From eefd6b06b17c5478e7c24bea6f64beaa2c431ca6 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Tue, 15 Sep 2015 14:41:56 +0800 Subject: kvm: fix double free for fast mmio eventfd We register wildcard mmio eventfd on two buses, once for KVM_MMIO_BUS and once on KVM_FAST_MMIO_BUS but with a single iodev instance. This will lead to an issue: kvm_io_bus_destroy() knows nothing about the devices on two buses pointing to a single dev. Which will lead to double free[1] during exit. Fix this by allocating two instances of iodevs then registering one on KVM_MMIO_BUS and another on KVM_FAST_MMIO_BUS. CPU: 1 PID: 2894 Comm: qemu-system-x86 Not tainted 3.19.0-26-generic #28-Ubuntu Hardware name: LENOVO 2356BG6/2356BG6, BIOS G7ET96WW (2.56 ) 09/12/2013 task: ffff88009ae0c4b0 ti: ffff88020e7f0000 task.ti: ffff88020e7f0000 RIP: 0010:[] [] ioeventfd_release+0x28/0x60 [kvm] RSP: 0018:ffff88020e7f3bc8 EFLAGS: 00010292 RAX: dead000000200200 RBX: ffff8801ec19c900 RCX: 000000018200016d RDX: ffff8801ec19cf80 RSI: ffffea0008bf1d40 RDI: ffff8801ec19c900 RBP: ffff88020e7f3bd8 R08: 000000002fc75a01 R09: 000000018200016d R10: ffffffffc07df6ae R11: ffff88022fc75a98 R12: ffff88021e7cc000 R13: ffff88021e7cca48 R14: ffff88021e7cca50 R15: ffff8801ec19c880 FS: 00007fc1ee3e6700(0000) GS:ffff88023e240000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8f389d8000 CR3: 000000023dc13000 CR4: 00000000001427e0 Stack: ffff88021e7cc000 0000000000000000 ffff88020e7f3be8 ffffffffc07e2622 ffff88020e7f3c38 ffffffffc07df69a ffff880232524160 ffff88020e792d80 0000000000000000 ffff880219b78c00 0000000000000008 ffff8802321686a8 Call Trace: [] ioeventfd_destructor+0x12/0x20 [kvm] [] kvm_put_kvm+0xca/0x210 [kvm] [] kvm_vcpu_release+0x18/0x20 [kvm] [] __fput+0xe7/0x250 [] ____fput+0xe/0x10 [] task_work_run+0xd4/0xf0 [] do_exit+0x368/0xa50 [] ? recalc_sigpending+0x1f/0x60 [] do_group_exit+0x45/0xb0 [] get_signal+0x291/0x750 [] do_signal+0x28/0xab0 [] ? do_futex+0xdb/0x5d0 [] ? __wake_up_locked_key+0x18/0x20 [] ? SyS_futex+0x76/0x170 [] do_notify_resume+0x69/0xb0 [] int_signal+0x12/0x17 Code: 5d c3 90 0f 1f 44 00 00 55 48 89 e5 53 48 89 fb 48 83 ec 08 48 8b 7f 20 e8 06 d6 a5 c0 48 8b 43 08 48 8b 13 48 89 df 48 89 42 08 <48> 89 10 48 b8 00 01 10 00 00 RIP [] ioeventfd_release+0x28/0x60 [kvm] RSP Cc: stable@vger.kernel.org Cc: Gleb Natapov Cc: Paolo Bonzini Signed-off-by: Jason Wang Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini --- virt/kvm/eventfd.c | 43 +++++++++++++++++++++++++------------------ 1 file changed, 25 insertions(+), 18 deletions(-) (limited to 'virt') diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 0829c7f197a0..79db45336e3a 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -817,16 +817,6 @@ static int kvm_assign_ioeventfd_idx(struct kvm *kvm, if (ret < 0) goto unlock_fail; - /* When length is ignored, MMIO is also put on a separate bus, for - * faster lookups. - */ - if (!args->len && bus_idx == KVM_MMIO_BUS) { - ret = kvm_io_bus_register_dev(kvm, KVM_FAST_MMIO_BUS, - p->addr, 0, &p->dev); - if (ret < 0) - goto register_fail; - } - kvm->buses[bus_idx]->ioeventfd_count++; list_add_tail(&p->list, &kvm->ioeventfds); @@ -834,8 +824,6 @@ static int kvm_assign_ioeventfd_idx(struct kvm *kvm, return 0; -register_fail: - kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev); unlock_fail: mutex_unlock(&kvm->slots_lock); @@ -874,10 +862,6 @@ kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx, continue; kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev); - if (!p->length && p->bus_idx == KVM_MMIO_BUS) { - kvm_io_bus_unregister_dev(kvm, KVM_FAST_MMIO_BUS, - &p->dev); - } kvm->buses[bus_idx]->ioeventfd_count--; ioeventfd_release(p); ret = 0; @@ -894,14 +878,19 @@ kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx, static int kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) { enum kvm_bus bus_idx = ioeventfd_bus_from_flags(args->flags); + int ret = kvm_deassign_ioeventfd_idx(kvm, bus_idx, args); + + if (!args->len && bus_idx == KVM_MMIO_BUS) + kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args); - return kvm_deassign_ioeventfd_idx(kvm, bus_idx, args); + return ret; } static int kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) { enum kvm_bus bus_idx; + int ret; bus_idx = ioeventfd_bus_from_flags(args->flags); /* must be natural-word sized, or 0 to ignore length */ @@ -930,7 +919,25 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) KVM_IOEVENTFD_FLAG_DATAMATCH)) return -EINVAL; - return kvm_assign_ioeventfd_idx(kvm, bus_idx, args); + ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args); + if (ret) + goto fail; + + /* When length is ignored, MMIO is also put on a separate bus, for + * faster lookups. + */ + if (!args->len && bus_idx == KVM_MMIO_BUS) { + ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args); + if (ret < 0) + goto fast_fail; + } + + return 0; + +fast_fail: + kvm_deassign_ioeventfd_idx(kvm, bus_idx, args); +fail: + return ret; } int -- cgit v1.2.3-70-g09d2