arm64: mte: Do not allow PROT_MTE on MAP_HUGETLB user mappings

PROT_MTE (memory tagging extensions) is not supported on all user mmap()
types for various reasons (memory attributes, backing storage, CoW
handling). The arm64 arch_validate_flags() function checks whether the
VM_MTE_ALLOWED flag has been set for a vma during mmap(), usually by
arch_calc_vm_flag_bits().

Linux prior to 6.13 does not support PROT_MTE hugetlb mappings. This was
added by commit 25c17c4b55de ("hugetlb: arm64: add mte support").
However, earlier kernels inadvertently set VM_MTE_ALLOWED on
(MAP_ANONYMOUS | MAP_HUGETLB) mappings by only checking for
MAP_ANONYMOUS.

Explicitly check MAP_HUGETLB in arch_calc_vm_flag_bits() and avoid
setting VM_MTE_ALLOWED for such mappings.

Fixes: 9f3419315f3c ("arm64: mte: Add PROT_MTE support to mmap() and mprotect()")
Cc: <stable@vger.kernel.org> # 5.10.x-6.12.x
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index 56bc2e4e81a6e9f6245c41409e36f13b8d86f8b7..0070ee4ba8955f14907a7e16ceb27d0ba16b1744 100644 (file)
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -31,9 +31,12 @@ static inline unsigned long arch_calc_vm_flag_bits(struct file *file,
         * backed by tags-capable memory. The vm_flags may be overridden by a
         * filesystem supporting MTE (RAM-based).
         */
-       if (system_supports_mte() &&
-           ((flags & MAP_ANONYMOUS) || shmem_file(file)))
-               return VM_MTE_ALLOWED;
+       if (system_supports_mte()) {
+               if ((flags & MAP_ANONYMOUS) && !(flags & MAP_HUGETLB))
+                       return VM_MTE_ALLOWED;
+               if (shmem_file(file))
+                       return VM_MTE_ALLOWED;
+       }
 
        return 0;
 }