netdev - Re: [PATCH net,v2 1/3] net: sched: cake: fix null pointer access issue when cake

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Message-ID: <874jw1bed9.fsf@toke.dk>
Date:   Tue, 18 Oct 2022 12:44:18 +0200
From:   Toke Høiland-Jørgensen <toke@...e.dk>
To:     Zhengchao Shao <shaozhengchao@...wei.com>,
        cake@...ts.bufferbloat.net, netdev@...r.kernel.org,
        jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Cc:     dave.taht@...il.com, weiyongjun1@...wei.com, yuehaibing@...wei.com,
        shaozhengchao@...wei.com
Subject: Re: [PATCH net,v2 1/3] net: sched: cake: fix null pointer access
 issue when cake_init() fails

Zhengchao Shao <shaozhengchao@...wei.com> writes:

> When the default qdisc is cake, if the qdisc of dev_queue fails to be
> inited during mqprio_init(), cake_reset() is invoked to clear
> resources. In this case, the tins is NULL, and it will cause gpf issue.
>
> The process is as follows:
> qdisc_create_dflt()
> 	cake_init()
> 		q->tins = kvcalloc(...)        --->failed, q->tins is NULL
> 	...
> 	qdisc_put()
> 		...
> 		cake_reset()
> 			...
> 			cake_dequeue_one()
> 				b = &q->tins[...]   --->q->tins is NULL
>
> The following is the Call Trace information:
> general protection fault, probably for non-canonical address
> 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> RIP: 0010:cake_dequeue_one+0xc9/0x3c0
> Call Trace:
> <TASK>
> cake_reset+0xb1/0x140
> qdisc_reset+0xed/0x6f0
> qdisc_destroy+0x82/0x4c0
> qdisc_put+0x9e/0xb0
> qdisc_create_dflt+0x2c3/0x4a0
> mqprio_init+0xa71/0x1760
> qdisc_create+0x3eb/0x1000
> tc_modify_qdisc+0x408/0x1720
> rtnetlink_rcv_msg+0x38e/0xac0
> netlink_rcv_skb+0x12d/0x3a0
> netlink_unicast+0x4a2/0x740
> netlink_sendmsg+0x826/0xcc0
> sock_sendmsg+0xc5/0x100
> ____sys_sendmsg+0x583/0x690
> ___sys_sendmsg+0xe8/0x160
> __sys_sendmsg+0xbf/0x160
> do_syscall_64+0x35/0x80
> entry_SYSCALL_64_after_hwframe+0x46/0xb0
> RIP: 0033:0x7f89e5122d04
> </TASK>
>
> Fixes: 046f6fd5daef ("sched: Add Common Applications Kept Enhanced (cake) qdisc")
> Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>

Acked-by: Toke Høiland-Jørgensen <toke@...e.dk>