[PATCH] mm: perform MTE check within arm64 hook entirely

[Lorenzo Stoakes]

It doesn't make sense to have shmem explicitly check this one arch-specific
case, it is arch-specific, so the arch should handle it. We know shmem is a
case in which we want to permit MTE, so simply check for this directly.

This also fixes the issue with checking arch_validate_flags() early, which
would otherwise break mmap_region().

In order to implement this we must pass a file pointer, and additionally
update the sparc code to accept this parameter too.

We'd ideally like to have eliminated the arch_calc_vm_flag_bits() case, but
we risk inadvertently changing behaviour as we do not have mmap() flags
available at the point of the arch_validate_flags() check and a MAP_ANON |
MAP_HUGETLB case would be accepted for MTE currently, but a MAP_SHARED |
MAP_HUGETLB would not.

This is likely an oversight but we want to try to keep behaviour identical
to before in this patch.

So continue to check VM_MTE_ALLOWED which arch_calc_vm_flag_bits() sets if
MAP_ANON.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
 arch/arm64/include/asm/mman.h | 18 ++++++++++++++----
 arch/sparc/include/asm/mman.h |  5 +++--
 include/linux/mman.h          |  2 +-
 mm/mmap.c                     |  4 ++--
 mm/mprotect.c                 |  2 +-
 mm/shmem.c                    |  3 ---
 6 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index 9e39217b4afb..44b7c8a1dd67 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -6,7 +6,9 @@

 #ifndef BUILD_VDSO
 #include <linux/compiler.h>
+#include <linux/fs.h>
 #include <linux/types.h>
+#include <linux/shmem_fs.h>

 static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
 	unsigned long pkey)
@@ -60,15 +62,23 @@ static inline bool arch_validate_prot(unsigned long prot,
 }
 #define arch_validate_prot(prot, addr) arch_validate_prot(prot, addr)

-static inline bool arch_validate_flags(unsigned long vm_flags)
+static inline bool arch_validate_flags(struct file *file, unsigned long vm_flags)
 {
 	if (!system_supports_mte())
 		return true;

-	/* only allow VM_MTE if VM_MTE_ALLOWED has been set previously */
-	return !(vm_flags & VM_MTE) || (vm_flags & VM_MTE_ALLOWED);
+	if (!(vm_flags & VM_MTE))
+		return true;
+
+	if (vm_flags & VM_MTE_ALLOWED)
+		return true;
+
+	if (shmem_file(file))
+		return true;
+
+	return false;
 }
-#define arch_validate_flags(vm_flags) arch_validate_flags(vm_flags)
+#define arch_validate_flags(file, vm_flags) arch_validate_flags(file, vm_flags)

 #endif /* !BUILD_VDSO */

diff --git a/arch/sparc/include/asm/mman.h b/arch/sparc/include/asm/mman.h
index af9c10c83dc5..d426e1f7c2c1 100644
--- a/arch/sparc/include/asm/mman.h
+++ b/arch/sparc/include/asm/mman.h
@@ -10,6 +10,7 @@ int sparc_mmap_check(unsigned long addr, unsigned long len);

 #ifdef CONFIG_SPARC64
 #include <asm/adi_64.h>
+#include <linux/fs.h>

 static inline void ipi_set_tstate_mcde(void *arg)
 {
@@ -54,11 +55,11 @@ static inline int sparc_validate_prot(unsigned long prot, unsigned long addr)
 	return 1;
 }

-#define arch_validate_flags(vm_flags) arch_validate_flags(vm_flags)
+#define arch_validate_flags(file, vm_flags) arch_validate_flags(file, vm_flags)
 /* arch_validate_flags() - Ensure combination of flags is valid for a
  *	VMA.
  */
-static inline bool arch_validate_flags(unsigned long vm_flags)
+static inline bool arch_validate_flags(struct file *file, unsigned long vm_flags)
 {
 	/* If ADI is being enabled on this VMA, check for ADI
 	 * capability on the platform and ensure VMA is suitable
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 8ddca62d6460..82e6488026b7 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -117,7 +117,7 @@ static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
  *
  * Returns true if the VM_* flags are valid.
  */
-static inline bool arch_validate_flags(unsigned long flags)
+static inline bool arch_validate_flags(struct file *file, unsigned long flags)
 {
 	return true;
 }
diff --git a/mm/mmap.c b/mm/mmap.c
index 8462de1ee583..e06171d243ef 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1504,7 +1504,7 @@ static unsigned long __mmap_region(struct file *file, unsigned long addr,

 #ifdef CONFIG_SPARC64
 	/* TODO: Fix SPARC ADI! */
-	WARN_ON_ONCE(!arch_validate_flags(vm_flags));
+	WARN_ON_ONCE(!arch_validate_flags(file, vm_flags));
 #endif

 	/* Lock the VMA since it is modified after insertion into VMA tree */
@@ -1587,7 +1587,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		return -EACCES;

 	/* Allow architectures to sanity-check the vm_flags. */
-	if (!arch_validate_flags(vm_flags))
+	if (!arch_validate_flags(file, vm_flags))
 		return -EINVAL;

 	/* Map writable and ensure this isn't a sealed memfd. */
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 6f450af3252e..c6db98b893fc 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -816,7 +816,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		}

 		/* Allow architectures to sanity-check the new flags */
-		if (!arch_validate_flags(newflags)) {
+		if (!arch_validate_flags(vma->vm_file, newflags)) {
 			error = -EINVAL;
 			break;
 		}
diff --git a/mm/shmem.c b/mm/shmem.c
index 4ba1d00fabda..e87f5d6799a7 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2733,9 +2733,6 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 	if (ret)
 		return ret;

-	/* arm64 - allow memory tagging on RAM-based files */
-	vm_flags_set(vma, VM_MTE_ALLOWED);
-
 	file_accessed(file);
 	/* This is anonymous shared memory if it is unlinked at the time of mmap */
 	if (inode->i_nlink)
--
2.47.0