diff mbox series

[v4,2/2] selftest: use mmap instead of posix_memalign to allocate memory

Message ID 20210707184313.3697385-3-pcc@google.com (mailing list archive)
State New
Headers show
Series userfaultfd: do not untag user pointers | expand

Commit Message

Peter Collingbourne July 7, 2021, 6:43 p.m. UTC 
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.

Co-developed-by: Lokesh Gidra <lokeshgidra@google.com>
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Signed-off-by: Peter Collingbourne <pcc@google.com>
Fixes: c47174fc362a ("userfaultfd: selftest")
Cc: <stable@vger.kernel.org> # 5.4
Link: https://linux-review.googlesource.com/id/Icac91064fcd923f77a83e8e133f8631c5b8fc241
---
 tools/testing/selftests/vm/userfaultfd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Catalin Marinas July 8, 2021, 12:59 p.m. UTC | #1 
On Wed, Jul 07, 2021 at 11:43:13AM -0700, Peter Collingbourne wrote:
> 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.
> 
> Co-developed-by: Lokesh Gidra <lokeshgidra@google.com>
> Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Fixes: c47174fc362a ("userfaultfd: selftest")
> Cc: <stable@vger.kernel.org> # 5.4
> Link: https://linux-review.googlesource.com/id/Icac91064fcd923f77a83e8e133f8631c5b8fc241

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Andrew Morton July 9, 2021, 11:27 p.m. UTC | #2 
On Wed,  7 Jul 2021 11:43:13 -0700 Peter Collingbourne <pcc@google.com> wrote:

> 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.

Doesn't apply to current mainline.  Can you please resync and redo?

> Co-developed-by: Lokesh Gidra <lokeshgidra@google.com>
> Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Fixes: c47174fc362a ("userfaultfd: selftest")
> Cc: <stable@vger.kernel.org> # 5.4

This patch then won't apply to earlier kenrels, so please be prepared
to help Greg resolve this.
diff mbox series

Patch

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index f5ab5e0312e7..d0f802053dfd 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -197,8 +197,10 @@  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, "anon memory mmap failed\n");
 		*alloc_area = NULL;
 	}
 }