[PATCH bpf-next 11/13] selftests/bpf: prevent out-of-bounds stack access in test_bpffs

[Andrii Nakryiko <andrii@xxxxxxxxxx>]

Buf can be not zero-terminated leading to strstr() to access data beyond
the intended buf[] array. Fix by forcing zero termination.

Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/test_bpffs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_bpffs.c b/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
index d29ebfeef9c5..e36782c8ec49 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
@@ -19,11 +19,13 @@ static int read_iter(char *file)
 	fd = open(file, 0);
 	if (fd < 0)
 		return -1;
-	while ((len = read(fd, buf, sizeof(buf))) > 0)
+	while ((len = read(fd, buf, sizeof(buf))) > 0) {
+		buf[sizeof(buf) - 1] = '\0';
 		if (strstr(buf, "iter")) {
 			close(fd);
 			return 0;
 		}
+	}
 	close(fd);
 	return -1;
 }
-- 
2.30.2