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To: Zhengchao Shao <shaozhengchao@huawei.com>, cake@lists.bufferbloat.net,
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Cc: dave.taht@gmail.com, weiyongjun1@huawei.com, yuehaibing@huawei.com,
 shaozhengchao@huawei.com
In-Reply-To: <20221018063201.306474-2-shaozhengchao@huawei.com>
References: <20221018063201.306474-1-shaozhengchao@huawei.com>
 <20221018063201.306474-2-shaozhengchao@huawei.com>
Date: Tue, 18 Oct 2022 12:44:18 +0200
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Subject: Re: [Cake] [PATCH net,
 v2 1/3] net: sched: cake: fix null pointer access issue when
 cake_init() fails
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Zhengchao Shao <shaozhengchao@huawei.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 =3D kvcalloc(...)        --->failed, q->tins is NULL
> 	...
> 	qdisc_put()
> 		...
> 		cake_reset()
> 			...
> 			cake_dequeue_one()
> 				b =3D &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@huawei.com>

Acked-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk>