2016-11-17 17:21:52

by Paolo Bonzini

Subject: [PATCH] KVM: x86: fix missed SRCU usage in kvm_lapic_set_vapic_addr

Reported by syzkaller:

[ INFO: suspicious RCU usage. ]
4.9.0-rc4+ #47 Not tainted
-------------------------------
./include/linux/kvm_host.h:536 suspicious rcu_dereference_check() usage!

stack backtrace:
CPU: 1 PID: 6679 Comm: syz-executor Not tainted 4.9.0-rc4+ #47
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
ffff880039e2f6d0 ffffffff81c2e46b ffff88003e3a5b40 0000000000000000
0000000000000001 ffffffff83215600 ffff880039e2f700 ffffffff81334ea9
ffffc9000730b000 0000000000000004 ffff88003c4f8420 ffff88003d3f8000
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff81c2e46b>] dump_stack+0xb3/0x118 lib/dump_stack.c:51
[<ffffffff81334ea9>] lockdep_rcu_suspicious+0x139/0x180 kernel/locking/lockdep.c:4445
[< inline >] __kvm_memslots include/linux/kvm_host.h:534
[< inline >] kvm_memslots include/linux/kvm_host.h:541
[<ffffffff8105d6ae>] kvm_gfn_to_hva_cache_init+0xa1e/0xce0 virt/kvm/kvm_main.c:1941
[<ffffffff8112685d>] kvm_lapic_set_vapic_addr+0xed/0x140 arch/x86/kvm/lapic.c:2217

Reported-by: Dmitry Vyukov <[email protected]>
Fixes: fda4e2e85589191b123d31cdc21fd33ee70f50fd
Cc: Andrew Honig <[email protected]>
Cc: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
---
arch/x86/kvm/x86.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3320804bb2ac..04c5d96b1d67 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3431,6 +3431,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
};
case KVM_SET_VAPIC_ADDR: {
struct kvm_vapic_addr va;
+ int idx;

r = -EINVAL;
if (!lapic_in_kernel(vcpu))
@@ -3438,7 +3439,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&va, argp, sizeof va))
goto out;
+ idx = srcu_read_lock(&vcpu->kvm->srcu);
r = kvm_lapic_set_vapic_addr(vcpu, va.vapic_addr);
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
break;
}
case KVM_X86_SETUP_MCE: {
--
1.8.3.1

2016-11-17 17:38:11

by David Hildenbrand

Subject: Re: [PATCH] KVM: x86: fix missed SRCU usage in kvm_lapic_set_vapic_addr

Am 17.11.2016 um 15:55 schrieb Paolo Bonzini:
> Reported by syzkaller:
>
> [ INFO: suspicious RCU usage. ]
> 4.9.0-rc4+ #47 Not tainted
> -------------------------------
> ./include/linux/kvm_host.h:536 suspicious rcu_dereference_check() usage!
>
> stack backtrace:
> CPU: 1 PID: 6679 Comm: syz-executor Not tainted 4.9.0-rc4+ #47
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> ffff880039e2f6d0 ffffffff81c2e46b ffff88003e3a5b40 0000000000000000
> 0000000000000001 ffffffff83215600 ffff880039e2f700 ffffffff81334ea9
> ffffc9000730b000 0000000000000004 ffff88003c4f8420 ffff88003d3f8000
> Call Trace:
> [< inline >] __dump_stack lib/dump_stack.c:15
> [<ffffffff81c2e46b>] dump_stack+0xb3/0x118 lib/dump_stack.c:51
> [<ffffffff81334ea9>] lockdep_rcu_suspicious+0x139/0x180 kernel/locking/lockdep.c:4445
> [< inline >] __kvm_memslots include/linux/kvm_host.h:534
> [< inline >] kvm_memslots include/linux/kvm_host.h:541
> [<ffffffff8105d6ae>] kvm_gfn_to_hva_cache_init+0xa1e/0xce0 virt/kvm/kvm_main.c:1941
> [<ffffffff8112685d>] kvm_lapic_set_vapic_addr+0xed/0x140 arch/x86/kvm/lapic.c:2217
>
> Reported-by: Dmitry Vyukov <[email protected]>
> Fixes: fda4e2e85589191b123d31cdc21fd33ee70f50fd
> Cc: Andrew Honig <[email protected]>
> Cc: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>

Looks good to me!

Reviewed-by: David Hildenbrand <[email protected]>

--

David

2016-11-19 19:31:29

by Radim Krčmář

Subject: Re: [PATCH] KVM: x86: fix missed SRCU usage in kvm_lapic_set_vapic_addr

2016-11-17 15:55+0100, Paolo Bonzini:
> Reported by syzkaller:
>
> [ INFO: suspicious RCU usage. ]
> 4.9.0-rc4+ #47 Not tainted
> -------------------------------
> ./include/linux/kvm_host.h:536 suspicious rcu_dereference_check() usage!
>
> stack backtrace:
> CPU: 1 PID: 6679 Comm: syz-executor Not tainted 4.9.0-rc4+ #47
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> ffff880039e2f6d0 ffffffff81c2e46b ffff88003e3a5b40 0000000000000000
> 0000000000000001 ffffffff83215600 ffff880039e2f700 ffffffff81334ea9
> ffffc9000730b000 0000000000000004 ffff88003c4f8420 ffff88003d3f8000
> Call Trace:
> [< inline >] __dump_stack lib/dump_stack.c:15
> [<ffffffff81c2e46b>] dump_stack+0xb3/0x118 lib/dump_stack.c:51
> [<ffffffff81334ea9>] lockdep_rcu_suspicious+0x139/0x180 kernel/locking/lockdep.c:4445
> [< inline >] __kvm_memslots include/linux/kvm_host.h:534
> [< inline >] kvm_memslots include/linux/kvm_host.h:541
> [<ffffffff8105d6ae>] kvm_gfn_to_hva_cache_init+0xa1e/0xce0 virt/kvm/kvm_main.c:1941
> [<ffffffff8112685d>] kvm_lapic_set_vapic_addr+0xed/0x140 arch/x86/kvm/lapic.c:2217
>
> Reported-by: Dmitry Vyukov <[email protected]>
> Fixes: fda4e2e85589191b123d31cdc21fd33ee70f50fd
> Cc: Andrew Honig <[email protected]>
> Cc: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>
> ---

Applied to kvm/master, thanks.