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KVM: s390: Take srcu when importing watchpoint data

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__import_wp_info() backs up the original guest memory contents of a
watchpoint with read_guest_abs(), which is kvm_read_guest() and therefore
resolves the memslot via __kvm_memslots(). That requires kvm->srcu (or
kvm->slots_lock) to be held, otherwise a concurrent memslot update can
free the memslots array under us once its SRCU grace period has elapsed.

As this is not fast path, following lock ordering (mutex first, then
srcu) take the big hammer and hold the srcu for the full import.

Fixes: 27291e2165 ("KVM: s390: hardware support for guest debugging")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260805110455.7200-7-borntraeger@linux.ibm.com>
This commit is contained in:
Christian Borntraeger 2026-08-05 13:04:53 +02:00 committed by Claudio Imbrenda
parent aa9c8e8baf
commit a4e482def8
1 changed files with 4 additions and 2 deletions
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6
arch/s390/kvm/kvm-s390.c
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@ -4248,8 +4248,10 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
/* enforce guest PER */
kvm_s390_set_cpuflags(vcpu, CPUSTAT_P);
if (dbg->control & KVM_GUESTDBG_USE_HW_BP)
rc = kvm_s390_import_bp_data(vcpu, dbg);
if (dbg->control & KVM_GUESTDBG_USE_HW_BP) {
scoped_guard(srcu, &vcpu->kvm->srcu)
rc = kvm_s390_import_bp_data(vcpu, dbg);
}
} else {
kvm_s390_clear_cpuflags(vcpu, CPUSTAT_P);
vcpu->arch.guestdbg.last_bp = 0;