[PATCH] KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation

[Hyunwoo Kim]

inject_abt64() rewalks the guest stage-1 page tables via
__kvm_find_s1_desc_level() when injecting an abort for a failed S1PTW, and
__kvm_at_s12() calls kvm_walk_nested_s2() to perform the stage-2
translation. Both walks reference kvm->memslots through kvm_read_guest(),
which reads the descriptors, and __kvm_at_swap_desc(), which updates the
access flag, so they must run while holding the kvm->srcu read lock.
__kvm_at_swap_desc() asserts srcu_read_lock_held() on entry, and the other
callers of these walks, handle_at_slow(), kvm_translate_vncr() and
kvm_handle_guest_abort(), take the lock before calling them.

inject_abt64() is reached from the SEA and size fault injection paths,
which run before kvm_handle_guest_abort() takes the lock, and
__kvm_at_s12() does not hold the lock across the stage-2 walk. Take the
kvm->srcu read lock with guard(srcu) in both places so that it is held for
the duration of the walk.

Cc: stable at vger.kernel.org
Fixes: 50f77dc87f13 ("KVM: arm64: Populate level on S1PTW SEA injection")
Fixes: be04cebf3e78 ("KVM: arm64: nv: Add emulation of AT S12E{0,1}{R,W}")
Signed-off-by: Hyunwoo Kim <imv4bel at gmail.com>
---
 arch/arm64/kvm/at.c           | 3 +++
 arch/arm64/kvm/inject_fault.c | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 9f8f0ae8e86e..eb334a1c2672 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -1569,6 +1569,9 @@ int __kvm_at_s12(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
 	/* Do the stage-2 translation */
 	ipa = (par & GENMASK_ULL(47, 12)) | (vaddr & GENMASK_ULL(11, 0));
 	out.esr = 0;
+
+	guard(srcu)(&vcpu->kvm->srcu);
+
 	ret = kvm_walk_nested_s2(vcpu, ipa, &out);
 	if (ret < 0)
 		return ret;
diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 89982bd3345f..868895ed0930 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -121,6 +121,8 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
 		if (hpfar == INVALID_GPA)
 			return;
 
+		guard(srcu)(&vcpu->kvm->srcu);
+
 		ret = __kvm_find_s1_desc_level(vcpu, addr, hpfar, &level);
 		if (ret)
 			return;
-- 
2.43.0