linux-hardening - [RFC PATCH v2 09/19] KVM: x86: Extend kvm_range_has_memory_attributes() with match

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Message-ID: <20231113022326.24388-10-mic@digikod.net>
Date: Sun, 12 Nov 2023 21:23:16 -0500
From: Mickaël Salaün <mic@...ikod.net>
To: Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Wanpeng Li <wanpengli@...cent.com>
Cc: Mickaël Salaün <mic@...ikod.net>,
	Alexander Graf <graf@...zon.com>,
	Chao Peng <chao.p.peng@...ux.intel.com>,
	"Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	Forrest Yuan Yu <yuanyu@...gle.com>,
	James Gowans <jgowans@...zon.com>,
	James Morris <jamorris@...ux.microsoft.com>,
	John Andersen <john.s.andersen@...el.com>,
	"Madhavan T . Venkataraman" <madvenka@...ux.microsoft.com>,
	Marian Rotariu <marian.c.rotariu@...il.com>,
	Mihai Donțu <mdontu@...defender.com>,
	Nicușor Cîțu <nicu.citu@...oud.com>,
	Thara Gopinath <tgopinath@...rosoft.com>,
	Trilok Soni <quic_tsoni@...cinc.com>,
	Wei Liu <wei.liu@...nel.org>,
	Will Deacon <will@...nel.org>,
	Yu Zhang <yu.c.zhang@...ux.intel.com>,
	Zahra Tarkhani <ztarkhani@...rosoft.com>,
	Ștefan Șicleru <ssicleru@...defender.com>,
	dev@...ts.cloudhypervisor.org,
	kvm@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	qemu-devel@...gnu.org,
	virtualization@...ts.linux-foundation.org,
	x86@...nel.org,
	xen-devel@...ts.xenproject.org
Subject: [RFC PATCH v2 09/19] KVM: x86: Extend kvm_range_has_memory_attributes() with match_all

This enables to check if an attribute is tied to any memory page in a
range. This will be useful in a folling commit to check for
KVM_MEMORY_ATTRIBUTE_HEKI_IMMUTABLE.

Cc: Chao Peng <chao.p.peng@...ux.intel.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Yu Zhang <yu.c.zhang@...ux.intel.com>
Signed-off-by: Mickaël Salaün <mic@...ikod.net>
---

Changes since v1:
* New patch
---
 arch/x86/kvm/mmu/mmu.c   |  2 +-
 include/linux/kvm_host.h |  2 +-
 virt/kvm/kvm_main.c      | 27 ++++++++++++++++++---------
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index d7010e09440d..2024ff21d036 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7279,7 +7279,7 @@ static bool hugepage_has_attrs(struct kvm *kvm, struct kvm_memory_slot *slot,
 	const unsigned long end = start + KVM_PAGES_PER_HPAGE(level);
 
 	if (level == PG_LEVEL_2M)
-		return kvm_range_has_memory_attributes(kvm, start, end, attrs);
+		return kvm_range_has_memory_attributes(kvm, start, end, attrs, true);
 
 	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
 		if (hugepage_test_mixed(slot, gfn, level - 1) ||
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index de68390ab0f2..9ecb016a336f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2391,7 +2391,7 @@ static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn
 }
 
 bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-				     unsigned long attrs);
+				     unsigned long attrs, bool match_all);
 bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
 					struct kvm_gfn_range *range);
 bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e2c178db17d5..67dbaaf40c1c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2435,11 +2435,11 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 
 #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
 /*
- * Returns true if _all_ gfns in the range [@start, @end) have attributes
- * matching the @attrs bitmask.
+ * According to @match_all, returns true if _all_ (respectively _any_) gfns in
+ * the range [@start, @end) have attributes matching the @attrs bitmask.
  */
 bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-				     unsigned long attrs)
+				     unsigned long attrs, bool match_all)
 {
 	XA_STATE(xas, &kvm->mem_attr_array, start);
 	unsigned long index;
@@ -2453,16 +2453,25 @@ bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 		goto out;
 	}
 
-	has_attrs = true;
+	has_attrs = match_all;
 	for (index = start; index < end; index++) {
 		do {
 			entry = xas_next(&xas);
 		} while (xas_retry(&xas, entry));
 
-		if (xas.xa_index != index ||
-		    (xa_to_value(entry) & attrs) != attrs) {
-			has_attrs = false;
-			break;
+		if (match_all) {
+			if (xas.xa_index != index ||
+			    (xa_to_value(entry) & attrs) != attrs) {
+				has_attrs = false;
+				break;
+			}
+		} else {
+			index = xas.xa_index;
+			if (index < end &&
+			    (xa_to_value(entry) & attrs) == attrs) {
+				has_attrs = true;
+				break;
+			}
 		}
 	}
 
@@ -2578,7 +2587,7 @@ int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 	lockdep_assert_held(&kvm->slots_arch_lock);
 
 	/* Nothing to do if the entire range as the desired attributes. */
-	if (kvm_range_has_memory_attributes(kvm, start, end, attributes))
+	if (kvm_range_has_memory_attributes(kvm, start, end, attributes, true))
 		return r;
 
 	/*
-- 
2.42.1