Re: [PATCH v5 15/25] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files

Since arm64 memory (allocation) tags can only be stored in RAM, mapping
files with PROT_MTE is not allowed by default. RAM-based files like
those in a tmpfs mount or memfd_create() can support memory tagging, so
update the vm_flags accordingly in shmem_mmap().

...

--- a/mm/shmem.c
+++ b/mm/shmem.c

@@ -2206,6 +2206,9 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 			vma->vm_flags &= ~(VM_MAYWRITE);
 	}
 
+	/* arm64 - allow memory tagging on RAM-based files */
+	vma->vm_flags |= VM_MTE_ALLOWED;
+
 	file_accessed(file);
 	vma->vm_ops = &shmem_vm_ops;
 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&