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BUG: KASAN: use-after-free in route4_get+0x3e1/0x420 net/sched/cls_route.c:235
Read of size 4 at addr ffff88809f861740 by task syz-executor.0/8687

CPU: 0 PID: 8687 Comm: syz-executor.0 Not tainted 5.6.0-next-20200411-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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:382
 __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 route4_get+0x3e1/0x420 net/sched/cls_route.c:235
 tc_new_tfilter+0x7a9/0x20b0 net/sched/cls_api.c:2147
 rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5445
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
 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+0x6bf/0x7e0 net/socket.c:2362
 ___sys_sendmsg+0x100/0x170 net/socket.c:2416
 __sys_sendmsg+0xec/0x1b0 net/socket.c:2449
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c889
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f3098620c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f30986216d4 RCX: 000000000045c889
RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000007
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009fd R14: 00000000004ccb8d R15: 000000000076bfac

Allocated by task 8682:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:468
 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+0x2a8/0x2270 net/sched/cls_route.c:493
 tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2168
 rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5445
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
 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+0x6bf/0x7e0 net/socket.c:2362
 ___sys_sendmsg+0x100/0x170 net/socket.c:2416
 __sys_sendmsg+0xec/0x1b0 net/socket.c:2449
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 40:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:456
 __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+0x965/0x16a0 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88809f861700
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 64 bytes inside of
 192-byte region [ffff88809f861700, ffff88809f8617c0)
The buggy address belongs to the page:
page:ffffea00027e1840 refcount:1 mapcount:0 mapping:000000000b2f9698 index:0xffff88809f861100
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000241a008 ffffea0002920048 ffff8880aa000000
raw: ffff88809f861100 ffff88809f861000 000000010000000e 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809f861600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88809f861680: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc
>ffff88809f861700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88809f861780: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88809f861800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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