Found by syzkaller:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000120
IP: [<ffffffffa0797202>] kvm_irq_map_gsi+0x12/0x90 [kvm]
PGD 6f80b067 PUD b6535067 PMD 0
Oops: 0000 [#1] SMP
CPU: 3 PID: 4988 Comm: a.out Not tainted 4.4.9-300.fc23.x86_64 #1
[...]
Call Trace:
[<ffffffffa0795f62>] irqfd_update+0x32/0xc0 [kvm]
[<ffffffffa0796c7c>] kvm_irqfd+0x3dc/0x5b0 [kvm]
[<ffffffffa07943f4>] kvm_vm_ioctl+0x164/0x6f0 [kvm]
[<ffffffff81241648>] do_vfs_ioctl+0x298/0x480
[<ffffffff812418a9>] SyS_ioctl+0x79/0x90
[<ffffffff817a1062>] tracesys_phase2+0x84/0x89
Code: b5 71 a7 e0 5b 41 5c 41 5d 5d f3 c3 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 8b 8f 10 2e 00 00 31 c0 48 89 e5 <39> 91 20 01 00 00 76 6a 48 63 d2 48 8b 94 d1 28 01 00 00 48 85
RIP [<ffffffffa0797202>] kvm_irq_map_gsi+0x12/0x90 [kvm]
RSP <ffff8800926cbca8>
CR2: 0000000000000120
Testcase:
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdint.h>
#include <linux/kvm.h>
#include <fcntl.h>
#include <sys/ioctl.h>
long r[26];
int main()
{
memset(r, -1, sizeof(r));
r[2] = open("/dev/kvm", 0);
r[3] = ioctl(r[2], KVM_CREATE_VM, 0);
struct kvm_irqfd ifd;
ifd.fd = syscall(SYS_eventfd2, 5, 0);
ifd.gsi = 3;
ifd.flags = 2;
ifd.resamplefd = ifd.fd;
r[25] = ioctl(r[3], KVM_IRQFD, &ifd);
return 0;
}
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
virt/kvm/irqchip.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
index fe84e1a95dd5..8db197bb6c7a 100644
--- a/virt/kvm/irqchip.c
+++ b/virt/kvm/irqchip.c
@@ -40,7 +40,7 @@ int kvm_irq_map_gsi(struct kvm *kvm,
irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm->irq_srcu,
lockdep_is_held(&kvm->irq_lock));
- if (gsi < irq_rt->nr_rt_entries) {
+ if (irq_rt && gsi < irq_rt->nr_rt_entries) {
hlist_for_each_entry(e, &irq_rt->map[gsi], link) {
entries[n] = *e;
++n;
--
1.8.3.1
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