The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 5d3c4c79384af06e3c8e25b7770b6247496b4417 Mon Sep 17 00:00:00 2001
From: Sean Christopherson seanjc@google.com Date: Mon, 12 Apr 2021 15:20:49 -0700 Subject: [PATCH] KVM: Stop looking for coalesced MMIO zones if the bus is destroyed
Abort the walk of coalesced MMIO zones if kvm_io_bus_unregister_dev() fails to allocate memory for the new instance of the bus. If it can't instantiate a new bus, unregister_dev() destroys all devices _except_ the target device. But, it doesn't tell the caller that it obliterated the bus and invoked the destructor for all devices that were on the bus. In the coalesced MMIO case, this can result in a deleted list entry dereference due to attempting to continue iterating on coalesced_zones after future entries (in the walk) have been deleted.
Opportunistically add curly braces to the for-loop, which encompasses many lines but sneaks by without braces due to the guts being a single if statement.
Fixes: f65886606c2d ("KVM: fix memory leak in kvm_io_bus_unregister_dev()") Cc: stable@vger.kernel.org Reported-by: Hao Sun sunhao.th@gmail.com Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20210412222050.876100-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d17e3ff1138d..82b066db37cb 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -192,8 +192,8 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr, int len, void *val); int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len, struct kvm_io_device *dev); -void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, - struct kvm_io_device *dev); +int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, + struct kvm_io_device *dev); struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr);
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c index 62bd908ecd58..f08f5e82460b 100644 --- a/virt/kvm/coalesced_mmio.c +++ b/virt/kvm/coalesced_mmio.c @@ -174,21 +174,36 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm, struct kvm_coalesced_mmio_zone *zone) { struct kvm_coalesced_mmio_dev *dev, *tmp; + int r;
if (zone->pio != 1 && zone->pio != 0) return -EINVAL;
mutex_lock(&kvm->slots_lock);
- list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) + list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) { if (zone->pio == dev->zone.pio && coalesced_mmio_in_range(dev, zone->addr, zone->size)) { - kvm_io_bus_unregister_dev(kvm, + r = kvm_io_bus_unregister_dev(kvm, zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev); kvm_iodevice_destructor(&dev->dev); + + /* + * On failure, unregister destroys all devices on the + * bus _except_ the target device, i.e. coalesced_zones + * has been modified. No need to restart the walk as + * there aren't any zones left. + */ + if (r) + break; } + }
mutex_unlock(&kvm->slots_lock);
+ /* + * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's + * perspective, the coalesced MMIO is most definitely unregistered. + */ return 0; } diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index c771d40737c9..f84b126c32d6 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4621,15 +4621,15 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, }
/* Caller must hold slots_lock. */ -void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, - struct kvm_io_device *dev) +int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, + struct kvm_io_device *dev) { int i, j; struct kvm_io_bus *new_bus, *bus;
bus = kvm_get_bus(kvm, bus_idx); if (!bus) - return; + return 0;
for (i = 0; i < bus->dev_count; i++) if (bus->range[i].dev == dev) { @@ -4637,7 +4637,7 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, }
if (i == bus->dev_count) - return; + return 0;
new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1), GFP_KERNEL_ACCOUNT); @@ -4662,7 +4662,7 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, }
kfree(bus); - return; + return new_bus ? 0 : -ENOMEM; }
struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx,