tests: support both old and new landlock pseudopath

Since the ABI of landlock ruleset file name has been broken by Linux
commit v5.18-rc1~88^2, the landlock_create_ruleset-y now has to account
for both new and old possible names.  Opt for checking the link value
in the test instead.

* tests/landlock_create_ruleset-y.c (FD_PATH): Remove.
(DECODE_FD): New macro.
* tests/landlock_create_ruleset.c: Include "xmalloc.h" and <stdlib.h>.
[!DECODE_FD] (DECODE_FD): New macro.
(main) <fd_str>: New variable.
[DECODE_FD] (main): Check the link path of the fd returned
by the landlock_create_ruleset call and set it to fd_str, which
is then printed.

2 files changed, 33 insertions, 2 deletions

diff --git a/tests/landlock_create_ruleset-y.c b/tests/landlock_create_ruleset-y.c
index 50e19c2d5..87632fd34 100644
--- a/tests/landlock_create_ruleset-y.c
+++ b/tests/landlock_create_ruleset-y.c
@@ -1,4 +1,4 @@
-#define FD_PATH "<anon_inode:[landlock-ruleset]>"
+#define DECODE_FD 1
 #define SKIP_IF_PROC_IS_UNAVAILABLE skip_if_unavailable("/proc/self/fd/")
 
 #include "landlock_create_ruleset.c"
diff --git a/tests/landlock_create_ruleset.c b/tests/landlock_create_ruleset.c
index bc1bcc2cf..476c40236 100644
--- a/tests/landlock_create_ruleset.c
+++ b/tests/landlock_create_ruleset.c
@@ -9,10 +9,12 @@
 
 #include "tests.h"
 #include "scno.h"
+#include "xmalloc.h"
 
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #include <linux/landlock.h>
@@ -20,6 +22,9 @@
 #ifndef RETVAL_INJECTED
 # define RETVAL_INJECTED 0
 #endif
+#ifndef DECODE_FD
+# define DECODE_FD 0
+#endif
 
 #ifndef SKIP_IF_PROC_IS_UNAVAILABLE
 # define SKIP_IF_PROC_IS_UNAVAILABLE
@@ -124,14 +129,40 @@ main(void)
 	static const kernel_ulong_t sizes[] = { 8, 12, 16 };
 	for (size_t i = 0; i < ARRAY_SIZE(attr_vals); i++) {
 		for (size_t j = 0; j < ARRAY_SIZE(sizes); j++) {
+			const char *fd_str = FD_PATH;
+
 			attr->handled_access_fs = attr_vals[i].val;
 			rc = sys_landlock_create_ruleset(attr, sizes[j], 0);
+
+#if DECODE_FD
+			/*
+			 * The ABI has been broken in commit v5.18-rc1~88^2
+			 * by adding brackets to the link value, hence, we can't
+			 * rely on a specific name anymore and have to fetch it
+			 * ourselves.
+			 */
+			if (rc >= 0) {
+				static char buf[256];
+				char *path = xasprintf("/proc/self/fd/%ld", rc);
+				ssize_t ret = readlink(path, buf + 1,
+						       sizeof(buf) - 3);
+				free(path);
+
+				if (ret >= 0) {
+					buf[0] = '<';
+					buf[ret + 1] = '>';
+					buf[ret + 2] = '\0';
+					fd_str = buf;
+				}
+			}
+#endif
+
 			printf("landlock_create_ruleset({handled_access_fs=%s"
 			       "%s}, %llu, 0) = %s%s" INJ_STR,
 			       attr_vals[i].str,
 			       sizes[j] > sizeof(*attr) ? ", ..." : "",
 			       (unsigned long long) sizes[j],
-			       errstr, rc > 0 ? FD_PATH : "");
+			       errstr, rc >= 0 ? fd_str : "");
 		}
 	}