mm: Introduce arch_validate_flags()

Similarly to arch_validate_prot() called from do_mprotect_pkey(), an
architecture may need to sanity-check the new vm_flags.

Define a dummy function always returning true. In addition to
do_mprotect_pkey(), also invoke it from mmap_region() prior to updating
vma->vm_page_prot to allow the architecture code to veto potentially
inconsistent vm_flags.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/mm/mprotect.c b/mm/mprotect.c
index ce8b8a5eacbb..56c02beb6041 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -603,6 +603,12 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 			goto out;
 		}
 
+		/* Allow architectures to sanity-check the new flags */
+		if (!arch_validate_flags(newflags)) {
+			error = -EINVAL;
+			goto out;
+		}
+
 		error = security_file_mprotect(vma, reqprot, prot);
 		if (error)
 			goto out;