KMSAN: uninit-value in ipv6_find_tlv

From: syzbot
Date: Tue Aug 13 2019 - 10:48:08 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 61ccdad1 Revert "drm/bochs: Use shadow buffer for bochs fr..
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1229a18c600000
kernel config: https://syzkaller.appspot.com/x/.config?x=27abc558ecb16a3b
dashboard link: https://syzkaller.appspot.com/bug?extid=8257f4dcef79de670baf
compiler: clang version 9.0.0 (/home/glider/llvm/clang 80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12480dce600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1659dc4a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8257f4dcef79de670baf@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KMSAN: uninit-value in ipv6_find_tlv+0x370/0x3c0 net/ipv6/exthdrs_core.c:147
CPU: 1 PID: 12844 Comm: syz-executor755 Not tainted 5.3.0-rc3+ #17
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: 0033:0x452be9
Code: e8 7c e6 ff ff 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 1b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fbf62544ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006efa08 RCX: 0000000000452be9
RDX: 00000000000041a0 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00000000006efa00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006efa0c
R13: 00007ffec68fe78f R14: 00007fbf625459c0 R15: 20c49ba5e353f7cf

Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:187 [inline]
kmsan_internal_poison_shadow+0x53/0xa0 mm/kmsan/kmsan.c:146
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
==================================================================

---
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Next message: Paul E. McKenney: "Re: [PATCH RFC tip/core/rcu 14/14] rcu/nohz: Make multi_cpu_stop() enable tick on all online CPUs"
Previous message: David Gibson: "Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted"
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