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SubjectKASAN: use-after-free Read in route4_destroy
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Hello,

syzbot found the following crash on:

HEAD commit: fb33c651 Linux 5.6-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1394f7c3e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9f894bd92023de02
dashboard link: https://syzkaller.appspot.com/bug?extid=703474f5b80cd91649bc
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1397ffdde00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13cb20e5e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+703474f5b80cd91649bc@syzkaller.appspotmail.com

tipc: TX() has been purged, node left!
==================================================================
BUG: KASAN: use-after-free in route4_destroy+0x6bf/0x800 net/sched/cls_route.c:295
Read of size 8 at addr ffff888022eab800 by task kworker/u16:0/8

CPU: 3 PID: 8 Comm: kworker/u16:0 Not tainted 5.6.0-rc6-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
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.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
__kasan_report.cold+0x1a/0x32 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:641
route4_destroy+0x6bf/0x800 net/sched/cls_route.c:295
tcf_proto_destroy+0x6e/0x310 net/sched/cls_api.c:296
tcf_proto_put+0x8c/0xc0 net/sched/cls_api.c:308
tcf_chain_flush+0x266/0x390 net/sched/cls_api.c:600
tcf_block_flush_all_chains net/sched/cls_api.c:1052 [inline]
__tcf_block_put+0x1a4/0x540 net/sched/cls_api.c:1214
tcf_block_put_ext net/sched/cls_api.c:1414 [inline]
tcf_block_put+0xb3/0x100 net/sched/cls_api.c:1429
hfsc_destroy_qdisc+0xe0/0x280 net/sched/sch_hfsc.c:1501
qdisc_destroy+0x118/0x690 net/sched/sch_generic.c:958
qdisc_put+0xcd/0xe0 net/sched/sch_generic.c:985
dev_shutdown+0x2b5/0x486 net/sched/sch_generic.c:1311
rollback_registered_many+0x603/0xe70 net/core/dev.c:8803
unregister_netdevice_many.part.0+0x16/0x1e0 net/core/dev.c:9966
unregister_netdevice_many net/core/dev.c:9965 [inline]
default_device_exit_batch+0x311/0x3d0 net/core/dev.c:10442
ops_exit_list.isra.0+0x103/0x150 net/core/net_namespace.c:175
cleanup_net+0x511/0xa50 net/core/net_namespace.c:589
process_one_work+0x94b/0x1690 kernel/workqueue.c:2266
worker_thread+0x96/0xe20 kernel/workqueue.c:2412
kthread+0x357/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 8791:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
route4_change+0x2a9/0x2250 net/sched/cls_route.c:493
tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2103
rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
___sys_sendmsg+0x100/0x170 net/socket.c:2397
__sys_sendmsg+0xec/0x1b0 net/socket.c:2430
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/common.c:476
__cache_free mm/slab.c:3426 [inline]
kfree+0x109/0x2b0 mm/slab.c:3757
route4_delete_filter_work+0x17/0x20 net/sched/cls_route.c:266
process_one_work+0x94b/0x1690 kernel/workqueue.c:2266
worker_thread+0x96/0xe20 kernel/workqueue.c:2412
kthread+0x357/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff888022eab800
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes inside of
192-byte region [ffff888022eab800, ffff888022eab8c0)
The buggy address belongs to the page:
page:ffffea00008baac0 refcount:1 mapcount:0 mapping:ffff88802cc00000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0000a95b08 ffffea00008a6fc8 ffff88802cc00000
raw: 0000000000000000 ffff888022eab000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888022eab700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888022eab780: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff888022eab800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888022eab880: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888022eab900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
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syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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