KASAN: use-after-free Read in route4_destroy

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 93556fb2 Linux 4.19.111
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16f87489e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a67891b0f95addd
dashboard link: https://syzkaller.appspot.com/bug?extid=d635517d87f68b20722c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d63551...@syzkaller.appspotmail.com

device veth0_macvtap left promiscuous mode
device veth1_vlan left promiscuous mode
device veth0_vlan left promiscuous mode
NOHZ: local_softirq_pending 08
==================================================================
BUG: KASAN: use-after-free in route4_destroy+0x698/0x7e0 net/sched/cls_route.c:298
Read of size 8 at addr ffff888090f9f900 by task kworker/u4:1/23

CPU: 0 PID: 23 Comm: kworker/u4:1 Not tainted 4.19.111-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
route4_destroy+0x698/0x7e0 net/sched/cls_route.c:298
tcf_proto_destroy+0x5d/0xe0 net/sched/cls_api.c:190
tcf_chain_flush+0x1ed/0x330 net/sched/cls_api.c:362
tcf_block_put_ext.part.0+0x418/0x9a0 net/sched/cls_api.c:770
tcf_block_put_ext net/sched/cls_api.c:754 [inline]
tcf_block_put+0xad/0xf8 net/sched/cls_api.c:797
hfsc_destroy_qdisc+0xe0/0x280 net/sched/sch_hfsc.c:1509
qdisc_destroy+0x17c/0x6b0 net/sched/sch_generic.c:982
dev_shutdown+0x2b5/0x47a net/sched/sch_generic.c:1300
rollback_registered_many+0x64a/0xc40 net/core/dev.c:8173
unregister_netdevice_many.part.0+0x16/0x1e0 net/core/dev.c:9294
unregister_netdevice_many net/core/dev.c:9293 [inline]
default_device_exit_batch+0x2ff/0x3c0 net/core/dev.c:9765
ops_exit_list.isra.0+0xef/0x140 net/core/net_namespace.c:156
cleanup_net+0x3bf/0x850 net/core/net_namespace.c:553
process_one_work+0x91f/0x1640 kernel/workqueue.c:2155
worker_thread+0x96/0xe20 kernel/workqueue.c:2298
kthread+0x34a/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 17437:
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc mm/kasan/kasan.c:553 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
kmem_cache_alloc_trace+0x14d/0x7a0 mm/slab.c:3625
kmalloc include/linux/slab.h:515 [inline]
kzalloc include/linux/slab.h:709 [inline]
kthread+0x96/0x420 kernel/kthread.c:215
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Freed by task 13207:
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
__cache_free mm/slab.c:3503 [inline]
kfree+0xce/0x220 mm/slab.c:3822
free_task+0xe3/0x110 kernel/fork.c:420
__put_task_struct+0x1fc/0x4b0 kernel/fork.c:694
put_task_struct include/linux/sched/task.h:98 [inline]
delayed_put_task_struct+0x1e3/0x330 kernel/exit.c:181
__rcu_reclaim kernel/rcu/rcu.h:236 [inline]
rcu_do_batch kernel/rcu/tree.c:2584 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2897 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:2864 [inline]
rcu_process_callbacks+0xb2d/0x17f0 kernel/rcu/tree.c:2881
__do_softirq+0x26c/0x93c kernel/softirq.c:292

The buggy address belongs to the object at ffff888090f9f900
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes inside of
192-byte region [ffff888090f9f900, ffff888090f9f9c0)
The buggy address belongs to the page:
page:ffffea000243e7c0 count:1 mapcount:0 mapping:ffff88812c3dc040 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea0002017888 ffffea00025c9688 ffff88812c3dc040
raw: 0000000000000000 ffff888090f9f000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888090f9f800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888090f9f880: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff888090f9f900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888090f9f980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888090f9fa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.