[PATCH v2 4/5] KVM: SNP: Fix kunmap_local() unmapping order

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@xxxxxxxxxx>

Mappings created with kmap_local_page() or kmap_local_pfn() must be
unmapped in the reverse order they were acquired, following a LIFO
(last-in, first-out) stack-based approach.

In sev_gmem_post_populate(), src_vaddr is mapped first and dst_vaddr is
mapped second. The current code incorrectly calls kunmap_local() for
src_vaddr before dst_vaddr.

Swap the kunmap_local() calls to ensure the mappings are released in the
correct order.

Fixes: 2a62345b3052 ("KVM: guest_memfd: GUP source pages prior to populating guest memory")
Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 2f254c447923e..dbf75326a40f4 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2360,8 +2360,8 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 
 		memcpy(dst_vaddr, src_vaddr, PAGE_SIZE);
 
-		kunmap_local(src_vaddr);
 		kunmap_local(dst_vaddr);
+		kunmap_local(src_vaddr);
 	}
 
 	ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, PG_LEVEL_4K,
@@ -2396,8 +2396,8 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
 
 		memcpy(src_vaddr, dst_vaddr, PAGE_SIZE);
 
-		kunmap_local(src_vaddr);
 		kunmap_local(dst_vaddr);
+		kunmap_local(src_vaddr);
 	}
 
 out:

-- 
2.54.0.794.g4f17f83d09-goog