selftest: use mmap instead of posix_memalign to allocate memory

commit 0db282ba2c12c1515d490d14a1ff696643ab0f1b upstream.

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.

Link: https://lkml.kernel.org/r/20210714195437.118982-3-pcc@google.com
Link: https://linux-review.googlesource.com/id/Icac91064fcd923f77a83e8e133f8631c5b8fc241
Fixes: c47174fc362a ("userfaultfd: selftest")
Co-developed-by: Lokesh Gidra <lokeshgidra@google.com>
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Alistair Delva <adelva@google.com>
Cc: William McVicker <willmcvicker@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mitch Phillips <mitchp@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: <stable@vger.kernel.org>	[5.4]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 7b8171e3128a8715a62a10e020c69ea3ca1c5321..16d42b2de424e575b0db29b0b5924a1ba65c12ff 100644 (file)
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -129,8 +129,10 @@ static int 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)) {
-               fprintf(stderr, "out of memory\n");
+       *alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
+                          MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+       if (*alloc_area == MAP_FAILED)
+               fprintf(stderr, "mmap of anonymous memory failed");
                *alloc_area = NULL;
        }
 }