ubifs: Fix regression in ubifs_readdir()

Commit c83ed4c9dbb35 ("ubifs: Abort readdir upon error") broke
overlayfs support because the fix exposed an internal error
code to VFS.

Reported-by: Peter Rosin <[e-mail]>
Tested-by: Peter Rosin <[e-mail]>
Reported-by: Ralph Sennhauser <[e-mail]>
Tested-by: Ralph Sennhauser <[e-mail]>
Fixes: c83ed4c9dbb35 ("ubifs: Abort readdir upon error")
Cc: [e-mail]
Signed-off-by: Richard Weinberger <[e-mail]>

fs/ubifs/dir.c

···
 
 	if (err != -ENOENT)
 		ubifs_err(c, "cannot find next direntry, error %d", err);
+	else
+		/*
+		 * -ENOENT is a non-fatal error in this context, the TNC uses
+		 * it to indicate that the cursor moved past the current directory
+		 * and readdir() has to stop.
+		 */
+		err = 0;
+
 
 	/* 2 is a special value indicating that there are no more direntries */
 	ctx->pos = 2;