io: Add tst-lstat-nofollow, tst-lstat-nofollow-time64

They verify that lstat, lstat64 do not follow symbolic links.

Reviewed-by: DJ Delorie <dj@redhat.com>

io/Makefile

@@ -208,6 +208,7 @@ tests := \
   tst-lchmod \
   tst-linkat \
   tst-lockf \
+  tst-lstat-nofollow \
   tst-lutimes \
   tst-mkdirat \
   tst-mkfifoat \
@@ -237,6 +238,7 @@ tests-time64 := \
   tst-futimes-time64\
   tst-futimesat-time64 \
   tst-lchmod-time64 \
+  tst-lstat-nofollow-time64 \
   tst-lutimes-time64 \
   tst-stat-time64 \
   tst-utime-time64 \

io/tst-lstat-nofollow-time64.c

@@ -0,0 +1 @@
+#include "tst-lstat-nofollow.c"

io/tst-lstat-nofollow.c

@@ -0,0 +1,98 @@
+/* Test that lstat does not follow symbolic links.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <support/check.h>
+#include <support/fuse.h>
+#include <support/support.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+static void
+fuse_thread (struct support_fuse *f, void *closure)
+{
+  struct fuse_in_header *inh;
+  while ((inh = support_fuse_next (f)) != NULL)
+    {
+      if (support_fuse_handle_mountpoint (f)
+          || (inh->nodeid == 1 && support_fuse_handle_directory (f)))
+        continue;
+      switch (inh->opcode)
+        {
+        case FUSE_LOOKUP:
+          {
+            TEST_COMPARE (inh->nodeid, 1);
+            TEST_COMPARE_STRING (support_fuse_cast (LOOKUP, inh), "symlink");
+            struct fuse_entry_out *out = support_fuse_prepare_entry (f, 2);
+            out->attr.mode = S_IFLNK | 0777;
+            out->attr.size = strlen ("target");
+            support_fuse_reply_prepared (f);
+          }
+          break;
+        case FUSE_GETATTR:
+          {
+            TEST_COMPARE (inh->nodeid, 2);
+            struct fuse_attr_out *out = support_fuse_prepare_attr (f);
+            out->attr.mode = S_IFLNK | 0777;
+            out->attr.size = strlen ("target");
+            support_fuse_reply_prepared (f);
+          }
+          break;
+        case FUSE_READLINK:
+          /* The lstat operation must not attempt to look at the
+             symbolic link target.  */
+          FAIL ("attempt to obtain target of symblic link for node %llu",
+                (unsigned long long int) inh->nodeid);
+          break;
+        default:
+          FAIL ("unexpected event %s", support_fuse_opcode (inh->opcode));
+        }
+    }
+}
+
+static int
+do_test (void)
+{
+  support_fuse_init ();
+  struct support_fuse *f = support_fuse_mount (fuse_thread, NULL);
+  char *symlink_path = xasprintf ("%s/symlink", support_fuse_mountpoint (f));
+
+  {
+    struct stat st = { 0, };
+    TEST_COMPARE (lstat (symlink_path, &st), 0);
+    TEST_COMPARE (st.st_uid, getuid ());
+    TEST_COMPARE (st.st_gid, getgid ());
+    TEST_COMPARE (st.st_size, 6);
+    TEST_COMPARE (st.st_mode, S_IFLNK | 0777);
+  }
+
+  {
+    struct stat64 st = { 0, };
+    TEST_COMPARE (lstat64 (symlink_path, &st), 0);
+    TEST_COMPARE (st.st_uid, getuid ());
+    TEST_COMPARE (st.st_gid, getgid ());
+    TEST_COMPARE (st.st_size, 6);
+    TEST_COMPARE (st.st_mode, S_IFLNK | 0777);
+  }
+
+  free (symlink_path);
+  support_fuse_unmount (f);
+  return 0;
+}
+
+#include <support/test-driver.c>