linux-kernel - [PATCH 3/4] arm64: mte: update code comments

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241028094014.2596619-4-aneesh.kumar@kernel.org>
Date: Mon, 28 Oct 2024 15:10:13 +0530
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Cc: Suzuki K Poulose <Suzuki.Poulose@....com>,
	Steven Price <steven.price@....com>,
	Will Deacon <will@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
Subject: [PATCH 3/4] arm64: mte: update code comments

commit d77e59a8fccd ("arm64: mte: Lock a page for MTE tag
initialisation") updated the locking such the kernel now allows
VM_SHARED mapping with MTE. Update the code comment to reflect this.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
---
 arch/arm64/kvm/mmu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index a509b63bd4dd..b5824e93cee0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1390,11 +1390,8 @@ static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
  * able to see the page's tags and therefore they must be initialised first. If
  * PG_mte_tagged is set, tags have already been initialised.
  *
- * The race in the test/set of the PG_mte_tagged flag is handled by:
- * - preventing VM_SHARED mappings in a memslot with MTE preventing two VMs
- *   racing to santise the same page
- * - mmap_lock protects between a VM faulting a page in and the VMM performing
- *   an mprotect() to add VM_MTE
+ * The race in the test/set of the PG_mte_tagged flag is handled by
+ * using PG_mte_lock and PG_mte_tagged together.
  */
 static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
 			      unsigned long size)
@@ -1646,7 +1643,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	}
 
 	if (!fault_is_perm && !device && kvm_has_mte(kvm)) {
-		/* Check the VMM hasn't introduced a new disallowed VMA */
+		/*
+		 *  not a permission fault implies a translation fault which
+		 *  means mapping the page for the first time
+		 */
 		if (mte_allowed) {
 			sanitise_mte_tags(kvm, pfn, vma_pagesize);
 		} else {
-- 
2.43.0