FAILED: patch "[PATCH] selftest: use mmap instead of posix_memalign to allocate" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0db282ba2c12c1515d490d14a1ff696643ab0f1b Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <[email protected]>
Date: Fri, 23 Jul 2021 15:50:04 -0700
Subject: [PATCH] selftest: use mmap instead of posix_memalign to allocate
memory

This test passes pointers obtained from anon_allocate_area to the userfaultfd and mremap APIs. This causes a problem if the system allocator returns tagged pointers because with the tagged address ABI the kernel rejects tagged addresses passed to these APIs, which would end up causing the test to fail. To make this test compatible with such system allocators, stop using the system allocator to allocate memory in anon_allocate_area, and instead just use mmap.

index e363bdaff59d..2ea438e6b8b1 100644
@@ -210,8 +210,10 @@ static void anon_release_pages(char *rel_area)
 
 static void anon_allocate_area(void **alloc_area)
 {
-	if (posix_memalign(alloc_area, page_size, nr_pages * page_size))
-		err("posix_memalign() failed");
+	*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
+			   MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (*alloc_area == MAP_FAILED)
+		err("mmap of anonymous memory failed");
 }
 
 static void noop_alias_mapping(__u64 *start, size_t len, unsigned long offset)