KMSAN: uninit-value in ipv6_find

KMSAN: uninit-value in ipv6_find_tlv
Status: upstream: reported C repro on 2019/08/13 14:48
Reported-by: syzbot+8257f4dcef79de670baf@syzkaller.appspotmail.com
First crash: 614d, last: 418d

Sample crash report:

==================================================================
BUG: KMSAN: uninit-value in ipv6_find_tlv+0x370/0x3c0 net/ipv6/exthdrs_core.c:147
CPU: 0 PID: 12718 Comm: syz-executor830 Not tainted 5.3.0-rc7+ #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+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
 __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
 ipv6_find_tlv+0x370/0x3c0 net/ipv6/exthdrs_core.c:147
 ip6_find_1stfragopt+0x2b6/0x500 net/ipv6/output_core.c:102
 ip6_fragment+0x275/0x37d0 net/ipv6/ip6_output.c:775
 __ip6_finish_output+0x753/0x8f0 net/ipv6/ip6_output.c:140
 ip6_finish_output+0x2db/0x420 net/ipv6/ip6_output.c:152
 NF_HOOK_COND include/linux/netfilter.h:294 [inline]
 ip6_output+0x5d3/0x720 net/ipv6/ip6_output.c:175
 dst_output include/net/dst.h:436 [inline]
 ip6_local_out+0x164/0x1d0 net/ipv6/output_core.c:179
 ip6_send_skb net/ipv6/ip6_output.c:1791 [inline]
 ip6_push_pending_frames+0x215/0x4f0 net/ipv6/ip6_output.c:1811
 rawv6_push_pending_frames net/ipv6/raw.c:613 [inline]
 rawv6_sendmsg+0x40da/0x5b10 net/ipv6/raw.c:954
 inet_sendmsg+0x2d8/0x2e0 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg net/socket.c:657 [inline]
 sock_write_iter+0x599/0x650 net/socket.c:989
 call_write_iter include/linux/fs.h:1870 [inline]
 new_sync_write fs/read_write.c:483 [inline]
 __vfs_write+0xa2c/0xcb0 fs/read_write.c:496
 vfs_write+0x481/0x920 fs/read_write.c:558
 ksys_write+0x265/0x430 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:620
 __x64_sys_write+0x4a/0x70 fs/read_write.c:620
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x448a59
Code: e8 5c 14 03 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 ab 0e fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fce7f5f6d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dec28 RCX: 0000000000448a59
RDX: 00000000000041a0 RSI: 00000000200001c0 RDI: 0000000000000004
RBP: 00000000006dec20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dec2c
R13: 0000000000000000 R14: 0000000000000000 R15: 00007265746c6966

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:189 [inline]
 kmsan_internal_poison_shadow+0x58/0xb0 mm/kmsan/kmsan.c:148
 kmsan_slab_alloc+0xaa/0x120 mm/kmsan/kmsan_hooks.c:175
 slab_alloc_node mm/slub.c:2790 [inline]
 __kmalloc_node_track_caller+0xb55/0x1320 mm/slub.c:4388
 __kmalloc_reserve net/core/skbuff.c:141 [inline]
 __alloc_skb+0x306/0xa10 net/core/skbuff.c:209
 alloc_skb include/linux/skbuff.h:1056 [inline]
 __ip6_append_data+0x46ad/0x6060 net/ipv6/ip6_output.c:1514
 ip6_append_data+0x3c2/0x650 net/ipv6/ip6_output.c:1683
 rawv6_sendmsg+0x232e/0x5b10 net/ipv6/raw.c:947
 inet_sendmsg+0x2d8/0x2e0 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg net/socket.c:657 [inline]
 sock_write_iter+0x599/0x650 net/socket.c:989
 call_write_iter include/linux/fs.h:1870 [inline]
 new_sync_write fs/read_write.c:483 [inline]
 __vfs_write+0xa2c/0xcb0 fs/read_write.c:496
 vfs_write+0x481/0x920 fs/read_write.c:558
 ksys_write+0x265/0x430 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:620
 __x64_sys_write+0x4a/0x70 fs/read_write.c:620
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================

Crashes (12):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-kmsan-gce	2019/09/11 01:12	https://github.com/google/kmsan.git master	014077b5	a60cb4cd	.config	log	report	syz	C
ci-upstream-kmsan-gce	2019/08/09 13:58	https://github.com/google/kmsan.git master	61ccdad1	ede31a9b	.config	log	report	syz	C
ci-upstream-kmsan-gce	2020/02/22 04:33	https://github.com/google/kmsan.git master	8bbbc5cf	2ffa6679	.config	log	report
ci-upstream-kmsan-gce	2020/01/29 07:56	https://github.com/google/kmsan.git master	686a4f77	c8e81ce4	.config	log	report
ci-upstream-kmsan-gce	2020/01/29 07:23	https://github.com/google/kmsan.git master	686a4f77	c8e81ce4	.config	log	report
ci-upstream-kmsan-gce	2019/12/07 15:30	https://github.com/google/kmsan.git master	f8f75f03	85f26751	.config	log	report
ci-upstream-kmsan-gce	2019/12/01 11:04	https://github.com/google/kmsan.git master	e2027b2c	a76bf83f	.config	log	report
ci-upstream-kmsan-gce	2019/11/27 20:38	https://github.com/google/kmsan.git master	c543ab66	0d63f89c	.config	log	report
ci-upstream-kmsan-gce	2019/11/10 22:09	https://github.com/google/kmsan.git master	e741088f	dc438b91	.config	log	report
ci-upstream-kmsan-gce	2019/11/01 05:48	https://github.com/google/kmsan.git master	6f88939b	a41ca8fa	.config	log	report
ci-upstream-kmsan-gce	2019/10/20 09:40	https://github.com/google/kmsan.git master	3c8ca708	8c88c9c1	.config	log	report
ci-upstream-kmsan-gce	2019/08/09 13:04	https://github.com/google/kmsan.git master	61ccdad1	ede31a9b	.config	log	report