selftests/bpf: Accept unnamed dma-bufs in the dmabuf_iter default test

The dmabuf_collector iterator prints the inode, size, name and exporter
of every dma-buf in the system on separate lines, with an empty name for
the buffers that have none. The default_iter subtest parses that output
and looks for the two buffers it created.

It requires a name for every buffer, and sscanf() finds none on the
empty line of an unnamed one. On a system that has such a buffer, like
one exported by udmabuf without a name, the subtest fails before it
gets to its own buffers.

Take an empty name for a buffer without one.

Fixes: ae5d2c59ecd7 ("selftests/bpf: Add test for dmabuf_iter")
Signed-off-by: Qiliang Yuan <odys.yuan@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Link: https://lore.kernel.org/bpf/20261009-selftests-bpf-dmabuf-iter-unnamed-v1-1-962ee94f7a5e@gmail.com

1 files changed, 3 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
index fb2cea710db3..1a5dc1adae73 100644
--- a/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
@@ -188,8 +188,9 @@ static void subtest_dmabuf_iter_check_default_iter(struct dmabuf_iter *skel)
 			ASSERT_EQ(sscanf(line, "%ld", &bufinfo.size), 1,
 				  "read size");
 		} else if (f % FIELD_COUNT == NAME) {
-			ASSERT_EQ(sscanf(line, "%s", bufinfo.name), 1,
-				  "read name");
+			/* Keep an empty name for a buffer without one */
+			if (sscanf(line, "%s", bufinfo.name) != 1)
+				bufinfo.name[0] = '\0';
 		} else if (f % FIELD_COUNT == EXPORTER) {
 			ASSERT_EQ(sscanf(line, "%31s", bufinfo.exporter), 1,
 				  "read exporter");