From: Paolo Bonzini Date: Wed, 1 Jun 2016 12:09:21 +0000 (+0200) Subject: KVM: irqfd: fix NULL pointer dereference in kvm_irq_map_gsi X-Git-Tag: Ubuntu-5.2.0-15.16~9037^2~2 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=c622a3c21ede892e370b56e1ceb9eb28f8bbda6b;p=mirror_ubuntu-eoan-kernel.git KVM: irqfd: fix NULL pointer dereference in kvm_irq_map_gsi Found by syzkaller: BUG: unable to handle kernel NULL pointer dereference at 0000000000000120 IP: [] kvm_irq_map_gsi+0x12/0x90 [kvm] PGD 6f80b067 PUD b6535067 PMD 0 Oops: 0000 [#1] SMP CPU: 3 PID: 4988 Comm: a.out Not tainted 4.4.9-300.fc23.x86_64 #1 [...] Call Trace: [] irqfd_update+0x32/0xc0 [kvm] [] kvm_irqfd+0x3dc/0x5b0 [kvm] [] kvm_vm_ioctl+0x164/0x6f0 [kvm] [] do_vfs_ioctl+0x298/0x480 [] SyS_ioctl+0x79/0x90 [] tracesys_phase2+0x84/0x89 Code: b5 71 a7 e0 5b 41 5c 41 5d 5d f3 c3 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 8b 8f 10 2e 00 00 31 c0 48 89 e5 <39> 91 20 01 00 00 76 6a 48 63 d2 48 8b 94 d1 28 01 00 00 48 85 RIP [] kvm_irq_map_gsi+0x12/0x90 [kvm] RSP CR2: 0000000000000120 Testcase: #include #include #include #include #include #include #include long r[26]; int main() { memset(r, -1, sizeof(r)); r[2] = open("/dev/kvm", 0); r[3] = ioctl(r[2], KVM_CREATE_VM, 0); struct kvm_irqfd ifd; ifd.fd = syscall(SYS_eventfd2, 5, 0); ifd.gsi = 3; ifd.flags = 2; ifd.resamplefd = ifd.fd; r[25] = ioctl(r[3], KVM_IRQFD, &ifd); return 0; } Reported-by: Dmitry Vyukov Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c index fe84e1a95dd5..8db197bb6c7a 100644 --- a/virt/kvm/irqchip.c +++ b/virt/kvm/irqchip.c @@ -40,7 +40,7 @@ int kvm_irq_map_gsi(struct kvm *kvm, irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm->irq_srcu, lockdep_is_held(&kvm->irq_lock)); - if (gsi < irq_rt->nr_rt_entries) { + if (irq_rt && gsi < irq_rt->nr_rt_entries) { hlist_for_each_entry(e, &irq_rt->map[gsi], link) { entries[n] = *e; ++n;