Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 19 Oct 2022 15:30:18 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     syzbot <syzbot+81c4b4bbba6eea2cfcae@syzkaller.appspotmail.com>
Cc:     andrew@lunn.ch, bagasdotme@gmail.com, davem@davemloft.net,
        edumazet@google.com, linux-kernel@vger.kernel.org,
        linux@rempel-privat.de, lkp@intel.com, netdev@vger.kernel.org,
        pabeni@redhat.com, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] general protection fault in pse_prepare_data
Message-ID: <20221019153018.2ca0580d@kernel.org>
In-Reply-To: <00000000000044139d05eb617b1c@google.com>
References: <00000000000044139d05eb617b1c@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Wed, 19 Oct 2022 04:26:35 -0700 syzbot wrote:
> HEAD commit:    55be6084c8e0 Merge tag 'timers-core-2022-10-05' of git://g..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=140d5a2c880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df75278aabf0681a
> dashboard link: https://syzkaller.appspot.com/bug?extid=81c4b4bbba6eea2cfcae
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13470244880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=146e88b4880000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/9d967e5d91fa/disk-55be6084.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/9a8cffcbc089/vmlinux-55be6084.xz
> 
> Bisection is inconclusive: the first bad commit could be any of:
> 
> 331834898f2b Merge branch 'add-generic-pse-support'
> 66741b4e94ca net: pse-pd: add regulator based PSE driver
> 2a4187f4406e once: rename _SLOW to _SLEEPABLE
> f05dfdaf567a dt-bindings: net: pse-dt: add bindings for regulator based PoDL PSE controller
> 18ff0bcda6d1 ethtool: add interface to interact with Ethernet Power Equipment
> e52f7c1ddf3e Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
> 681bf011b9b5 eth: pse: add missing static inlines
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11fc42b4880000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+81c4b4bbba6eea2cfcae@syzkaller.appspotmail.com
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000008: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000040-0x0000000000000047]
> CPU: 1 PID: 3609 Comm: syz-executor227 Not tainted 6.0.0-syzkaller-09589-g55be6084c8e0 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> RIP: 0010:pse_prepare_data+0x66/0x1e0 net/ethtool/pse-pd.c:67

Yeah, looking at ethtool internals - info can be NULL :(

For reasons I haven't quite grasped yet myself we use a different
structure for info on do and dump which makes getting to extack in
generic code inconvenient.