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BUG: KASAN: null-ptr-deref in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: null-ptr-deref in atomic_fetch_add_unless include/linux/atomic-fallback.h:1086 [inline]
BUG: KASAN: null-ptr-deref in atomic_add_unless include/linux/atomic-fallback.h:1111 [inline]
BUG: KASAN: null-ptr-deref in atomic_inc_not_zero include/linux/atomic-fallback.h:1127 [inline]
BUG: KASAN: null-ptr-deref in dst_hold_safe include/net/dst.h:297 [inline]
BUG: KASAN: null-ptr-deref in ip6_hold_safe+0xad/0x380 net/ipv6/route.c:1050
Read of size 4 at addr 00000000000000b9 by task syz-executor.3/31715

CPU: 1 PID: 31715 Comm: syz-executor.3 Not tainted 5.2.0-rc1+ #1
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
 __kasan_report.cold+0x5/0x40 mm/kasan/report.c:321
 kasan_report+0x12/0x20 mm/kasan/common.c:614
 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:94
 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
 atomic_fetch_add_unless include/linux/atomic-fallback.h:1086 [inline]
 atomic_add_unless include/linux/atomic-fallback.h:1111 [inline]
 atomic_inc_not_zero include/linux/atomic-fallback.h:1127 [inline]
 dst_hold_safe include/net/dst.h:297 [inline]
 ip6_hold_safe+0xad/0x380 net/ipv6/route.c:1050
 rt6_get_pcpu_route net/ipv6/route.c:1277 [inline]
 ip6_pol_route+0x336/0x1050 net/ipv6/route.c:2028
 ip6_pol_route_input+0x65/0x80 net/ipv6/route.c:2047
 fib6_rule_lookup+0x133/0x5a0 net/ipv6/fib6_rules.c:116
 ip6_route_input_lookup+0xb7/0xd0 net/ipv6/route.c:2059
 ip6_route_input+0x5e2/0x9e0 net/ipv6/route.c:2194
 ip6_rcv_finish_core.isra.0+0x174/0x590 net/ipv6/ip6_input.c:67
 ip6_rcv_finish+0x17a/0x310 net/ipv6/ip6_input.c:78
 NF_HOOK include/linux/netfilter.h:305 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ipv6_rcv+0x10e/0x420 net/ipv6/ip6_input.c:276
 __netif_receive_skb_one_core+0x113/0x1a0 net/core/dev.c:4990
 __netif_receive_skb+0x2c/0x1d0 net/core/dev.c:5104
 netif_receive_skb_internal+0x117/0x5c0 net/core/dev.c:5207
 napi_frags_finish net/core/dev.c:5774 [inline]
 napi_gro_frags+0xada/0xd10 net/core/dev.c:5848
 tun_get_user+0x2f3c/0x3ff0 drivers/net/tun.c:1991
 tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2037
 call_write_iter include/linux/fs.h:1872 [inline]
 do_iter_readv_writev+0x5f8/0x8f0 fs/read_write.c:693
 do_iter_write fs/read_write.c:970 [inline]
 do_iter_write+0x184/0x610 fs/read_write.c:951
 vfs_writev+0x1b3/0x2f0 fs/read_write.c:1015
 do_writev+0x15b/0x330 fs/read_write.c:1058
 __do_sys_writev fs/read_write.c:1131 [inline]
 __se_sys_writev fs/read_write.c:1128 [inline]
 __x64_sys_writev+0x75/0xb0 fs/read_write.c:1128
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459131
Code: 75 14 b8 14 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 b9 fb ff c3 48 83 ec 08 e8 fa 2c 00 00 48 89 04 24 b8 14 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 43 2d 00 00 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007f405fa24ba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0000000000000160 RCX: 0000000000459131
RDX: 0000000000000001 RSI: 00007f405fa24c00 RDI: 00000000000000f0
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000293 R12: 00007f405fa256d4
R13: 00000000004c7d21 R14: 00000000004de160 R15: 00000000ffffffff
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