Subject: KMSAN: uninit-value in ip_check_mc_rcu (3)

From: syzbot <[email-masked]>
Date: Sat, 12 Sep 2020 00:59:19 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    3b3ea602 x86: add failure injection to get/put/clear_user
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1357bd3e900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3afe005fb99591f
dashboard link: https://syzkaller.appspot.com/bug?extid=64be9532cb0d88808aad
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

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]

=====================================================
BUG: KMSAN: uninit-value in ip_check_mc_rcu+0x340/0x840 net/ipv4/igmp.c:2707
CPU: 0 PID: 8708 Comm: syz-executor.0 Not tainted 5.8.0-rc5-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+0x21c/0x280 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
 ip_check_mc_rcu+0x340/0x840 net/ipv4/igmp.c:2707
 __mkroute_output+0x6a6/0x2860 net/ipv4/route.c:2388
 ip_route_output_key_hash_rcu+0x1eb4/0x2000 net/ipv4/route.c:2669
 ip_route_output_key_hash net/ipv4/route.c:2495 [inline]
 __ip_route_output_key include/net/route.h:126 [inline]
 ip_route_output_flow+0x211/0x420 net/ipv4/route.c:2758
 ip_route_output_key include/net/route.h:142 [inline]
 ip_tunnel_xmit+0x1772/0x3aa0 net/ipv4/ip_tunnel.c:751
 __gre_xmit net/ipv4/ip_gre.c:466 [inline]
 ipgre_xmit+0x12a2/0x13c0 net/ipv4/ip_gre.c:650
 __netdev_start_xmit include/linux/netdevice.h:4611 [inline]
 netdev_start_xmit include/linux/netdevice.h:4625 [inline]
 xmit_one+0x3cf/0x750 net/core/dev.c:3556
 dev_hard_start_xmit net/core/dev.c:3572 [inline]
 __dev_queue_xmit+0x3aad/0x4470 net/core/dev.c:4131
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:4164
 packet_snd net/packet/af_packet.c:2979 [inline]
 packet_sendmsg+0x8542/0x9a80 net/packet/af_packet.c:3004
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xc82/0x1240 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmsg+0x6d1/0x840 net/socket.c:2439
 __do_sys_sendmsg net/socket.c:2448 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2446
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2446
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d5b9
Code: Bad RIP value.
RSP: 002b:00007f2932958c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000002ccc0 RCX: 000000000045d5b9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000005
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 000000000169fb6f R14: 00007f29329599c0 R15: 000000000118cf4c

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310
 __msan_chain_origin+0x50/0x90 mm/kmsan/kmsan_instr.c:165
 ip_tunnel_init_flow include/net/ip_tunnels.h:248 [inline]
 ip_tunnel_xmit+0xe3d/0x3aa0 net/ipv4/ip_tunnel.c:733
 __gre_xmit net/ipv4/ip_gre.c:466 [inline]
 ipgre_xmit+0x12a2/0x13c0 net/ipv4/ip_gre.c:650
 __netdev_start_xmit include/linux/netdevice.h:4611 [inline]
 netdev_start_xmit include/linux/netdevice.h:4625 [inline]
 xmit_one+0x3cf/0x750 net/core/dev.c:3556
 dev_hard_start_xmit net/core/dev.c:3572 [inline]
 __dev_queue_xmit+0x3aad/0x4470 net/core/dev.c:4131
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:4164
 packet_snd net/packet/af_packet.c:2979 [inline]
 packet_sendmsg+0x8542/0x9a80 net/packet/af_packet.c:3004
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xc82/0x1240 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmsg+0x6d1/0x840 net/socket.c:2439
 __do_sys_sendmsg net/socket.c:2448 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2446
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2446
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310
 kmsan_memcpy_memmove_metadata+0x272/0x2e0 mm/kmsan/kmsan.c:247
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:267
 __msan_memcpy+0x43/0x50 mm/kmsan/kmsan_instr.c:116
 pskb_expand_head+0x3fd/0x1e30 net/core/skbuff.c:1636
 __skb_cow include/linux/skbuff.h:3145 [inline]
 skb_cow_head include/linux/skbuff.h:3179 [inline]
 ipgre_xmit+0x88c/0x13c0 net/ipv4/ip_gre.c:629
 __netdev_start_xmit include/linux/netdevice.h:4611 [inline]
 netdev_start_xmit include/linux/netdevice.h:4625 [inline]
 xmit_one+0x3cf/0x750 net/core/dev.c:3556
 dev_hard_start_xmit net/core/dev.c:3572 [inline]
 __dev_queue_xmit+0x3aad/0x4470 net/core/dev.c:4131
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:4164
 packet_snd net/packet/af_packet.c:2979 [inline]
 packet_sendmsg+0x8542/0x9a80 net/packet/af_packet.c:3004
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xc82/0x1240 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmsg+0x6d1/0x840 net/socket.c:2439
 __do_sys_sendmsg net/socket.c:2448 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2446
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2446
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

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:2839 [inline]
 __kmalloc_node_track_caller+0xeab/0x12e0 mm/slub.c:4478
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x35f/0xb30 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1083 [inline]
 alloc_skb_with_frags+0x1f2/0xc10 net/core/skbuff.c:5770
 sock_alloc_send_pskb+0xc83/0xe50 net/core/sock.c:2356
 packet_alloc_skb net/packet/af_packet.c:2827 [inline]
 packet_snd net/packet/af_packet.c:2922 [inline]
 packet_sendmsg+0x6abb/0x9a80 net/packet/af_packet.c:3004
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0xc82/0x1240 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmsg+0x6d1/0x840 net/socket.c:2439
 __do_sys_sendmsg net/socket.c:2448 [inline]
 __se_sys_sendmsg+0x97/0xb0 net/socket.c:2446
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2446
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================

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