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Date: Fri, 11 Sep 2015 11:17:35 +0800
From: Jason Wang <jasowang@...hat.com>
To: gleb@...nel.org, pbonzini@...hat.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: mst@...hat.com, cornelia.huck@...ibm.com,
Jason Wang <jasowang@...hat.com>
Subject: [PATCH V4 2/4] kvm: fix double free for fast mmio eventfd
We register wildcard mmio eventfd on two buses, one for KVM_MMIO_BUS
and another is KVM_FAST_MMIO_BUS but with a single iodev
instance. This will lead an issue: kvm_io_bus_destroy() knows nothing
about the devices on two buses points to a single dev. Which will lead
double free[1] during exit. Fixing this by using allocate two
instances of iodevs then register 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:[<ffffffffc07e25d8>] [<ffffffffc07e25d8>] 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:
[<ffffffffc07e2622>] ioeventfd_destructor+0x12/0x20 [kvm]
[<ffffffffc07df69a>] kvm_put_kvm+0xca/0x210 [kvm]
[<ffffffffc07df818>] kvm_vcpu_release+0x18/0x20 [kvm]
[<ffffffff811f69f7>] __fput+0xe7/0x250
[<ffffffff811f6bae>] ____fput+0xe/0x10
[<ffffffff81093f04>] task_work_run+0xd4/0xf0
[<ffffffff81079358>] do_exit+0x368/0xa50
[<ffffffff81082c8f>] ? recalc_sigpending+0x1f/0x60
[<ffffffff81079ad5>] do_group_exit+0x45/0xb0
[<ffffffff81085c71>] get_signal+0x291/0x750
[<ffffffff810144d8>] do_signal+0x28/0xab0
[<ffffffff810f3a3b>] ? do_futex+0xdb/0x5d0
[<ffffffff810b7028>] ? __wake_up_locked_key+0x18/0x20
[<ffffffff810f3fa6>] ? SyS_futex+0x76/0x170
[<ffffffff81014fc9>] do_notify_resume+0x69/0xb0
[<ffffffff817cb9af>] 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 [<ffffffffc07e25d8>] ioeventfd_release+0x28/0x60 [kvm]
RSP <ffff88020e7f3bc8>
Cc: Gleb Natapov <gleb@...nel.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
virt/kvm/eventfd.c | 111 ++++++++++++++++++++++++++++-------------------------
1 file changed, 59 insertions(+), 52 deletions(-)
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 163258d..1a023ac 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 && !(args->flags & KVM_IOEVENTFD_FLAG_PIO)) {
- 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);
@@ -847,41 +835,6 @@ fail:
}
static int
-kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
-{
- enum kvm_bus bus_idx;
-
- bus_idx = ioeventfd_bus_from_flags(args->flags);
- /* must be natural-word sized, or 0 to ignore length */
- switch (args->len) {
- case 0:
- case 1:
- case 2:
- case 4:
- case 8:
- break;
- default:
- return -EINVAL;
- }
-
- /* check for range overflow */
- if (args->addr + args->len < args->addr)
- return -EINVAL;
-
- /* check for extra flags that we don't understand */
- if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
- return -EINVAL;
-
- /* ioeventfd with no length can't be combined with DATAMATCH */
- if (!args->len &&
- args->flags & (KVM_IOEVENTFD_FLAG_PIO |
- KVM_IOEVENTFD_FLAG_DATAMATCH))
- return -EINVAL;
-
- return kvm_assign_ioeventfd_idx(kvm, bus_idx, args);
-}
-
-static int
kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
struct kvm_ioeventfd *args)
{
@@ -909,10 +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) {
- kvm_io_bus_unregister_dev(kvm, KVM_FAST_MMIO_BUS,
- &p->dev);
- }
kvm->buses[bus_idx]->ioeventfd_count--;
ioeventfd_release(p);
ret = 0;
@@ -929,8 +878,66 @@ 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)
+ kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
+
+ return ret;
+}
- return kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
+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 */
+ switch (args->len) {
+ case 0:
+ case 1:
+ case 2:
+ case 4:
+ case 8:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* check for range overflow */
+ if (args->addr + args->len < args->addr)
+ return -EINVAL;
+
+ /* check for extra flags that we don't understand */
+ if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
+ return -EINVAL;
+
+ /* ioeventfd with no length can't be combined with DATAMATCH */
+ if (!args->len &&
+ args->flags & (KVM_IOEVENTFD_FLAG_PIO |
+ KVM_IOEVENTFD_FLAG_DATAMATCH))
+ return -EINVAL;
+
+ 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 && !(args->flags & KVM_IOEVENTFD_FLAG_PIO)) {
+ ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
+ if (ret < 0)
+ goto fast_fail;
+ }
+
+ return 0;
+
+fast_fail:
+ kvm_deassign_ioeventfd(kvm, args);
+fail:
+ return ret;
}
int
--
2.1.4
--
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