linux-kernel - Re: [PATCH linux-next] KVM: x86: don't forget vcpu_put() in kvm_arch_vcpu_ioctl_set

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Date:   Thu, 21 Dec 2017 10:45:54 +0800
From:   Lan Tianyu <tianyu.lan@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Eric Biggers <ebiggers3@...il.com>, kvm@...r.kernel.org
Cc:     rkrcmar@...hat.com, christoffer.dall@...aro.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        Eric Biggers <ebiggers@...gle.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH linux-next] KVM: x86: don't forget vcpu_put() in
 kvm_arch_vcpu_ioctl_set_sregs()

On 2017年12月21日 08:30, Paolo Bonzini wrote:
> On 21/12/2017 01:24, Eric Biggers wrote:
>> From: Eric Biggers <ebiggers@...gle.com>
>>
>> Due to a bad merge resolution between commit f29810335965 ("KVM/x86:
>> Check input paging mode when cs.l is set") and commit b4ef9d4e8cb8
>> ("KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_sregs"),
>> there is a case in kvm_arch_vcpu_ioctl_set_sregs() where vcpu_put() is
>> not called after vcpu_get().  Fix it.
>>
>> Reported-by: syzbot <syzkaller@...glegroups.com>
>> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
>> ---
>>  arch/x86/kvm/x86.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index ea3a98196753..f4e8b5089b28 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -7624,7 +7624,7 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
>>  		goto out;
>>  
>>  	if (kvm_valid_sregs(vcpu, sregs))
>> -		return -EINVAL;
>> +		goto out;
>>  
>>  	apic_base_msr.data = sregs->apic_base;
>>  	apic_base_msr.host_initiated = true;
>>
> 
> Thanks very much Eric, that was fast!  Adding Stephen and the linux-next
> mailing list to Cc.  Adding the kvm/master tree has already paid off.
> 
> Paolo
> 

Hi Paolo:
	Should we check input sregs before loading vcpu? If input sregs is
invalid, the operation is redundant.
-- 
Best regards
Tianyu Lan