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

PATCH In review Hyunwoo Kim 2 participants 2 messages Jun 3

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Stable branch arm64 KVM arm64
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Hyunwoo Kim

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#0 lore raw

PATCH v2 1/1 KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation

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 [email protected]
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 <[email protected]>
Signed-off-by Hyunwoo Kim <[email protected]>

---
Changes in v2:
- Wrap only the walker calls with scoped_guard() and move the injection lock into __kvm_find_s1_desc_level(), as suggested by Oliver.
- Reword the commit message as suggested.
- v1: https://lore.kernel.org/all/ah7_BAAzHggzdZeI@v4bel/

---
 arch/arm64/kvm/at.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
arch/arm64/kvm/at.c +4 -2
index 9f8f0ae8e86e..889c2c15d7bd 100644
@@ -1569,7 +1569,8 @@ 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;
-	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 ret;
 

@@ -1665,7 +1666,8 @@ int __kvm_find_s1_desc_level(struct kvm_vcpu *vcpu, u64 va, u64 ipa, int *level)
 	}
 
 	/* Walk the guest's PT, looking for a match along the way */
-	ret = walk_s1(vcpu, &wi, &wr, va);
+	scoped_guard(srcu, &vcpu->kvm->srcu)
+		ret = walk_s1(vcpu, &wi, &wr, va);
 	switch (ret) {
 	case -EINTR:
 		/* We interrupted the walk on a match, return the level */
Signature · 1 line
2.43.0
maintainer Reviewed-by on v2 1/1
#1 lore raw
Quoted 5 lines · Hyunwoo Kim

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.

Quoted 7 lines

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

Cc [email protected]
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 <[email protected]>
Signed-off-by Hyunwoo Kim <[email protected]>
Reviewed-by Oliver Upton <[email protected]>
Signature · 2 lines
Thanks,
Oliver