udf: Detect incorrect directory size

Detect when a directory entry is (possibly partially) beyond directory
size and return EIO in that case since it means the filesystem is
corrupted. Otherwise directory operations can further corrupt the
directory and possibly also oops the kernel.

CC: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
CC: stable@vger.kernel.org
Reported-and-tested-by: NAnatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: NJan Kara <jack@suse.cz>

fs/udf/directory.c

@@ -152,6 +152,9 @@ struct fileIdentDesc *udf_fileident_read(struct inode *dir, loff_t *nf_pos,
 			       sizeof(struct fileIdentDesc));
 		}
 	}
+	/* Got last entry outside of dir size - fs is corrupted! */
+	if (*nf_pos > dir->i_size)
+		return NULL;
 	return fi;
 }