From: Ernesto =?utf-8?Q?A=2E_Fern=C3=A1ndez?= Subject: [PATCH] ext2: Fix memory leak when truncate races ext2_get_blocks Date: Fri, 23 Jun 2017 21:37:21 -0300 Message-ID: <20170624003719.GA5670@debian.home> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit To: jack@suse.com, linux-ext4@vger.kernel.org Return-path: Received: from mail-qk0-f195.google.com ([209.85.220.195]:34090 "EHLO mail-qk0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754075AbdFXAh0 (ORCPT ); Fri, 23 Jun 2017 20:37:26 -0400 Received: by mail-qk0-f195.google.com with SMTP id 91so2377768qkq.1 for ; Fri, 23 Jun 2017 17:37:25 -0700 (PDT) Content-Disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: Buffer heads referencing indirect blocks may not be released if the file is truncated at the right time. This happens because ext2_get_branch() returns NULL when it finds the whole chain of indirect blocks already set, and when truncate alters the chain this value of NULL is treated as the address of the last head to be released. Handle this in the same way as it's done after the got_it label. Signed-off-by: Ernesto A. Fernández --- Despite trying I haven't actually managed to trigger this race. I tested the patch by inducing regular failures in verify_chain(). fs/ext2/inode.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c index 2dcbd56..30163d0 100644 --- a/fs/ext2/inode.c +++ b/fs/ext2/inode.c @@ -659,6 +659,7 @@ static int ext2_get_blocks(struct inode *inode, */ err = -EAGAIN; count = 0; + partial = chain + depth - 1; break; } blk = le32_to_cpu(*(chain[depth-1].p + count)); -- 2.1.4