x86/apic/x2apic: Fix a NULL pointer deref when handling a dying cpu
Subsystems (2)
PATCH 1/1 x86/apic/x2apic: Fix a NULL pointer deref when handling a dying cpu
Check that the per-cpu cluster mask pointer has been set prior to clearing a dying cpu's bit. The per-cpu pointer is not set until the target cpu reaches smp_callin() during CPUHP_BRINGUP_CPU, whereas the teardown function, x2apic_dead_cpu(), is associated with the earlier CPUHP_X2APIC_PREPARE. If an error occurs before the cpu is awakened, e.g. if do_boot_cpu() itself fails, x2apic_dead_cpu() will dereference the NULL pointer and cause a panic.
smpboot: do_boot_cpu failed(-22) to wakeup CPU#1
BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP PTI CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.2.0+ #120 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:x2apic_dead_cpu+0x1a/0x30 Code: <f0> 48 0f b3 78 08 31 c0 c3 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 RSP: 0000:ffffc9000001be58 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 RDX: ffff88817bb00000 RSI: 0000000000000027 RDI: 0000000000000001 RBP: 0000000000000027 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000266 R11: 0000000000000002 R12: 0000000000000000 R13: ffffffff81038c00 R14: 00000000fffffffb R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88817ba00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000008 CR3: 000000000500a001 CR4: 0000000000160ef0 Call Trace: cpuhp_invoke_callback+0x9a/0x580 _cpu_up+0x10d/0x140 do_cpu_up+0x69/0xb0 smp_init+0x63/0xa9 kernel_init_freeable+0xd7/0x229 ? rest_init+0xa0/0xa0 kernel_init+0xa/0x100 ret_from_fork+0x35/0x40
---
The do_boot_cpu() -EINVAL failure is due to unrelated code that isn't in mainline, i.e. there is no underlying bug that needs to be investigated.
arch/x86/kernel/apic/x2apic_cluster.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
arch/x86/kernel/apic/x2apic_cluster.c +2 -1
@@ -156,7 +156,8 @@ static int x2apic_dead_cpu(unsigned int dead_cpu) {struct cluster_mask *cmsk =per_cpu (cluster_masks, dead_cpu); -cpumask_clear_cpu (dead_cpu, &cmsk->mask); +if (cmsk) +cpumask_clear_cpu (dead_cpu, &cmsk->mask);free_cpumask_var (per_cpu (ipi_mask, dead_cpu));return 0 ; }
Signature · 1 line
2.22.0
The following commit has been merged into the x86/urgent branch of tip:
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 7a22e03b0c02988e91003c505b34d752a51de344 Gitweb: https://git.kernel.org/tip/7a22e03b0c02988e91003c505b34d752a51de344 Author: Sean Christopherson <[email protected]> AuthorDate: Tue, 01 Oct 2019 13:50:19 -07:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Tue, 15 Oct 2019 10:57:09 +02:00
x86/apic/x2apic: Fix a NULL pointer deref when handling a dying cpu
Check that the per-cpu cluster mask pointer has been set prior to clearing a dying cpu's bit. The per-cpu pointer is not set until the target cpu reaches smp_callin() during CPUHP_BRINGUP_CPU, whereas the teardown function, x2apic_dead_cpu(), is associated with the earlier CPUHP_X2APIC_PREPARE. If an error occurs before the cpu is awakened, e.g. if do_boot_cpu() itself fails, x2apic_dead_cpu() will dereference the NULL pointer and cause a panic.
smpboot: do_boot_cpu failed(-22) to wakeup CPU#1
BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:x2apic_dead_cpu+0x1a/0x30 Call Trace: cpuhp_invoke_callback+0x9a/0x580 _cpu_up+0x10d/0x140 do_cpu_up+0x69/0xb0 smp_init+0x63/0xa9 kernel_init_freeable+0xd7/0x229 ? rest_init+0xa0/0xa0 kernel_init+0xa/0x100 ret_from_fork+0x35/0x40
--- arch/x86/kernel/apic/x2apic_cluster.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
arch/x86/kernel/apic/x2apic_cluster.c +2 -1
@@ -156,7 +156,8 @@ static int x2apic_dead_cpu(unsigned int dead_cpu) {struct cluster_mask *cmsk =per_cpu (cluster_masks, dead_cpu); -cpumask_clear_cpu (dead_cpu, &cmsk->mask); +if (cmsk) +cpumask_clear_cpu (dead_cpu, &cmsk->mask);free_cpumask_var (per_cpu (ipi_mask, dead_cpu));return 0 ; }
The following commit has been merged into the x86/urgent branch of tip:
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 7a22e03b0c02988e91003c505b34d752a51de344 Gitweb: https://git.kernel.org/tip/7a22e03b0c02988e91003c505b34d752a51de344 Author: Sean Christopherson <[email protected]> AuthorDate: Tue, 01 Oct 2019 13:50:19 -07:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Tue, 15 Oct 2019 10:57:09 +02:00
x86/apic/x2apic: Fix a NULL pointer deref when handling a dying cpu
Check that the per-cpu cluster mask pointer has been set prior to clearing a dying cpu's bit. The per-cpu pointer is not set until the target cpu reaches smp_callin() during CPUHP_BRINGUP_CPU, whereas the teardown function, x2apic_dead_cpu(), is associated with the earlier CPUHP_X2APIC_PREPARE. If an error occurs before the cpu is awakened, e.g. if do_boot_cpu() itself fails, x2apic_dead_cpu() will dereference the NULL pointer and cause a panic.
smpboot: do_boot_cpu failed(-22) to wakeup CPU#1
BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:x2apic_dead_cpu+0x1a/0x30 Call Trace: cpuhp_invoke_callback+0x9a/0x580 _cpu_up+0x10d/0x140 do_cpu_up+0x69/0xb0 smp_init+0x63/0xa9 kernel_init_freeable+0xd7/0x229 ? rest_init+0xa0/0xa0 kernel_init+0xa/0x100 ret_from_fork+0x35/0x40
--- arch/x86/kernel/apic/x2apic_cluster.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
arch/x86/kernel/apic/x2apic_cluster.c +2 -1
@@ -156,7 +156,8 @@ static int x2apic_dead_cpu(unsigned int dead_cpu) {struct cluster_mask *cmsk =per_cpu (cluster_masks, dead_cpu); -cpumask_clear_cpu (dead_cpu, &cmsk->mask); +if (cmsk) +cpumask_clear_cpu (dead_cpu, &cmsk->mask);free_cpumask_var (per_cpu (ipi_mask, dead_cpu));return 0 ; }