syzbot

binder: undelivered TRANSACTION_ERROR: 29189
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BUG: KASAN: user-memory-access in atomic_sub_return include/asm-generic/atomic-instrumented.h:305 [inline]
BUG: KASAN: user-memory-access in dst_release net/core/dst.c:190 [inline]
BUG: KASAN: user-memory-access in dst_release+0x2a/0xb0 net/core/dst.c:185
Write of size 4 at addr 000000000001a494 by task kworker/u4:3/13552

CPU: 0 PID: 13552 Comm: kworker/u4:3 Not tainted 5.0.0+ #7
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+0x172/0x1f0 lib/dump_stack.c:113
 kasan_report.cold+0x5/0x40 mm/kasan/report.c:321
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_write+0x14/0x20 mm/kasan/common.c:106
 atomic_sub_return include/asm-generic/atomic-instrumented.h:305 [inline]
 dst_release net/core/dst.c:190 [inline]
 dst_release+0x2a/0xb0 net/core/dst.c:185
 dst_cache_destroy net/core/dst_cache.c:164 [inline]
 dst_cache_destroy+0xd3/0x1b0 net/core/dst_cache.c:156
 ipip6_dev_free+0x19/0x50 net/ipv6/sit.c:1355
 netdev_run_todo+0x51c/0x7d0 net/core/dev.c:8970
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:116
 sit_exit_batch_net+0x565/0x750 net/ipv6/sit.c:1891
 ops_exit_list.isra.0+0x105/0x160 net/core/net_namespace.c:156
 cleanup_net+0x3fb/0x960 net/core/net_namespace.c:551
 process_one_work+0x98e/0x1790 kernel/workqueue.c:2173
 worker_thread+0x98/0xe40 kernel/workqueue.c:2319
 kthread+0x357/0x430 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
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