[PATCH v2 2/2] selftests/filesystems: allow security.selinux xattr in listxattr kernfs test

[Disha Goel <disgoel@linux.ibm.com>]

kernfs_test assumes that flistxattr() on /sys/kernel/warn_count always
returns an empty list. However, systems with SELinux enabled may expose
security.selinux xattr via listxattr() during policy load, which makes
the test fail even though kernfs is behaving correctly.

Allow security.selinux xattr in kernfs_listxattr while continuing to
reject other unexpected xattrs. Keep the existing user.foo getxattr
check unchanged.

This avoids false failures on SELinux-enabled systems while preserving
the original purpose of the test.

Signed-off-by: Disha Goel <disgoel@linux.ibm.com>
---
 .../selftests/filesystems/kernfs_test.c       | 27 +++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/filesystems/kernfs_test.c b/tools/testing/selftests/filesystems/kernfs_test.c
index 84c2b910a60d..a5e480d662e0 100644
--- a/tools/testing/selftests/filesystems/kernfs_test.c
+++ b/tools/testing/selftests/filesystems/kernfs_test.c
@@ -4,6 +4,8 @@
 
 #include <fcntl.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <sys/xattr.h>
 
@@ -12,12 +14,33 @@
 
 TEST(kernfs_listxattr)
 {
+	char *buf, *xattr;
+	ssize_t len, ret;
 	int fd;
 
-	/* Read-only file that can never have any extended attributes set. */
+	/* Read-only file that can never have any extended attributes set.
+	 * However, SELinux may set security.selinux xattr on kernfs files
+	 * during policy load, so we explicitly ignore it.
+	 */
 	fd = open("/sys/kernel/warn_count", O_RDONLY | O_CLOEXEC);
 	ASSERT_GE(fd, 0);
-	ASSERT_EQ(flistxattr(fd, NULL, 0), 0);
+
+	len = flistxattr(fd, NULL, 0);
+	ASSERT_GE(len, 0);
+
+	if (len > 0) {
+		buf = malloc(len);
+		ASSERT_NE(buf, NULL);
+
+		ret = flistxattr(fd, buf, len);
+		ASSERT_EQ(ret, len);
+
+		for (xattr = buf; xattr < buf + len; xattr += strlen(xattr) + 1)
+			ASSERT_EQ(strcmp(xattr, "security.selinux"), 0);
+
+		free(buf);
+	}
+
 	EXPECT_EQ(close(fd), 0);
 }
 
-- 
2.45.1