Commit 9351590f authored Sep 09, 2021 by Enzo Matsumiya Committed by Steve French Sep 09, 2021

cifs: properly invalidate cached root handle when closing it



Cached root file was not being completely invalidated sometimes.

Reproducing:
- With a DFS share with 2 targets, one disabled and one enabled
- start some I/O on the mount
  # while true; do ls /mnt/dfs; done
- at the same time, disable the enabled target and enable the disabled
  one
- wait for DFS cache to expire
- on reconnect, the previous cached root handle should be invalid, but
  open_cached_dir_by_dentry() will still try to use it, but throws a
  use-after-free warning (kref_get())

Make smb2_close_cached_fid() invalidate all fields every time, but only
send an SMB2_close() when the entry is still valid.

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

parent 8d014f5f

fs/cifs/smb2ops.c

+13 −7

Original line number	Diff line number	Diff line
		@@ -689,6 +689,13 @@ smb2_close_cached_fid(struct kref *ref)
		cifs_dbg(FYI, "clear cached root file handle\n");
		SMB2_close(0, cfid->tcon, cfid->fid->persistent_fid,
		cfid->fid->volatile_fid);
		}

		/*
		* We only check validity above to send SMB2_close,
		* but we still need to invalidate these entries
		* when this function is called
		*/
		cfid->is_valid = false;
		cfid->file_all_info_is_valid = false;
		cfid->has_lease = false;
		@@ -697,7 +704,6 @@ smb2_close_cached_fid(struct kref *ref)
		cfid->dentry = NULL;
		}
		}
		}

		void close_cached_dir(struct cached_fid *cfid)
		{