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Sender: Tejun Heo <htejun@gmail.com>
Date:   Mon, 14 Nov 2022 11:42:47 -1000
From:   Tejun Heo <tj@kernel.org>
To:     syzbot <syzbot+782984d6f1701b526edb@syzkaller.appspotmail.com>
Cc:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Read in kernfs_activate (2)
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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.

Thanks.

-- 
tejun