linux-kernel - Re: [syzbot] [net?] KASAN: null-ptr-deref Write in rcuref

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Message-ID: <6891ec2a.050a0220.7f033.0021.GAE@google.com>
Date: Tue, 05 Aug 2025 04:34:02 -0700
From: syzbot <syzbot+27d7cfbc93457e472e00@...kaller.appspotmail.com>
To: atenart@...nel.org, davem@...emloft.net, dawid.osuchowski@...ux.intel.com, 
	edumazet@...gle.com, gal@...dia.com, horms@...nel.org, kuba@...nel.org, 
	kuniyu@...gle.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] KASAN: null-ptr-deref Write in rcuref_put (4)

syzbot has bisected this issue to:

commit de9c4861fb42f0cd72da844c3c34f692d5895b7b
Author: Eric Dumazet <edumazet@...gle.com>
Date:   Tue Jul 29 08:02:07 2025 +0000

    pptp: ensure minimal skb length in pptp_xmit()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17cb2042580000
start commit:   5c5a10f0be96 Add linux-next specific files for 20250804
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=142b2042580000
console output: https://syzkaller.appspot.com/x/log.txt?x=102b2042580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f4ccbd076877954b
dashboard link: https://syzkaller.appspot.com/bug?extid=27d7cfbc93457e472e00
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1628faa2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12490434580000

Reported-by: syzbot+27d7cfbc93457e472e00@...kaller.appspotmail.com
Fixes: de9c4861fb42 ("pptp: ensure minimal skb length in pptp_xmit()")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection