[PATCH v3 14/23] arm64: mte: Validate the PROT_MTE request via arch_validate_flags()

Catalin Marinas
2020-04-21T14:26:37Z

Make use of the newly introduced arch_validate_flags() hook to
sanity-check the PROT_MTE request passed to mmap() and mprotect(). If
the mapping does not support MTE, these syscalls will return -EINVAL.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/mman.h | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index c77a23869223..5c356d1ca266 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -44,7 +44,11 @@ static inline unsigned long arch_calc_vm_flag_bits(unsigned long flags)

static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
{
- return (vm_flags & VM_MTE) && (vm_flags & VM_MTE_ALLOWED) ?
+ /*
+ * Checking for VM_MTE only is sufficient since arch_validate_flags()
+ * does not permit (VM_MTE & !VM_MTE_ALLOWED).
+ */
+ return (vm_flags & VM_MTE) ?
__pgprot(PTE_ATTRINDX(MT_NORMAL_TAGGED)) :
__pgprot(0);
}
@@ -61,4 +65,14 @@ static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
}
#define arch_validate_prot arch_validate_prot

+static inline bool arch_validate_flags(unsigned long flags)
+{
+ if (!system_supports_mte())
+ return true;
+
+ /* only allow VM_MTE if VM_MTE_ALLOWED has been set previously */
+ return !(flags & VM_MTE) || (flags & VM_MTE_ALLOWED);
+}
+#define arch_validate_flags arch_validate_flags
+
#endif /* !__ASM_MMAN_H__ */