KMSAN: uninit-value in __flow_hash_from_keys (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    088c01ea kmsan: fix comment, NFC
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1556e137200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=68044283f8b8640d
dashboard link: https://syzkaller.appspot.com/bug?extid=3bfc4436d26db9a5ca18
compiler:       clang version 8.0.0 (trunk 350509)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3bfc4436d26db9a5ca18@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KMSAN: uninit-value in __flow_hash_consistentify  
net/core/flow_dissector.c:1318 [inline]
BUG: KMSAN: uninit-value in __flow_hash_from_keys+0x544/0x1070  
net/core/flow_dissector.c:1347
CPU: 0 PID: 14493 Comm: syz-executor.2 Not tainted 5.1.0-rc2+ #21
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+0x173/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x131/0x2a0 mm/kmsan/kmsan.c:624
 __msan_warning+0x7a/0xf0 mm/kmsan/kmsan_instr.c:310
 __flow_hash_consistentify net/core/flow_dissector.c:1318 [inline]
 __flow_hash_from_keys+0x544/0x1070 net/core/flow_dissector.c:1347
 ___skb_get_hash net/core/flow_dissector.c:1370 [inline]
 __skb_get_hash+0x16d/0x3e0 net/core/flow_dissector.c:1433
 skb_get_hash include/linux/skbuff.h:1326 [inline]
 ip_tunnel_xmit+0x99c/0x3310 net/ipv4/ip_tunnel.c:750
 __gre_xmit net/ipv4/ip_gre.c:444 [inline]
 gre_tap_xmit+0xaa5/0xbb0 net/ipv4/ip_gre.c:707
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 sch_direct_xmit+0x58a/0x880 net/sched/sch_generic.c:327
 qdisc_restart net/sched/sch_generic.c:390 [inline]
 __qdisc_run+0x1cd7/0x34b0 net/sched/sch_generic.c:398
 qdisc_run include/net/pkt_sched.h:121 [inline]
 __dev_xmit_skb net/core/dev.c:3473 [inline]
 __dev_queue_xmit+0x1e51/0x3ce0 net/core/dev.c:3832
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 br_dev_queue_push_xmit+0x803/0x8b0 net/bridge/br_forward.c:56
 NF_HOOK include/linux/netfilter.h:289 [inline]
 br_forward_finish net/bridge/br_forward.c:69 [inline]
 NF_HOOK include/linux/netfilter.h:289 [inline]
 __br_forward+0xa58/0xe10 net/bridge/br_forward.c:113
 deliver_clone net/bridge/br_forward.c:129 [inline]
 maybe_deliver net/bridge/br_forward.c:184 [inline]
 br_flood+0xc65/0x10b0 net/bridge/br_forward.c:226
 br_dev_xmit+0x1610/0x16a0 net/bridge/br_device.c:99
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 neigh_resolve_output+0xab7/0xb40 net/core/neighbour.c:1487
 neigh_output include/net/neighbour.h:508 [inline]
 ip_finish_output2+0x1709/0x1930 net/ipv4/ip_output.c:229
 ip_finish_output+0xd2b/0xfd0 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:278 [inline]
 ip_output+0x53f/0x610 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:444 [inline]
 ip_local_out+0x164/0x1d0 net/ipv4/ip_output.c:124
 iptunnel_xmit+0x8a7/0xde0 net/ipv4/ip_tunnel_core.c:91
 ip_tunnel_xmit+0x2f46/0x3310 net/ipv4/ip_tunnel.c:831
 __gre_xmit net/ipv4/ip_gre.c:444 [inline]
 ipgre_xmit+0x1098/0x11c0 net/ipv4/ip_gre.c:628
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 packet_snd net/packet/af_packet.c:2931 [inline]
 packet_sendmsg+0x80f5/0x8ff0 net/packet/af_packet.c:2956
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg net/socket.c:632 [inline]
 ___sys_sendmsg+0xdb3/0x1220 net/socket.c:2137
 __sys_sendmsg net/socket.c:2175 [inline]
 __do_sys_sendmsg net/socket.c:2184 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2182
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2182
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x458209
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007febe94fac78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458209
RDX: 0000000000000000 RSI: 0000000020000200 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007febe94fb6d4
R13: 00000000004c581a R14: 00000000004d9ad8 R15: 00000000ffffffff

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:205 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:220 [inline]
