diff options
| author | Christian Borntraeger | 2023-05-15 10:42:34 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2023-07-19 16:21:57 +0200 |
| commit | 86bfb18bad60fc468e5f112cbbd918462a8dd435 (patch) | |
| tree | c4b576aec3c8a05b34e49e7ec99c6a4bb18f5590 | |
| parent | c78ad1060ce98e1c09b7964c254850962806ebde (diff) | |
KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler
[ 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>
| -rw-r--r-- | arch/s390/kvm/diag.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c index 807fa9da1e72..3c65b8258ae6 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); |