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BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in atomic_dec_return include/asm-generic/atomic-instrumented.h:340 [inline]
BUG: KASAN: null-ptr-deref in dst_release net/core/dst.c:174 [inline]
BUG: KASAN: null-ptr-deref in dst_release+0x26/0xe0 net/core/dst.c:169
Write of size 4 at addr 0000000000000041 by task syz-executor.1/31322

CPU: 0 PID: 31322 Comm: syz-executor.1 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 __kasan_report mm/kasan/report.c:403 [inline]
 kasan_report.cold+0x5f/0xd8 mm/kasan/report.c:416
 check_region_inline mm/kasan/generic.c:180 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:186
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_dec_return include/asm-generic/atomic-instrumented.h:340 [inline]
 dst_release net/core/dst.c:174 [inline]
 dst_release+0x26/0xe0 net/core/dst.c:169
 dst_cache_destroy net/core/dst_cache.c:160 [inline]
 dst_cache_destroy+0xd4/0x1d0 net/core/dst_cache.c:152
 ipip6_dev_free net/ipv6/sit.c:1405 [inline]
 sit_init_net+0x88b/0xa80 net/ipv6/sit.c:1927
 ops_init+0xaf/0x470 net/core/net_namespace.c:140
 setup_net+0x40f/0xa30 net/core/net_namespace.c:333
 copy_net_ns+0x31e/0x760 net/core/net_namespace.c:474
 create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xbd/0x1f0 kernel/nsproxy.c:226
 ksys_unshare+0x445/0x8e0 kernel/fork.c:2998
 __do_sys_unshare kernel/fork.c:3066 [inline]
 __se_sys_unshare kernel/fork.c:3064 [inline]
 __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3064
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x466459
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4cfc636188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffd9f76336f R14: 00007f4cfc636300 R15: 0000000000022000
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