linux-ext4 - Re: [PATCH] ext4: do not use extent after put

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Fri, 30 Oct 2020 09:23:38 +0800
From:   yangerkun <yangerkun@...wei.com>
To:     Ritesh Harjani <riteshh@...ux.ibm.com>, <adilger@...ger.ca>
CC:     <tytso@....edu>, <jack@...e.com>, <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: do not use extent after put_bh



在 2020/10/30 0:08, Ritesh Harjani 写道:
> 
> 
> On 10/28/20 11:26 AM, yangerkun wrote:
>> ext4_ext_search_right will read more extent block and call put_bh after
>> we get the information we need. However ret_ex will break this and may
>> cause use-after-free once pagecache has been freed. Fix it by dup the
>> extent we need.
> 
> 
> It would be good if we have a test case to reproduce it. Do you?
> Ideally it should go in fstests, if you have some way to forcefully
> reproduce it/simulate it. Let me know, if needed, I can as well help to
> get those into fstests.

Sorry for that. I found this bug while reading source code. Not with a 
testcase.

And time leave for drop pagecache is so small(time between 
get_implied_cluster_alloc and ext4_ext_search_right in 
ext4_ext_map_blocks, other caller for ext4_ext_search_right won't use 
@ret_ex). It may difficult to reproduce it expect a delay injection.

Thanks,
Kun.

> 
> -ritesh
> .