-dirty #1499 [ 1110.296348] task: ffff880152650000 ti: ffff8804c3560000 task.ti: ffff8804c3560000 [ 1110.296357] RIP: __memcpy (arch/x86/lib/memcpy_64.S:151) [ 1110.296360] RSP: 0000:ffff8804c3563870 EFLAGS: 00010246 [ 1110.296363] RAX: 0000000000000000 RBX: ffffe8fff3c4a809 RCX: 0000000000000000 [ 1110.296366] RDX: 0000000000000008 RSI: ffffffff9e254040 RDI: 0000000000000000 [ 1110.296369] RBP: ffff8804c3563908 R08: 0000000000ffffff R09: 0000000000ffffff [ 1110.296371] R10: 0000000000000000 R11: 0000000000000006 R12: 0000000000000000 [ 1110.296375] R13: 0000000000000000 R14: ffffffff9e254040 R15: ffffe8fff3c4a809 [ 1110.296379] FS: 00007f9e43b0b700(0000) GS:ffff880107e00000(0000) knlGS:0000000000000000 [ 1110.296382] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 1110.296385] CR2: 0000000000000000 CR3: 00000004e4334000 CR4: 00000000000006a0 [ 1110.296400] Stack: [ 1110.296406] ffffffff81b1e46c 0000000000000000 ffff880107e03fb8 000000000000000b [ 1110.296413] ffff880107dfffc0 ffff880107e03fc0 0000000000000008 ffffffff93f2e9c8 [ 1110.296419] 0000000000000000 ffffda0020fc07f7 0000000000000008 ffff8804c3563901 [ 1110.296420] Call Trace: [ 1110.296429] ? memcpy (mm/kasan/kasan.c:275) [ 1110.296437] ? arch_trigger_all_cpu_backtrace (include/linux/bitmap.h:215 include/linux/cpumask.h:506 arch/x86/kernel/apic/hw_nmi.c:76) [ 1110.296444] arch_trigger_all_cpu_backtrace (include/linux/bitmap.h:215 include/linux/cpumask.h:506 arch/x86/kernel/apic/hw_nmi.c:76) [ 1110.296451] ? dump_stack (./arch/x86/include/asm/preempt.h:95 lib/dump_stack.c:55) [ 1110.296458] do_raw_spin_lock (./arch/x86/include/asm/spinlock.h:86 kernel/locking/spinlock_debug.c:130 kernel/locking/spinlock_debug.c:137) [ 1110.296468] _raw_spin_lock (include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:151) [ 1110.296474] ? __page_check_address (include/linux/spinlock.h:309 mm/rmap.c:630) [ 1110.296481] __page_check_address (include/linux/spinlock.h:309 mm/rmap.c:630) [ 1110.296487] ? preempt_count_sub (kernel/sched/core.c:2615) [ 1110.296493] try_to_unmap_one (include/linux/rmap.h:202 mm/rmap.c:1146) [ 1110.296504] ? anon_vma_interval_tree_iter_next (mm/interval_tree.c:72 mm/interval_tree.c:103) [ 1110.296514] rmap_walk (mm/rmap.c:1653 mm/rmap.c:1725) [ 1110.296521] ? page_get_anon_vma (include/linux/rcupdate.h:423 include/linux/rcupdate.h:935 mm/rmap.c:435) [ 1110.296530] try_to_unmap (mm/rmap.c:1545) [ 1110.296536] ? page_get_anon_vma (mm/rmap.c:437) [ 1110.296545] ? try_to_unmap_nonlinear (mm/rmap.c:1138) [ 1110.296551] ? SyS_msync (mm/rmap.c:1501) [ 1110.296558] ? page_remove_rmap (mm/rmap.c:1409) [ 1110.296565] ? page_get_anon_vma (mm/rmap.c:448) [ 1110.296571] ? anon_vma_ctor (mm/rmap.c:1496) [ 1110.296579] migrate_pages (mm/migrate.c:913 mm/migrate.c:956 mm/migrate.c:1136) [ 1110.296586] ? _raw_spin_unlock_irq (./arch/x86/include/asm/preempt.h:95 include/linux/spinlock_api_smp.h:169 kernel/locking/spinlock.c:199) [ 1110.296593] ? buffer_migrate_lock_buffers (mm/migrate.c:1584) [ 1110.296601] ? handle_mm_fault (mm/memory.c:3163 mm/memory.c:3223 mm/memory.c:3336 mm/memory.c:3365) [ 1110.296607] migrate_misplaced_page (mm/migrate.c:1738) [ 1110.296614] handle_mm_fault (mm/memory.c:3170 mm/memory.c:3223 mm/memory.c:3336 mm/memory.c:3365) [ 1110.296623] __do_page_fault (arch/x86/mm/fault.c:1246) [ 1110.296630] ? vtime_account_user (kernel/sched/cputime.c:701) [ 1110.296638] ? get_parent_ip (kernel/sched/core.c:2559) [ 1110.296646] ? context_tracking_user_exit (kernel/context_tracking.c:144) [ 1110.296656] trace_do_page_fault (arch/x86/mm/fault.c:1329 include/linux/jump_label.h:114 include/linux/context_tracking_state.h:27 include/linux/context_tracking.h:45 arch/x86/mm/fault.c:1330) [ 1110.296664] do_async_page_fault (arch/x86/kernel/kvm.c:280) [ 1110.296670] async_page_fault (arch/x86/kernel/entry_64.S:1285) [ 1110.296755] Code: 08 4c 8b 54 16 f0 4c 8b 5c 16 f8 4c 89 07 4c 89 4f 08 4c 89 54 17 f0 4c 89 5c 17 f8 c3 90 83 fa 08 72 1b 4c 8b 06 4c 8b 4c 16 f8 <4c> 89 07 4c 89 4c 17 f8 c3 66 2e 0f 1f 84 00 00 00 00 00 83 fa All code ======== 0: 08 4c 8b 54 or %cl,0x54(%rbx,%rcx,4) 4: 16 (bad) 5: f0 4c 8b 5c 16 f8 lock mov -0x8(%rsi,%rdx,1),%r11 b: 4c 89 07 mov %r8,(%rdi) e: 4c 89 4f 08 mov %r9,0x8(%rdi) 12: 4c 89 54 17 f0 mov %r10,-0x10(%rdi,%rdx,1) 17: 4c 89 5c 17 f8 mov %r11,-0x8(%rdi,%rdx,1) 1c: c3 retq 1d: 90 nop 1e: 83 fa 08 cmp $0x8,%edx 21: 72 1b jb 0x3e 23: 4c 8b 06 mov (%rsi),%r8 26: 4c 8b 4c 16 f8 mov -0x8(%rsi,%rdx,1),%r9 2b:* 4c 89 07 mov %r8,(%rdi) <-- trapping instruction 2e: 4c 89 4c 17 f8 mov %r9,-0x8(%rdi,%rdx,1) 33: c3 retq 34: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1) 3b: 00 00 00 3e: 83 fa 00 cmp $0x0,%edx Code starting with the faulting instruction =========================================== 0: 4c 89 07 mov %r8,(%rdi) 3: 4c 89 4c 17 f8 mov %r9,-0x8(%rdi,%rdx,1) 8: c3 retq 9: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1) 10: 00 00 00 13: 83 fa 00 cmp $0x0,%edx [ 1110.296760] RIP __memcpy (arch/x86/lib/memcpy_64.S:151) [ 1110.296763] RSP <ffff8804c3563870> [ 1110.296765] CR2: 0000000000000000 Link: http://lkml.kernel.org/r/1416931560-10603-1-git-send-email-sasha.levin@xxxxxxxxxx Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx> [wanglong: backport to 3.10 stable - adjust context ] Signed-off-by: Wang Long <long.wanglong@xxxxxxxxxx> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> --- arch/x86/kernel/apic/hw_nmi.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index 1eb5f90..c168e8a 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -30,7 +30,7 @@ u64 hw_nmi_get_sample_period(int watchdog_thresh) #ifdef arch_trigger_all_cpu_backtrace /* For reliability, we're prepared to waste bits here. */ static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; -static cpumask_var_t printtrace_mask; +static cpumask_t printtrace_mask; #define NMI_BUF_SIZE 4096 @@ -67,7 +67,7 @@ void arch_trigger_all_cpu_backtrace(void) return; cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); - cpumask_copy(printtrace_mask, to_cpumask(backtrace_mask)); + cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask)); /* * Set up per_cpu seq_buf buffers that the NMIs running on the other * CPUs will write to. @@ -91,7 +91,7 @@ void arch_trigger_all_cpu_backtrace(void) * Now that all the NMIs have triggered, we can dump out their * back traces safely to the console. */ - for_each_cpu(cpu, printtrace_mask) { + for_each_cpu(cpu, &printtrace_mask) { int last_i = 0; s = &per_cpu(nmi_print_seq, cpu); -- 1.8.3.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html