IPVS: ftp: loaded support on port[0] = 21
==================================================================
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_unless include/linux/atomic.h:575 [inline]
BUG: KASAN: use-after-free in atomic_add_unless include/linux/atomic.h:597 [inline]
BUG: KASAN: use-after-free in dst_hold_safe include/net/dst.h:308 [inline]
BUG: KASAN: use-after-free in ip6_hold_safe+0xa7/0x3a0 net/ipv6/route.c:1023
Read of size 4 at addr ffff88808cbb286c by task syz-executor.1/2274

CPU: 1 PID: 2274 Comm: syz-executor.1 Not tainted 5.0.0-rc7+ #76
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+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_read+0x11/0x20 mm/kasan/common.c:100
 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
 atomic_fetch_add_unless include/linux/atomic.h:575 [inline]
 atomic_add_unless include/linux/atomic.h:597 [inline]
 dst_hold_safe include/net/dst.h:308 [inline]
 ip6_hold_safe+0xa7/0x3a0 net/ipv6/route.c:1023
 rt6_get_pcpu_route net/ipv6/route.c:1243 [inline]
 ip6_pol_route+0x33d/0xf00 net/ipv6/route.c:1892
 ip6_pol_route_input+0x65/0x80 net/ipv6/route.c:1911
 fib6_rule_lookup+0x26b/0x560 net/ipv6/fib6_rules.c:122
 ip6_route_input_lookup+0xb7/0xd0 net/ipv6/route.c:1923
 ip6_route_input+0x5e6/0x9e0 net/ipv6/route.c:2058
 ip6_rcv_finish_core.isra.0+0x174/0x590 net/ipv6/ip6_input.c:63
 ip6_rcv_finish+0x17d/0x320 net/ipv6/ip6_input.c:74
 NF_HOOK include/linux/netfilter.h:289 [inline]
 NF_HOOK include/linux/netfilter.h:283 [inline]
 ipv6_rcv+0x10e/0x420 net/ipv6/ip6_input.c:272
 __netif_receive_skb_one_core+0x115/0x1a0 net/core/dev.c:4973
 __netif_receive_skb+0x2c/0x1c0 net/core/dev.c:5083
 netif_receive_skb_internal+0x117/0x660 net/core/dev.c:5186
 napi_frags_finish net/core/dev.c:5753 [inline]
 napi_gro_frags+0xade/0xd10 net/core/dev.c:5827
 tun_get_user+0x28ae/0x3b20 drivers/net/tun.c:1974
 tun_chr_write_iter+0xbd/0x160 drivers/net/tun.c:2019
 call_write_iter include/linux/fs.h:1863 [inline]
 do_iter_readv_writev+0x5e0/0x8e0 fs/read_write.c:680
 do_iter_write fs/read_write.c:956 [inline]
 do_iter_write+0x184/0x610 fs/read_write.c:937
 vfs_writev+0x1b3/0x2f0 fs/read_write.c:1001
 do_writev+0xf6/0x290 fs/read_write.c:1036
 __do_sys_writev fs/read_write.c:1109 [inline]
 __se_sys_writev fs/read_write.c:1106 [inline]
 __x64_sys_writev+0x75/0xb0 fs/read_write.c:1106
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ce1
Code: 75 14 b8 14 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 e4 b9 fb ff c3 48 83 ec 08 e8 1a 2d 00 00 48 89 04 24 b8 14 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 63 2d 00 00 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007fc5d072aba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0000000000000052 RCX: 0000000000457ce1
RDX: 0000000000000001 RSI: 00007fc5d072abf0 RDI: 00000000000000f0
RBP: 0000000020000180 R08: 00000000000000f0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00007fc5d072b6d4
R13: 00000000004c64e1 R14: 00000000004db9c0 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea000232ec80 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 dead000000000200 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808cbb2700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88808cbb2780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88808cbb2800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                          ^
 ffff88808cbb2880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88808cbb2900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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