client: Gracefully handle empty pathname for chownat()

man fchownat(2)[1] says the following:
. . .
AT_EMPTY_PATH (since Linux 2.6.39)
    If pathname is an empty string, operate on the file referred to by
    dirfd (which may have been obtained using the open(2) O_PATH flag).
    In this case, dirfd can refer to any type of file, not just a
    directory. If dirfd is AT_FDCWD, the call operates on the current
    working directory.
. . .

Look out for an empty pathname and use the relative fd's inode in the
presence of AT_EMPTY_PATH flag before calling internal _setattr().

Fixes: https://tracker.ceph.com/issues/68189
Review with: git show -w

Note: path_walk() refactor from https://github.com/ceph/ceph/pull/60746
included the core changes required here and thus src/client/Client.cc
changes have been removed from the cherry-pick as they conflict at the
same time.

[1] https://www.man7.org/linux/man-pages/man2/fchownat.2.html

Signed-off-by: Anoop C S <anoopcs@cryptolab.net>
(cherry picked from commit 829f38899226fcd1f603ba446b018f53c5b0921d)

diff --git a/src/include/cephfs/libcephfs.h b/src/include/cephfs/libcephfs.h
index d0fa9e6b28c565de5a9bf68919e31cdc196a7fff..7d3024195ac893cd463ac2252831a5379420e172 100644 (file)
--- a/src/include/cephfs/libcephfs.h
+++ b/src/include/cephfs/libcephfs.h
@@ -1115,7 +1115,7 @@ int ceph_lchown(struct ceph_mount_info *cmount, const char *path, int uid, int g
  * @param relpath the relpath of the file/directory to change the ownership of.
  * @param uid the user id to set on the file/directory.
  * @param gid the group id to set on the file/directory.
- * @param flags bitfield that can be used to set AT_* modifier flags (AT_SYMLINK_NOFOLLOW)
+ * @param flags bitfield that can be used to set AT_* modifier flags (AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH)
  * @returns 0 on success or negative error code on failure.
  */
 int ceph_chownat(struct ceph_mount_info *cmount, int dirfd, const char *relpath,

diff --git a/src/test/libcephfs/test.cc b/src/test/libcephfs/test.cc
index 9d1e84a4f85d88d5e68f8622e75e9c24a049c758..bcdba534cb3b9b29b9dfda2d8e59b86bdc22a77d 100644 (file)
--- a/src/test/libcephfs/test.cc
+++ b/src/test/libcephfs/test.cc
@@ -3438,6 +3438,13 @@ TEST(LibCephFS, Chownat) {
   // change ownership to nobody -- we assume nobody exists and id is always 65534
   ASSERT_EQ(ceph_conf_set(cmount, "client_permissions", "0"), 0);
   ASSERT_EQ(ceph_chownat(cmount, fd, rel_file_path, 65534, 65534, 0), 0);
+  // change relative fd ownership with AT_EMPTY_PATH
+#if defined(__linux__) && defined(AT_EMPTY_PATH)
+  int file_fd = ceph_openat(cmount, fd, rel_file_path, O_RDONLY, 0);
+  ASSERT_LE(0, file_fd);
+  ASSERT_EQ(ceph_chownat(cmount, file_fd, "", 65534, 65534, AT_EMPTY_PATH), 0);
+  ceph_close(cmount, file_fd);
+#endif
   ASSERT_EQ(ceph_conf_set(cmount, "client_permissions", "1"), 0);
   ceph_close(cmount, fd);