This is a note to let you know that I've just added the patch titled
KVM: eventfd: fix NULL deref irqbypass consumer
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-eventfd-fix-null-deref-irqbypass-consumer.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4f3dbdf47e150016aacd734e663347fcaa768303 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Date: Thu, 5 Jan 2017 17:39:42 -0800
Subject: KVM: eventfd: fix NULL deref irqbypass consumer
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From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
commit 4f3dbdf47e150016aacd734e663347fcaa768303 upstream.
Reported syzkaller:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: irq_bypass_unregister_consumer+0x9d/0xb70 [irqbypass]
PGD 0
Oops: 0002 [#1] SMP
CPU: 1 PID: 125 Comm: kworker/1:1 Not tainted 4.9.0+ #1
Workqueue: kvm-irqfd-cleanup irqfd_shutdown [kvm]
task: ffff9bbe0dfbb900 task.stack: ffffb61802014000
RIP: 0010:irq_bypass_unregister_consumer+0x9d/0xb70 [irqbypass]
Call Trace:
irqfd_shutdown+0x66/0xa0 [kvm]
process_one_work+0x16b/0x480
worker_thread+0x4b/0x500
kthread+0x101/0x140
? process_one_work+0x480/0x480
? kthread_create_on_node+0x60/0x60
ret_from_fork+0x25/0x30
RIP: irq_bypass_unregister_consumer+0x9d/0xb70 [irqbypass] RSP: ffffb61802017e20
CR2: 0000000000000008
The syzkaller folks reported a NULL pointer dereference that due to
unregister an consumer which fails registration before. The syzkaller
creates two VMs w/ an equal eventfd occasionally. So the second VM
fails to register an irqbypass consumer. It will make irqfd as inactive
and queue an workqueue work to shutdown irqfd and unregister the irqbypass
consumer when eventfd is closed. However, the second consumer has been
initialized though it fails registration. So the token(same as the first
VM's) is taken to unregister the consumer through the workqueue, the
consumer of the first VM is found and unregistered, then NULL deref incurred
in the path of deleting consumer from the consumers list.
This patch fixes it by making irq_bypass_register/unregister_consumer()
looks for the consumer entry based on consumer pointer itself instead of
token matching.
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Suggested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
virt/lib/irqbypass.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/virt/lib/irqbypass.c
+++ b/virt/lib/irqbypass.c
@@ -195,7 +195,7 @@ int irq_bypass_register_consumer(struct
mutex_lock(&lock);
list_for_each_entry(tmp, &consumers, node) {
- if (tmp->token == consumer->token) {
+ if (tmp->token == consumer->token || tmp == consumer) {
mutex_unlock(&lock);
module_put(THIS_MODULE);
return -EBUSY;
@@ -245,7 +245,7 @@ void irq_bypass_unregister_consumer(stru
mutex_lock(&lock);
list_for_each_entry(tmp, &consumers, node) {
- if (tmp->token != consumer->token)
+ if (tmp != consumer)
continue;
list_for_each_entry(producer, &producers, node) {
Patches currently in stable-queue which might be from wanpeng.li@xxxxxxxxxxx are
queue-4.9/kvm-eventfd-fix-null-deref-irqbypass-consumer.patch
queue-4.9/kvm-x86-fix-null-deref-in-vcpu_scan_ioapic.patch
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