[PATCH 6.12.y] KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation

[Hyunwoo Kim <imv4bel@gmail.com>]

[ Upstream commit f2ca45b50d4216c9cc7ffabf50d9ad1932209251 ]

walk_s1() and kvm_walk_nested_s2() expect to be called while holding
kvm->srcu to guard against memslot changes. While this is generally
the case, __kvm_at_s12() and __kvm_find_s1_desc_level() call into the
respective walkers without taking kvm->srcu.

Fix by acquiring kvm->srcu prior to the table walk in both instances.

Cc: stable@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}")
Suggested-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Reviewed-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/aiAZfdeyanIvP8SD@v4bel
Signed-off-by: Marc Zyngier <maz@kernel.org>
[ Hyunwoo Kim: __kvm_at_s12() returns void in 6.12.y, so the context
  differs from upstream (return; instead of return ret;). The
  __kvm_find_s1_desc_level() hunk (Fixes: 50f77dc87f13) is dropped, as
  that function is v6.18+ and absent here; only the __kvm_at_s12() /
  kvm_walk_nested_s2() change (Fixes: be04cebf3e78) applies. ]
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
 arch/arm64/kvm/at.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 39f0e87a340e..8192bc0bbc87 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -1087,7 +1087,8 @@ void __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;
-	ret = kvm_walk_nested_s2(vcpu, ipa, &out);
+	scoped_guard(srcu, &vcpu->kvm->srcu)
+		ret = kvm_walk_nested_s2(vcpu, ipa, &out);
 	if (ret < 0)
 		return;
 
-- 
2.43.0