mm: reject vmap with VM_FLUSH_RESET_PERMS

Patch series "cleanup vfree and vunmap".

This little series untangles the vfree and vunmap code path a bit.


This patch (of 10):

VM_FLUSH_RESET_PERMS is just for use with vmalloc as it is tied to freeing
the underlying pages.

Link: https://lkml.kernel.org/r/20230121071051.1143058-1-hch@lst.de
Link: https://lkml.kernel.org/r/20230121071051.1143058-2-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmalloc.c

@@ -2868,6 +2868,9 @@ void *vmap(struct page **pages, unsigned int count,
 
 	might_sleep();
 
+	if (WARN_ON_ONCE(flags & VM_FLUSH_RESET_PERMS))
+		return NULL;
+
 	/*
 	 * Your top guard is someone else's bottom guard. Not having a top
 	 * guard compromises someone else's mappings too.