Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fix from Catalin Marinas:
 "Fix PTRACE_PEEKMTETAGS access to an mmapped region before the first
  write"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: mte: Allow PTRACE_PEEKMTETAGS access to the zero page

2 files changed, 3 insertions, 6 deletions

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e99eddec0a46..3e6331b64932 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1701,16 +1701,12 @@ static void bti_enable(const struct arm64_cpu_capabilities *__unused)
 #ifdef CONFIG_ARM64_MTE
 static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap)
 {
-	static bool cleared_zero_page = false;
-
 	/*
 	 * Clear the tags in the zero page. This needs to be done via the
 	 * linear map which has the Tagged attribute.
 	 */
-	if (!cleared_zero_page) {
-		cleared_zero_page = true;
+	if (!test_and_set_bit(PG_mte_tagged, &ZERO_PAGE(0)->flags))
 		mte_clear_page_tags(lm_alias(empty_zero_page));
-	}
 
 	kasan_init_hw_tags_cpu();
 }
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index dc9ada64feed..80b62fe49dcf 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -329,11 +329,12 @@ static int __access_remote_tags(struct mm_struct *mm, unsigned long addr,
 		 * would cause the existing tags to be cleared if the page
 		 * was never mapped with PROT_MTE.
 		 */
-		if (!test_bit(PG_mte_tagged, &page->flags)) {
+		if (!(vma->vm_flags & VM_MTE)) {
 			ret = -EOPNOTSUPP;
 			put_page(page);
 			break;
 		}
+		WARN_ON_ONCE(!test_bit(PG_mte_tagged, &page->flags));
 
 		/* limit access to the end of the page */
 		offset = offset_in_page(addr);