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BUG: KMSAN: uninit-value in ip6_parse_tlv+0x8b8/0xcb0 net/ipv6/exthdrs.c:169
CPU: 1 PID: 22115 Comm: syz-executor.5 Not tainted 5.7.0-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:77 [inline]
 dump_stack+0x1c9/0x220 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 ip6_parse_tlv+0x8b8/0xcb0 net/ipv6/exthdrs.c:169
 ipv6_parse_hopopts+0x493/0x7c0 net/ipv6/exthdrs.c:1043
 ip6_rcv_core+0x1b08/0x1ff0 net/ipv6/ip6_input.c:278
 ipv6_rcv+0xe3/0x710 net/ipv6/ip6_input.c:304
 __netif_receive_skb_one_core net/core/dev.c:5188 [inline]
 __netif_receive_skb net/core/dev.c:5302 [inline]
 netif_receive_skb_internal net/core/dev.c:5392 [inline]
 netif_receive_skb+0x66b/0xf20 net/core/dev.c:5451
 tun_rx_batched drivers/net/tun.c:1516 [inline]
 tun_get_user+0x6d60/0x71e0 drivers/net/tun.c:1963
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:1992
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0xa5a/0xca0 fs/read_write.c:497
 vfs_write+0x444/0x8e0 fs/read_write.c:559
 ksys_write+0x267/0x450 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:621
 __x64_sys_write+0x4a/0x70 fs/read_write.c:621
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cba9
Code: 8d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f26bcf38c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000050ffc0 RCX: 000000000045cba9
RDX: 000000000000fdef RSI: 0000000020000180 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000d8b R14: 00000000004cfe0f R15: 00007f26bcf396d4

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
 kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:80
 slab_alloc_node mm/slub.c:2802 [inline]
 __kmalloc_node_track_caller+0xb40/0x1200 mm/slub.c:4436
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x2fd/0xac0 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1083 [inline]
 alloc_skb_with_frags+0x18c/0xa70 net/core/skbuff.c:5772
 sock_alloc_send_pskb+0xada/0xc60 net/core/sock.c:2265
 tun_alloc_skb drivers/net/tun.c:1492 [inline]
 tun_get_user+0x1260/0x71e0 drivers/net/tun.c:1808
 tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:1992
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0xa5a/0xca0 fs/read_write.c:497
 vfs_write+0x444/0x8e0 fs/read_write.c:559
 ksys_write+0x267/0x450 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:621
 __x64_sys_write+0x4a/0x70 fs/read_write.c:621
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
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