From: Christian Borntraeger borntraeger@linux.ibm.com
[ Upstream commit 0bc380beb78aa352eadbc21d934dd9606fcee808 ]
We do check for target CPU == -1, but this might change at the time we are going to use it. Hold the physical target CPU in a local variable to avoid out-of-bound accesses to the cpu arrays.
Cc: Pierre Morel pmorel@linux.ibm.com Fixes: 87e28a15c42c ("KVM: s390: diag9c (directed yield) forwarding") Reported-by: Marc Hartmayer mhartmay@linux.ibm.com Reviewed-by: Nico Boehr nrb@linux.ibm.com Reviewed-by: Pierre Morel pmorel@linux.ibm.com Signed-off-by: Christian Borntraeger borntraeger@linux.ibm.com Signed-off-by: Janosch Frank frankja@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kvm/diag.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c index 807fa9da1e721..3c65b8258ae67 100644 --- a/arch/s390/kvm/diag.c +++ b/arch/s390/kvm/diag.c @@ -166,6 +166,7 @@ static int diag9c_forwarding_overrun(void) static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu) { struct kvm_vcpu *tcpu; + int tcpu_cpu; int tid;
tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4]; @@ -181,14 +182,15 @@ static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu) goto no_yield;
/* target guest VCPU already running */ - if (READ_ONCE(tcpu->cpu) >= 0) { + tcpu_cpu = READ_ONCE(tcpu->cpu); + if (tcpu_cpu >= 0) { if (!diag9c_forwarding_hz || diag9c_forwarding_overrun()) goto no_yield;
/* target host CPU already running */ - if (!vcpu_is_preempted(tcpu->cpu)) + if (!vcpu_is_preempted(tcpu_cpu)) goto no_yield; - smp_yield_cpu(tcpu->cpu); + smp_yield_cpu(tcpu_cpu); VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: yield forwarded", tid);