linux-kernel - Re: [syzbot] KMSAN: uninit-value in make

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Date:   Sat, 11 Dec 2021 11:05:40 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     syzbot <syzbot+ce39644883793043ee77@...kaller.appspotmail.com>
Cc:     akpm@...ux-foundation.org, cxfcosmos@...il.com,
        ebiederm@...ssion.com, glider@...gle.com, legion@...nel.org,
        linux-kernel@...r.kernel.org, serge@...lyn.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KMSAN: uninit-value in make_kuid

On Fri, Dec 10, 2021 at 04:59:26AM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    b0f85c4ccdd4 kmsan: report: add dump_stack_print_info()
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=1704eaf9b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e00a8959fdd3f3e8
> dashboard link: https://syzkaller.appspot.com/bug?extid=ce39644883793043ee77
> compiler:       clang version 14.0.0 (git@...hub.com:llvm/llvm-project.git 0996585c8e3b3d409494eb5f1cad714b9e1f7fb5), GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ce39644883793043ee77@...kaller.appspotmail.com

I think this is triggered by the same 9p bug where it copies
uninitialized memory during setattr and then proceeds to send that
uninitialized memory over the wire. A patch for this was sent to 9p
devel but it seems to not have made it into mainline or -next just yet:
https://sourceforge.net/p/v9fs/mailman/message/37392685/