 kmsan_internal_chain_origin+0x134/0x230 mm/kmsan/kmsan.c:426
 kmsan_memcpy_memmove_metadata+0xb5b/0xfe0 mm/kmsan/kmsan.c:304
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:324
 __msan_memcpy+0x58/0x70 mm/kmsan/kmsan_instr.c:139
 __skb_flow_dissect+0x3303/0x7570 net/core/flow_dissector.c:856
 skb_flow_dissect_flow_keys include/linux/skbuff.h:1303 [inline]
 ___skb_get_hash net/core/flow_dissector.c:1367 [inline]
 __skb_get_hash+0x142/0x3e0 net/core/flow_dissector.c:1433
 skb_get_hash include/linux/skbuff.h:1326 [inline]
 ip_tunnel_xmit+0x99c/0x3310 net/ipv4/ip_tunnel.c:750
 __gre_xmit net/ipv4/ip_gre.c:444 [inline]
 gre_tap_xmit+0xaa5/0xbb0 net/ipv4/ip_gre.c:707
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 sch_direct_xmit+0x58a/0x880 net/sched/sch_generic.c:327
 qdisc_restart net/sched/sch_generic.c:390 [inline]
 __qdisc_run+0x1cd7/0x34b0 net/sched/sch_generic.c:398
 qdisc_run include/net/pkt_sched.h:121 [inline]
 __dev_xmit_skb net/core/dev.c:3473 [inline]
 __dev_queue_xmit+0x1e51/0x3ce0 net/core/dev.c:3832
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 br_dev_queue_push_xmit+0x803/0x8b0 net/bridge/br_forward.c:56
 NF_HOOK include/linux/netfilter.h:289 [inline]
 br_forward_finish net/bridge/br_forward.c:69 [inline]
 NF_HOOK include/linux/netfilter.h:289 [inline]
 __br_forward+0xa58/0xe10 net/bridge/br_forward.c:113
 deliver_clone net/bridge/br_forward.c:129 [inline]
 maybe_deliver net/bridge/br_forward.c:184 [inline]
 br_flood+0xc65/0x10b0 net/bridge/br_forward.c:226
 br_dev_xmit+0x1610/0x16a0 net/bridge/br_device.c:99
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 neigh_resolve_output+0xab7/0xb40 net/core/neighbour.c:1487
 neigh_output include/net/neighbour.h:508 [inline]
 ip_finish_output2+0x1709/0x1930 net/ipv4/ip_output.c:229
 ip_finish_output+0xd2b/0xfd0 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:278 [inline]
 ip_output+0x53f/0x610 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:444 [inline]
 ip_local_out+0x164/0x1d0 net/ipv4/ip_output.c:124
 iptunnel_xmit+0x8a7/0xde0 net/ipv4/ip_tunnel_core.c:91
 ip_tunnel_xmit+0x2f46/0x3310 net/ipv4/ip_tunnel.c:831
 __gre_xmit net/ipv4/ip_gre.c:444 [inline]
 ipgre_xmit+0x1098/0x11c0 net/ipv4/ip_gre.c:628
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 packet_snd net/packet/af_packet.c:2931 [inline]
 packet_sendmsg+0x80f5/0x8ff0 net/packet/af_packet.c:2956
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg net/socket.c:632 [inline]
 ___sys_sendmsg+0xdb3/0x1220 net/socket.c:2137
 __sys_sendmsg net/socket.c:2175 [inline]
 __do_sys_sendmsg net/socket.c:2184 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2182
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2182
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:205 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:220 [inline]
 kmsan_internal_chain_origin+0x134/0x230 mm/kmsan/kmsan.c:426
 kmsan_memcpy_memmove_metadata+0xb5b/0xfe0 mm/kmsan/kmsan.c:304
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:324
 __msan_memcpy+0x58/0x70 mm/kmsan/kmsan_instr.c:139
 pskb_expand_head+0x3aa/0x1a30 net/core/skbuff.c:1478
 __skb_cow include/linux/skbuff.h:3029 [inline]
 skb_cow_head include/linux/skbuff.h:3063 [inline]
 gre_tap_xmit+0x7dd/0xbb0 net/ipv4/ip_gre.c:704
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 sch_direct_xmit+0x58a/0x880 net/sched/sch_generic.c:327
 qdisc_restart net/sched/sch_generic.c:390 [inline]
 __qdisc_run+0x1cd7/0x34b0 net/sched/sch_generic.c:398
 qdisc_run include/net/pkt_sched.h:121 [inline]
 __dev_xmit_skb net/core/dev.c:3473 [inline]
 __dev_queue_xmit+0x1e51/0x3ce0 net/core/dev.c:3832
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 br_dev_queue_push_xmit+0x803/0x8b0 net/bridge/br_forward.c:56
 NF_HOOK include/linux/netfilter.h:289 [inline]
 br_forward_finish net/bridge/br_forward.c:69 [inline]
 NF_HOOK include/linux/netfilter.h:289 [inline]
