From: Sean Christopherson seanjc@google.com
mainline inclusion from mainline-v5.13-rc1 commit 5d3c4c79384af06e3c8e25b7770b6247496b4417 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I94VOT CVE: CVE-2021-47060
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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 Signed-off-by: Zheng Yejian zhengyejian1@huawei.com --- include/linux/kvm_host.h | 4 ++-- virt/kvm/coalesced_mmio.c | 19 +++++++++++++++++-- virt/kvm/kvm_main.c | 10 +++++----- 3 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index cac0fad2695f..6346d0123077 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -195,8 +195,8 @@ 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 b9336693c87e..70bd2dbdfffe 100644 --- a/virt/kvm/coalesced_mmio.c +++ b/virt/kvm/coalesced_mmio.c @@ -172,16 +172,31 @@ 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;
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 (coalesced_mmio_in_range(dev, zone->addr, zone->size)) { - kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &dev->dev); + r = kvm_io_bus_unregister_dev(kvm, 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 5f4f222c991f..62cd5624b715 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3853,15 +3853,15 @@ 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) { @@ -3869,7 +3869,7 @@ 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(sizeof(*bus) + ((bus->dev_count - 1) * sizeof(struct kvm_io_range)), GFP_KERNEL); @@ -3890,7 +3890,7 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, rcu_assign_pointer(kvm->buses[bus_idx], new_bus); synchronize_srcu_expedited(&kvm->srcu); 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,