linux-kernel - Re: [PATCH -next 0/5] fs: fix possible null-ptr-deref when parsing param

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]

Message-ID: <f81f0ddc-cff3-b327-f4b2-57102bdf0ecf@themaw.net>
Date:   Tue, 1 Nov 2022 08:32:26 +0800
From:   Ian Kent <raven@...maw.net>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Hawkins Jiawei <yin31149@...il.com>, viro@...iv.linux.org.uk
Cc:     18801353760@....com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        cmaiolino@...hat.com, dhowells@...hat.com, hughd@...gle.com,
        miklos@...redi.hu, oliver.sang@...el.com, siddhesh@...plt.org,
        syzbot+db1d2ea936378be0e4ea@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, tytso@....edu, smfrench@...il.com,
        pc@....nz, lsahlber@...hat.com, sprasad@...rosoft.com,
        tom@...pey.com
Subject: Re: [PATCH -next 0/5] fs: fix possible null-ptr-deref when parsing
 param


On 31/10/22 19:28, Tetsuo Handa wrote:
> On 2022/10/24 12:34, Ian Kent wrote:
>> On 24/10/22 08:42, Hawkins Jiawei wrote:
>>> On Mon, 24 Oct 2022 at 00:48, Al Viro <viro@...iv.linux.org.uk> wrote:
>>>> On Mon, Oct 24, 2022 at 12:39:41AM +0800, Hawkins Jiawei wrote:
>>>>> According to commit "vfs: parse: deal with zero length string value",
>>>>> kernel will set the param->string to null pointer in vfs_parse_fs_string()
>>>>> if fs string has zero length.
>>>>>
>>>>> Yet the problem is that, when fs parses its mount parameters, it will
>>>>> dereferences the param->string, without checking whether it is a
>>>>> null pointer, which may trigger a null-ptr-deref bug.
>>>>>
>>>>> So this patchset reviews all functions for fs to parse parameters,
>>>>> by using `git grep -n "\.parse_param" fs/*`, and adds sanity check
>>>>> on param->string if its function will dereference param->string
>>>>> without check.
>>>> How about reverting the commit in question instead?  Or dropping it
>>>> from patch series, depending upon the way akpm handles the pile
>>>> these days...
>>> I think both are OK.
>>>
>>> On one hand, commit "vfs: parse: deal with zero length string value"
>>> seems just want to make output more informattive, which probably is not
>>> the one which must be applied immediately to fix the
>>> panic.
>>>
>>> On the other hand, commit "vfs: parse: deal with zero length string value"
>>> affects so many file systems, so there are probably some deeper
>>> null-ptr-deref bugs I ignore, which may take time to review.
>> Yeah, it would be good to make the file system handling consistent
>> but I think there's been a bit too much breakage and it appears not
>> everyone thinks the approach is the right way to do it.
>>
>> I'm thinking of abandoning this and restricting it to the "source"
>> parameter only to solve the user space mount table parser problem but
>> still doing it in the mount context code to keep it general (at least
>> for this case).
> No progress on this problem, and syzbot is reporting one after the other...
>
> I think that reverting is the better choice.

Yes, I agree/


Ian