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BUG: KCSAN: data-race in dst_alloc / percpu_counter_add_batch

write to 0xffff8880a654d048 of 8 bytes by interrupt on cpu 0:
 percpu_counter_add_batch+0xca/0x150 lib/percpu_counter.c:91
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 dst_entries_add include/net/dst_ops.h:58 [inline]
 dst_destroy+0x1df/0x210 net/core/dst.c:117
 dst_destroy_rcu+0x1f/0x30 net/core/dst.c:142
 rcu_do_batch kernel/rcu/tree.c:2206 [inline]
 rcu_core+0x533/0x9f0 kernel/rcu/tree.c:2433
 rcu_core_si+0x12/0x20 kernel/rcu/tree.c:2442
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 run_ksoftirqd+0x46/0x60 kernel/softirq.c:603
 smpboot_thread_fn+0x37d/0x4a0 kernel/smpboot.c:165
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880a654d048 of 8 bytes by task 1845 on cpu 1:
 dst_entries_get_fast include/net/dst_ops.h:48 [inline]
 dst_alloc+0x55/0x149 net/core/dst.c:84
 ip6_dst_alloc+0x3d/0x80 net/ipv6/route.c:355
 ip6_rt_cache_alloc+0x12b/0x480 net/ipv6/route.c:1344
 ip6_pol_route+0x5d2/0x730 net/ipv6/route.c:2223
 ip6_pol_route_output+0x48/0x60 net/ipv6/route.c:2455
 fib6_rule_lookup+0x3d6/0x470 net/ipv6/fib6_rules.c:118
 ip6_route_output_flags_noref+0x16b/0x230 net/ipv6/route.c:2487
 ip6_route_output_flags+0x50/0x1a0 net/ipv6/route.c:2500
 ip6_dst_lookup_tail+0x25d/0xc50 net/ipv6/ip6_output.c:1052
 ip6_dst_lookup_flow+0x5c/0x110 net/ipv6/ip6_output.c:1153
 rawv6_sendmsg+0x9be/0x2340 net/ipv6/raw.c:928
 inet_sendmsg+0x6d/0x90 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:672
 ____sys_sendmsg+0x212/0x4d0 net/socket.c:2343
 ___sys_sendmsg+0xb5/0x100 net/socket.c:2397
 __sys_sendmmsg+0x123/0x350 net/socket.c:2487
 __do_sys_sendmmsg net/socket.c:2516 [inline]
 __se_sys_sendmmsg net/socket.c:2513 [inline]
 __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2513
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1845 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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