Merge PR ceph#59503 into main

* refs/pull/59503/head:
	client: Resolve symlink from dirfd for empty pathname
	client: Fix symlink open with O_PATH and O_NOFOLLOW

Reviewed-by: Venky Shankar <[email protected]>
Reviewed-by: Dhairya Parmar <[email protected]>

Author: vshankar

src/client/Client.cc

@@ -6125,6 +6125,10 @@ int Client::may_open(Inode *in, int flags, const UserPerm& perms)
   int r = 0;
   switch (in->mode & S_IFMT) {
     case S_IFLNK:
+#if defined(__linux__) && defined(O_PATH)
+      if (flags & O_PATH)
+        break;
+#endif
       r = -CEPHFS_ELOOP;
       goto out;
     case S_IFDIR:
@@ -7953,6 +7957,12 @@ int Client::readlinkat(int dirfd, const char *relpath, char *buf, loff_t size, c
     return r;
   }
 
+  if (!strcmp(relpath, "")) {
+    if (!dirinode.get()->is_symlink())
+      return -CEPHFS_ENOENT;
+    return _readlink(dirinode.get(), buf, size);
+  }
+
   InodeRef in;
   filepath path(relpath);
   r = path_walk(path, &in, perms, false, 0, dirinode);

src/test/libcephfs/test.cc

@@ -976,6 +976,13 @@ TEST(LibCephFS, Symlinks) {
   fd = ceph_open(cmount, test_symlink, O_NOFOLLOW, 0);
   ASSERT_EQ(fd, -CEPHFS_ELOOP);
 
+#if defined(__linux__) && defined(O_PATH)
+  // test the O_NOFOLLOW with O_PATH case
+  fd = ceph_open(cmount, test_symlink, O_PATH|O_NOFOLLOW, 0);
+  ASSERT_GT(fd, 0);
+  ceph_close(cmount, fd);
+#endif /* __linux */
+
   // stat the original file
   struct ceph_statx stx_orig;
   ASSERT_EQ(ceph_statx(cmount, test_file, &stx_orig, CEPH_STATX_ALL_STATS, 0), 0);
@@ -3012,6 +3019,18 @@ TEST(LibCephFS, Readlinkat) {
   ASSERT_EQ(0, memcmp(target, rel_file_path, target_len));
 
   ASSERT_EQ(0, ceph_close(cmount, fd));
+#if defined(__linux__) && defined(O_PATH)
+  // test readlinkat with empty pathname relative to O_PATH|O_NOFOLLOW fd
+  fd = ceph_open(cmount, link_path, O_PATH | O_NOFOLLOW, 0);
+  ASSERT_LE(0, fd);
+  size_t link_target_len = strlen(rel_file_path);
+  char link_target[link_target_len+1];
+  ASSERT_EQ(link_target_len, ceph_readlinkat(cmount, fd, "", link_target, link_target_len));
+  link_target[link_target_len] = '\0';
+  ASSERT_EQ(0, memcmp(link_target, rel_file_path, link_target_len));
+  ASSERT_EQ(0, ceph_close(cmount, fd));
+#endif /* __linux */
+
   ASSERT_EQ(0, ceph_unlink(cmount, link_path));
   ASSERT_EQ(0, ceph_unlink(cmount, file_path));
   ASSERT_EQ(0, ceph_rmdir(cmount, dir_path));