net: sched: cake: fix null pointer access issue when cake_init() fails

In the Linux kernel, the following vulnerability has been resolved:

net: sched: cake: fix null pointer access issue when cake_init() fails

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>