net/sched: sch_taprio: fix possible use-after-free

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

net/sched: sch_taprio: fix possible use-after-free

syzbot reported a nasty crash [1] in net_tx_action() which

made little sense until we got a repro.

This repro installs a taprio qdisc, but providing an

invalid TCA_RATE attribute.

qdisc_create() has to destroy the just initialized

taprio qdisc, and taprio_destroy() is called.

However, the hrtimer used by taprio had already fired,

therefore advance_sched() called __netif_schedule().

Then net_tx_action was trying to use a destroyed qdisc.

We can not undo the __netif_schedule(), so we must wait

until one cpu serviced the qdisc before we can proceed.

Many thanks to Alexander Potapenko for his help.

[1]

BUG: KMSAN: uninit-value in queued_spin_trylock include/asm-generic/qspinlock.h:94 [inline]

BUG: KMSAN: uninit-value in do_raw_spin_trylock include/linux/spinlock.h:191 [inline]

BUG: KMSAN: uninit-value in __raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline]

BUG: KMSAN: uninit-value in _raw_spin_trylock+0x92/0xa0 kernel/locking/spinlock.c:138

queued_spin_trylock include/asm-generic/qspinlock.h:94 [inline]

do_raw_spin_trylock include/linux/spinlock.h:191 [inline]

__raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline]

_raw_spin_trylock+0x92/0xa0 kernel/locking/spinlock.c:138

spin_trylock include/linux/spinlock.h:359 [inline]

qdisc_run_begin include/net/sch_generic.h:187 [inline]

qdisc_run+0xee/0x540 include/net/pkt_sched.h:125

net_tx_action+0x77c/0x9a0 net/core/dev.c:5086

__do_softirq+0x1cc/0x7fb kernel/softirq.c:571

run_ksoftirqd+0x2c/0x50 kernel/softirq.c:934

smpboot_thread_fn+0x554/0x9f0 kernel/smpboot.c:164

kthread+0x31b/0x430 kernel/kthread.c:376

ret_from_fork+0x1f/0x30

Uninit was created at:

slab_post_alloc_hook mm/slab.h:732 [inline]

slab_alloc_node mm/slub.c:3258 [inline]

__kmalloc_node_track_caller+0x814/0x1250 mm/slub.c:4970

kmalloc_reserve net/core/skbuff.c:358 [inline]

__alloc_skb+0x346/0xcf0 net/core/skbuff.c:430

alloc_skb include/linux/skbuff.h:1257 [inline]

nlmsg_new include/net/netlink.h:953 [inline]

netlink_ack+0x5f3/0x12b0 net/netlink/af_netlink.c:2436

netlink_rcv_skb+0x55d/0x6c0 net/netlink/af_netlink.c:2507

rtnetlink_rcv+0x30/0x40 net/core/rtnetlink.c:6108

netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]

netlink_unicast+0xf3b/0x1270 net/netlink/af_netlink.c:1345

netlink_sendmsg+0x1288/0x1440 net/netlink/af_netlink.c:1921

sock_sendmsg_nosec net/socket.c:714 [inline]

sock_sendmsg net/socket.c:734 [inline]

____sys_sendmsg+0xabc/0xe90 net/socket.c:2482

___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2536

__sys_sendmsg net/socket.c:2565 [inline]

__do_sys_sendmsg net/socket.c:2574 [inline]

__se_sys_sendmsg net/socket.c:2572 [inline]

__x64_sys_sendmsg+0x367/0x540 net/socket.c:2572

do_syscall_x64 arch/x86/entry/common.c:50 [inline]

do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80

entry_SYSCALL_64_after_hwframe+0x63/0xcd

CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 6.0.0-rc2-syzkaller-47461-gac3859c02d7f #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022