| Message ID | 20161123202548.29324-1-rkrcmar@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 23/11/2016 21:25, Radim Krčmář wrote: > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c > index 25810b144b58..ddd63b8b176e 100644 > --- a/arch/x86/kvm/irq_comm.c > +++ b/arch/x86/kvm/irq_comm.c > @@ -41,6 +41,15 @@ static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e, > bool line_status) > { > struct kvm_pic *pic = pic_irqchip(kvm); > + > + /* > + * XXX: rejecting pic routes when pic isn't in use would be better, > + * but the default routing table is installed while kvm->arch.vpic is > + * NULL and KVM_CREATE_IRQCHIP can race with KVM_SET_GSI_ROUTING. > + */ > + if (!pic) > + return -1; > + > return kvm_pic_set_irq(pic, e->irqchip.pin, irq_source_id, level); > } > Can you explain the race with the default routing table better? It seems to me that it can only make the routing table go from invalid to valid (there is no KVM_DESTROY_IRQCHIP) so it's benign. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c index 25810b144b58..ddd63b8b176e 100644 --- a/arch/x86/kvm/irq_comm.c +++ b/arch/x86/kvm/irq_comm.c @@ -41,6 +41,15 @@ static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e, bool line_status) { struct kvm_pic *pic = pic_irqchip(kvm); + + /* + * XXX: rejecting pic routes when pic isn't in use would be better, + * but the default routing table is installed while kvm->arch.vpic is + * NULL and KVM_CREATE_IRQCHIP can race with KVM_SET_GSI_ROUTING. + */ + if (!pic) + return -1; + return kvm_pic_set_irq(pic, e->irqchip.pin, irq_source_id, level); } @@ -49,6 +58,10 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e, bool line_status) { struct kvm_ioapic *ioapic = kvm->arch.vioapic; + + if (!ioapic) + return -1; + return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, irq_source_id, level, line_status); }
Split irqchip allows pic and ioapic routes to be used without them being created, which results in NULL access. Check for NULL and avoid it. (The setup is too racy for a nicer solutions.) Found by syzkaller: general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 3 PID: 11923 Comm: kworker/3:2 Not tainted 4.9.0-rc5+ #27 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: events irqfd_inject task: ffff88006a06c7c0 task.stack: ffff880068638000 RIP: 0010:[...] [...] __lock_acquire+0xb35/0x3380 kernel/locking/lockdep.c:3221 RSP: 0000:ffff88006863ea20 EFLAGS: 00010006 RAX: dffffc0000000000 RBX: dffffc0000000000 RCX: 0000000000000000 RDX: 0000000000000039 RSI: 0000000000000000 RDI: 1ffff1000d0c7d9e RBP: ffff88006863ef58 R08: 0000000000000001 R09: 0000000000000000 R10: 00000000000001c8 R11: 0000000000000000 R12: ffff88006a06c7c0 R13: 0000000000000001 R14: ffffffff8baab1a0 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88006d100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004abdd0 CR3: 000000003e2f2000 CR4: 00000000000026e0 Stack: ffffffff894d0098 1ffff1000d0c7d56 ffff88006863ecd0 dffffc0000000000 ffff88006a06c7c0 0000000000000000 ffff88006863ecf8 0000000000000082 0000000000000000 ffffffff815dd7c1 ffffffff00000000 ffffffff00000000 Call Trace: [...] lock_acquire+0x2a2/0x790 kernel/locking/lockdep.c:3746 [...] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [...] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151 [...] spin_lock include/linux/spinlock.h:302 [...] kvm_ioapic_set_irq+0x4c/0x100 arch/x86/kvm/ioapic.c:379 [...] kvm_set_ioapic_irq+0x8f/0xc0 arch/x86/kvm/irq_comm.c:52 [...] kvm_set_irq+0x239/0x640 arch/x86/kvm/../../../virt/kvm/irqchip.c:101 [...] irqfd_inject+0xb4/0x150 arch/x86/kvm/../../../virt/kvm/eventfd.c:60 [...] process_one_work+0xb40/0x1ba0 kernel/workqueue.c:2096 [...] worker_thread+0x214/0x18a0 kernel/workqueue.c:2230 [...] kthread+0x328/0x3e0 kernel/kthread.c:209 [...] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433 Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: stable@vger.kernel.org Fixes: 49df6397edfc ("KVM: x86: Split the APIC from the rest of IRQCHIP.") Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> --- Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Steve Rutherford <srutherford@google.com> --- arch/x86/kvm/irq_comm.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)