Subject: [syzbot] KMSAN: uninit-value in iptable_mangle_hook (5)

From: syzbot <[email-masked]>
Date: Tue, 16 Mar 2021 22:49:18 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    29ad81a1 arch/x86: add missing include to sparsemem.h
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=179b38f6d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8b976581f6bd1e7d
dashboard link: https://syzkaller.appspot.com/bug?extid=9b5e12c49c015d4c1aeb
compiler:       Debian clang version 11.0.1-2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

netlink: 24 bytes leftover after parsing attributes in process `syz-executor.4'.
=====================================================
BUG: KMSAN: uninit-value in ipt_mangle_out net/ipv4/netfilter/iptable_mangle.c:61 [inline]
BUG: KMSAN: uninit-value in iptable_mangle_hook+0x75a/0x8c0 net/ipv4/netfilter/iptable_mangle.c:81
CPU: 1 PID: 25792 Comm: syz-executor.4 Not tainted 5.11.0-rc7-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+0x21c/0x280 lib/dump_stack.c:120
 kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118
 __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197
 ipt_mangle_out net/ipv4/netfilter/iptable_mangle.c:61 [inline]
 iptable_mangle_hook+0x75a/0x8c0 net/ipv4/netfilter/iptable_mangle.c:81
 nf_hook_entry_hookfn include/linux/netfilter.h:136 [inline]
 nf_hook_slow+0x17b/0x460 net/netfilter/core.c:589
 nf_hook include/linux/netfilter.h:256 [inline]
 __ip_local_out+0x78c/0x840 net/ipv4/ip_output.c:115
 ip_local_out+0xa1/0x1e0 net/ipv4/ip_output.c:124
 iptunnel_xmit+0x931/0xf20 net/ipv4/ip_tunnel_core.c:82
 udp_tunnel_xmit_skb+0x526/0x640 net/ipv4/udp_tunnel_core.c:190
 geneve_xmit_skb drivers/net/geneve.c:959 [inline]
 geneve_xmit+0x209e/0x3c20 drivers/net/geneve.c:1059
 __netdev_start_xmit include/linux/netdevice.h:4778 [inline]
 netdev_start_xmit include/linux/netdevice.h:4792 [inline]
 xmit_one+0x2b6/0x760 net/core/dev.c:3574
 dev_hard_start_xmit net/core/dev.c:3590 [inline]
 __dev_queue_xmit+0x3426/0x45c0 net/core/dev.c:4151
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:4184
 packet_snd net/packet/af_packet.c:3006 [inline]
 packet_sendmsg+0x8778/0x9a60 net/packet/af_packet.c:3031
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xcfc/0x12f0 net/socket.c:2345
 ___sys_sendmsg net/socket.c:2399 [inline]
 __sys_sendmsg+0x714/0x830 net/socket.c:2432
 __do_sys_sendmsg net/socket.c:2441 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2439
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2439
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x465f69
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:00007fae1692d188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465f69
RDX: 0000000000008844 RSI: 00000000200005c0 RDI: 0000000000000003
RBP: 00000000004bfa8f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 0000000000a9fb1f R14: 00007fae1692d300 R15: 0000000000022000

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:121 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:289
 __msan_chain_origin+0x57/0xa0 mm/kmsan/kmsan_instr.c:147
 iptunnel_xmit+0xbd6/0xf20 net/ipv4/ip_tunnel_core.c:76
 udp_tunnel_xmit_skb+0x526/0x640 net/ipv4/udp_tunnel_core.c:190
 geneve_xmit_skb drivers/net/geneve.c:959 [inline]
 geneve_xmit+0x209e/0x3c20 drivers/net/geneve.c:1059
 __netdev_start_xmit include/linux/netdevice.h:4778 [inline]
 netdev_start_xmit include/linux/netdevice.h:4792 [inline]
 xmit_one+0x2b6/0x760 net/core/dev.c:3574
 dev_hard_start_xmit net/core/dev.c:3590 [inline]
 __dev_queue_xmit+0x3426/0x45c0 net/core/dev.c:4151
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:4184
 packet_snd net/packet/af_packet.c:3006 [inline]
 packet_sendmsg+0x8778/0x9a60 net/packet/af_packet.c:3031
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xcfc/0x12f0 net/socket.c:2345
 ___sys_sendmsg net/socket.c:2399 [inline]
 __sys_sendmsg+0x714/0x830 net/socket.c:2432
 __do_sys_sendmsg net/socket.c:2441 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2439
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2439
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:121 [inline]
 kmsan_internal_poison_shadow+0x5c/0xf0 mm/kmsan/kmsan.c:104
 kmsan_slab_alloc+0x8d/0xe0 mm/kmsan/kmsan_hooks.c:76
 slab_alloc_node mm/slub.c:2907 [inline]
 __kmalloc_node_track_caller+0xa37/0x1430 mm/slub.c:4527
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x2f8/0xb30 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1099 [inline]
 alloc_skb_with_frags+0x1f3/0xc10 net/core/skbuff.c:5894
 sock_alloc_send_pskb+0xdc1/0xf90 net/core/sock.c:2348
 packet_alloc_skb net/packet/af_packet.c:2854 [inline]
 packet_snd net/packet/af_packet.c:2949 [inline]
 packet_sendmsg+0x6aab/0x9a60 net/packet/af_packet.c:3031
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xcfc/0x12f0 net/socket.c:2345
 ___sys_sendmsg net/socket.c:2399 [inline]
 __sys_sendmsg+0x714/0x830 net/socket.c:2432
 __do_sys_sendmsg net/socket.c:2441 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2439
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2439
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================

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