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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 15 Nov 2022 07:12:24 +0100
Message-ID: <CACT4Y+bD72vupKkvnbCH8KxVH3wmu7frNj0ycfCE0SK+CxjeZw@mail.gmail.com>
Subject: Re: [syzbot] KASAN: use-after-free Read in kernfs_activate (2)
To:     Tejun Heo <tj@kernel.org>
Cc:     syzbot <syzbot+782984d6f1701b526edb@syzkaller.appspotmail.com>,
        gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
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On Mon, 14 Nov 2022 at 22:42, Tejun Heo <tj@kernel.org> wrote:
>
> On Sun, Nov 13, 2022 at 07:40:56AM -0800, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    59f2f4b8a757 fs/userfaultfd: Fix maple tree iterator in us..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=14e836fa880000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=480ba0fb2fd243ac
> > dashboard link: https://syzkaller.appspot.com/bug?extid=782984d6f1701b526edb
> > compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/619de907b82c/disk-59f2f4b8.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/bcd0dc7d69ef/vmlinux-59f2f4b8.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/a8dbe0bc7228/bzImage-59f2f4b8.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+782984d6f1701b526edb@syzkaller.appspotmail.com
> >
> > usb 4-1: Direct firmware load for ueagle-atm/eagleII.fw failed with error -2
> > usb 4-1: Falling back to sysfs fallback for: ueagle-atm/eagleII.fw
> > ==================================================================
> > BUG: KASAN: use-after-free in kernfs_root fs/kernfs/kernfs-internal.h:66 [inline]
> > BUG: KASAN: use-after-free in kernfs_next_descendant_post fs/kernfs/dir.c:1289 [inline]
> > BUG: KASAN: use-after-free in kernfs_activate+0xd0/0x3a0 fs/kernfs/dir.c:1344
> > Read of size 8 at addr ffff888079194b10 by task kworker/1:12/5383
>
> Likely the same one as:
>
>  http://lkml.kernel.org/r/0000000000003a95ce05cd867417@google.com
>
> This is a bug on the firmware loader side.

#syz dup: KASAN: use-after-free Read in kernfs_next_descendant_post (2)