netdev - Re: [PATCH] rose: Fix NULL pointer dereference in rose_send

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Date:   Sat, 5 Nov 2022 20:07:02 +0100
From:   F6BVP <f6bvp@...e.fr>
To:     Zhang Qilong <zhangqilong3@...wei.com>, ralf@...ux-mips.org,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Cc:     linux-hams@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] rose: Fix NULL pointer dereference in rose_send_frame()

ZhangQilong ni hao,

I have just pulled net-next 6.1.0-rc3 including  the rose_link.c patch 
on my FPAC/ROSE hamradio node F6BVP.

Xie xie ni

Zaitien

Bernard,

http://f6bvp.org

Le 28/10/2022 à 18:10, Zhang Qilong a écrit :
> The syzkaller reported an issue:
>
> KASAN: null-ptr-deref in range [0x0000000000000380-0x0000000000000387]
> CPU: 0 PID: 4069 Comm: kworker/0:15 Not tainted 6.0.0-syzkaller-02734-g0326074ff465 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> Workqueue: rcu_gp srcu_invoke_callbacks
> RIP: 0010:rose_send_frame+0x1dd/0x2f0 net/rose/rose_link.c:101
> Call Trace:
>   <IRQ>
>   rose_transmit_clear_request+0x1d5/0x290 net/rose/rose_link.c:255
>   rose_rx_call_request+0x4c0/0x1bc0 net/rose/af_rose.c:1009
>   rose_loopback_timer+0x19e/0x590 net/rose/rose_loopback.c:111
>   call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474
>   expire_timers kernel/time/timer.c:1519 [inline]
>   __run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790
>   __run_timers kernel/time/timer.c:1768 [inline]
>   run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803
>   __do_softirq+0x1d0/0x9c8 kernel/softirq.c:571
>   [...]
>   </IRQ>
>
> It triggers NULL pointer dereference when 'neigh->dev->dev_addr' is
> called in the rose_send_frame(). It's the first occurrence of the
> `neigh` is in rose_loopback_timer() as `rose_loopback_neigh', and
> the 'dev' in 'rose_loopback_neigh' is initialized sa nullptr.
>
> It had been fixed by commit 3b3fd068c56e3fbea30090859216a368398e39bf
> ("rose: Fix Null pointer dereference in rose_send_frame()") ever.
> But it's introduced by commit 3c53cd65dece47dd1f9d3a809f32e59d1d87b2b8
> ("rose: check NULL rose_loopback_neigh->loopback") again.
>
> We fix it by add NULL check in rose_transmit_clear_request(). When
> the 'dev' in 'neigh' is NULL, we don't reply the request and just
> clear it.
>
> syzkaller don't provide repro, and I provide a syz repro like:
> r0 = syz_init_net_socket$bt_sco(0x1f, 0x5, 0x2)
> ioctl$sock_inet_SIOCSIFFLAGS(r0, 0x8914, &(0x7f0000000180)={'rose0\x00', 0x201})
> r1 = syz_init_net_socket$rose(0xb, 0x5, 0x0)
> bind$rose(r1, &(0x7f00000000c0)=@...l={0xb, @dev, @null, 0x0, [@null, @null, @netrom, @netrom, @default, @null]}, 0x40)
> connect$rose(r1, &(0x7f0000000240)=@...rt={0xb, @dev={0xbb, 0xbb, 0xbb, 0x1, 0x0}, @remote={0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0x1}, 0x1, @netrom={0xbb, 0xbb, 0xbb, 0xbb, 0xbb, 0x0, 0x0}}, 0x1c)
>
> Fixes: 3c53cd65dece ("rose: check NULL rose_loopback_neigh->loopback")
> Signed-off-by: Zhang Qilong <zhangqilong3@...wei.com>
> ---
>   net/rose/rose_link.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/net/rose/rose_link.c b/net/rose/rose_link.c
> index 8b96a56d3a49..0f77ae8ef944 100644
> --- a/net/rose/rose_link.c
> +++ b/net/rose/rose_link.c
> @@ -236,6 +236,9 @@ void rose_transmit_clear_request(struct rose_neigh *neigh, unsigned int lci, uns
>   	unsigned char *dptr;
>   	int len;
>   
> +	if (!neigh->dev)
> +		return;
> +
>   	len = AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + ROSE_MIN_LEN + 3;
>   
>   	if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)