linux-kernel - [RFC PATCH 16/39] KVM: guest_memfd: Add page alignment check for hugetlb guest

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Message-ID: <6f6b891d693ea0733f4b2737858af914bd70a8b6.1726009989.git.ackerleytng@google.com>
Date: Tue, 10 Sep 2024 23:43:47 +0000
From: Ackerley Tng <ackerleytng@...gle.com>
To: tabba@...gle.com, quic_eberman@...cinc.com, roypat@...zon.co.uk, 
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Subject: [RFC PATCH 16/39] KVM: guest_memfd: Add page alignment check for
 hugetlb guest_memfd

When a hugetlb guest_memfd is requested, the requested size should be
aligned to the size of the hugetlb page requested.

Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
---
 virt/kvm/guest_memfd.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 2e6f12e2bac8..eacbfdb950d1 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -909,6 +909,13 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
 	return err;
 }
 
+static inline bool kvm_gmem_hugetlb_page_aligned(u32 flags, u64 value)
+{
+	int page_size_log = (flags >> KVM_GUEST_MEMFD_HUGE_SHIFT) & KVM_GUEST_MEMFD_HUGE_MASK;
+	u64 page_size = 1ULL << page_size_log;
+	return IS_ALIGNED(value, page_size);
+}
+
 #define KVM_GUEST_MEMFD_ALL_FLAGS KVM_GUEST_MEMFD_HUGETLB
 
 int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)
@@ -921,12 +928,18 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)
 		if (flags & ~(KVM_GUEST_MEMFD_ALL_FLAGS |
 			      (KVM_GUEST_MEMFD_HUGE_MASK << KVM_GUEST_MEMFD_HUGE_SHIFT)))
 			return -EINVAL;
+
+		if (!kvm_gmem_hugetlb_page_aligned(flags, size))
+			return -EINVAL;
 	} else {
 		if (flags & ~KVM_GUEST_MEMFD_ALL_FLAGS)
 			return -EINVAL;
+
+		if (!PAGE_ALIGNED(size))
+			return -EINVAL;
 	}
 
-	if (size <= 0 || !PAGE_ALIGNED(size))
+	if (size <= 0)
 		return -EINVAL;
 
 	return __kvm_gmem_create(kvm, size, flags);
-- 
2.46.0.598.g6f2099f65c-goog