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Subject: Re: [Linux-kernel-mentees] [PATCH] fs: fix KMSAN uninit-value bug by
 initializing nd in do_file_open_root
From:   Anant Thazhemadam <anant.thazhemadam@gmail.com>
To:     Al Viro <viro@zeniv.linux.org.uk>,
        Greg KH <gregkh@linuxfoundation.org>
Cc:     Eric Biggers <ebiggers@kernel.org>, linux-fsdevel@vger.kernel.org,
        linux-kernel-mentees@lists.linuxfoundation.org,
        syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com,
        linux-kernel@vger.kernel.org
References: <20200916052657.18683-1-anant.thazhemadam@gmail.com>
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 <20200919144451.GF2712238@kroah.com>
 <20200919161727.GG3421308@ZenIV.linux.org.uk>
 <20200919165558.GH3421308@ZenIV.linux.org.uk>
 <26d881e5-f68a-b3b7-4cb0-04a3c6c384ac@gmail.com>
Message-ID: <e8b218d4-e64a-ac0a-ea53-567d07a58f42@gmail.com>
Date:   Sun, 20 Sep 2020 01:47:39 +0530
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On 19-09-2020 17:03, Anant Thazhemadam wrote:
> On 19-09-2020 22:25, Al Viro wrote:
>> On Sat, Sep 19, 2020 at 05:17:27PM +0100, Al Viro wrote:
>>
>>> Lovely...  That would get an empty path and non-directory for a starting
>>> point, but it should end up with LAST_ROOT in nd->last_type.  Which should
>>> not be able to reach the readers of those fields...  Which kernel had
>>> that been on?
>> Yecchhh...  I see what's going on; I suspect that this ought to be enough.
>> Folks, could somebody test it on the original reproducer setup?
> Sure. I can do that.

Looks like this patch actually fixes this bug.
I made syzbot test the patch, and no issues were triggered!

Note:??? syzbot tested the patch with the KMSAN kernel, which
was recently rebased on v5.9-rc4.

Thanks,
Anant