 __br_forward+0xa58/0xe10 net/bridge/br_forward.c:113
 deliver_clone net/bridge/br_forward.c:129 [inline]
 maybe_deliver net/bridge/br_forward.c:184 [inline]
 br_flood+0xc65/0x10b0 net/bridge/br_forward.c:226
 br_dev_xmit+0x1610/0x16a0 net/bridge/br_device.c:99
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 neigh_resolve_output+0xab7/0xb40 net/core/neighbour.c:1487
 neigh_output include/net/neighbour.h:508 [inline]
 ip_finish_output2+0x1709/0x1930 net/ipv4/ip_output.c:229
 ip_finish_output+0xd2b/0xfd0 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:278 [inline]
 ip_output+0x53f/0x610 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:444 [inline]
 ip_local_out+0x164/0x1d0 net/ipv4/ip_output.c:124
 iptunnel_xmit+0x8a7/0xde0 net/ipv4/ip_tunnel_core.c:91
 ip_tunnel_xmit+0x2f46/0x3310 net/ipv4/ip_tunnel.c:831
 __gre_xmit net/ipv4/ip_gre.c:444 [inline]
 ipgre_xmit+0x1098/0x11c0 net/ipv4/ip_gre.c:628
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 packet_snd net/packet/af_packet.c:2931 [inline]
 packet_sendmsg+0x80f5/0x8ff0 net/packet/af_packet.c:2956
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg net/socket.c:632 [inline]
 ___sys_sendmsg+0xdb3/0x1220 net/socket.c:2137
 __sys_sendmsg net/socket.c:2175 [inline]
 __do_sys_sendmsg net/socket.c:2184 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2182
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2182
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:205 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:220 [inline]
 kmsan_internal_chain_origin+0x134/0x230 mm/kmsan/kmsan.c:426
 kmsan_memcpy_memmove_metadata+0xb5b/0xfe0 mm/kmsan/kmsan.c:304
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:324
 __msan_memcpy+0x58/0x70 mm/kmsan/kmsan_instr.c:139
 pskb_expand_head+0x3aa/0x1a30 net/core/skbuff.c:1478
 __skb_cow include/linux/skbuff.h:3029 [inline]
 skb_cow_head include/linux/skbuff.h:3063 [inline]
 ip_tunnel_xmit+0x2c4e/0x3310 net/ipv4/ip_tunnel.c:824
 __gre_xmit net/ipv4/ip_gre.c:444 [inline]
 ipgre_xmit+0x1098/0x11c0 net/ipv4/ip_gre.c:628
 __netdev_start_xmit include/linux/netdevice.h:4411 [inline]
 netdev_start_xmit include/linux/netdevice.h:4420 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e9f/0x3ce0 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 packet_snd net/packet/af_packet.c:2931 [inline]
 packet_sendmsg+0x80f5/0x8ff0 net/packet/af_packet.c:2956
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg net/socket.c:632 [inline]
 ___sys_sendmsg+0xdb3/0x1220 net/socket.c:2137
 __sys_sendmsg net/socket.c:2175 [inline]
 __do_sys_sendmsg net/socket.c:2184 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2182
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2182
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:205 [inline]
 kmsan_internal_poison_shadow+0x92/0x150 mm/kmsan/kmsan.c:159
 kmsan_kmalloc+0xa9/0x130 mm/kmsan/kmsan_hooks.c:173
 kmsan_slab_alloc+0xe/0x10 mm/kmsan/kmsan_hooks.c:182
 slab_post_alloc_hook mm/slab.h:441 [inline]
 slab_alloc_node mm/slub.c:2771 [inline]
 __kmalloc_node_track_caller+0xead/0x1000 mm/slub.c:4396
 __kmalloc_reserve net/core/skbuff.c:140 [inline]
 __alloc_skb+0x309/0xa20 net/core/skbuff.c:208
 alloc_skb include/linux/skbuff.h:1059 [inline]
 alloc_skb_with_frags+0x186/0xa60 net/core/skbuff.c:5287
 sock_alloc_send_pskb+0xafd/0x10a0 net/core/sock.c:2220
 packet_alloc_skb net/packet/af_packet.c:2781 [inline]
 packet_snd net/packet/af_packet.c:2874 [inline]
 packet_sendmsg+0x6349/0x8ff0 net/packet/af_packet.c:2956
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg net/socket.c:632 [inline]
 ___sys_sendmsg+0xdb3/0x1220 net/socket.c:2137
 __sys_sendmsg net/socket.c:2175 [inline]
 __do_sys_sendmsg net/socket.c:2184 [inline]
 __se_sys_sendmsg+0x305/0x460 net/socket.c:2182
 __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2182
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================


---
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