syzbot

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BUG: KASAN: use-after-free in rds_tcp_tune+0x491/0x520 net/rds/tcp.c:397
Read of size 4 at addr ffff8801cd6a20d8 by task kworker/u4:1/21

CPU: 0 PID: 21 Comm: kworker/u4:1 Not tainted 4.15.0-rc8-next-20180119+ #102
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: krdsd rds_connect_worker
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 rds_tcp_tune+0x491/0x520 net/rds/tcp.c:397
 rds_tcp_conn_path_connect+0x397/0x940 net/rds/tcp_connect.c:113
 rds_connect_worker+0x156/0x1f0 net/rds/threads.c:175
 process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
 worker_thread+0x223/0x1990 kernel/workqueue.c:2247
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

Allocated by task 3670:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 __do_kmalloc mm/slab.c:3705 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3714
IPv6: ADDRCONF(NETDEV_UP): bridge0: link is not ready
 kmalloc include/linux/slab.h:517 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 ops_init+0x172/0x570 net/core/net_namespace.c:108
 setup_net+0x313/0x710 net/core/net_namespace.c:302
 copy_net_ns+0x238/0x580 net/core/net_namespace.c:426
 create_new_namespaces+0x425/0x880 kernel/nsproxy.c:107
 unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:206
 SYSC_unshare kernel/fork.c:2415 [inline]
 SyS_unshare+0x653/0xfa0 kernel/fork.c:2365
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 298:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kfree+0xd9/0x260 mm/slab.c:3800
 ops_free net/core/net_namespace.c:132 [inline]
 ops_free_list.part.8+0x27e/0x3e0 net/core/net_namespace.c:154
 ops_free_list net/core/net_namespace.c:152 [inline]
 cleanup_net+0x665/0xb50 net/core/net_namespace.c:495
 process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
 worker_thread+0x223/0x1990 kernel/workqueue.c:2247
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

The buggy address belongs to the object at ffff8801cd6a2080
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 88 bytes inside of
 96-byte region [ffff8801cd6a2080, ffff8801cd6a20e0)
The buggy address belongs to the page:
page:ffffea000735a880 count:1 mapcount:0 mapping:ffff8801cd6a2000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cd6a2000 0000000000000000 0000000100000020
raw: ffffea000736a260 ffffea00072662a0 ffff8801dac004c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cd6a1f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801cd6a2000: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff8801cd6a2080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                                    ^
 ffff8801cd6a2100: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8801cd6a2180: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
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