KMSAN: uninit-value in __skb_flow_dissect (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: fa169025 kmsan: get rid of unused static functions in kmsa..
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1498dde7600000
kernel config: https://syzkaller.appspot.com/x/.config?x=49548798e87d32d7
dashboard link: https://syzkaller.appspot.com/bug?extid=591798c238c7b7108f72
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)

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+591798...@syzkaller.appspotmail.com

device nr0 entered promiscuous mode
=====================================================
BUG: KMSAN: uninit-value in __skb_flow_dissect+0x207e/0x7a40
net/core/flow_dissector.c:957
CPU: 1 PID: 21243 Comm: syz-executor.1 Not tainted 5.4.0-rc2+ #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+0x14e/0x2c0 mm/kmsan/kmsan_report.c:110
__msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:245
__skb_flow_dissect+0x207e/0x7a40 net/core/flow_dissector.c:957
__skb_get_hash_symmetric+0x108/0x260 net/core/flow_dissector.c:1523
fanout_demux_hash net/packet/af_packet.c:1314 [inline]
packet_rcv_fanout+0xa73/0x2550 net/packet/af_packet.c:1429
deliver_skb net/core/dev.c:1969 [inline]
__netif_receive_skb_core+0x1cab/0x51a0 net/core/dev.c:4896
__netif_receive_skb_one_core net/core/dev.c:5008 [inline]
__netif_receive_skb net/core/dev.c:5124 [inline]
netif_receive_skb_internal+0x3cc/0xc20 net/core/dev.c:5214
netif_receive_skb+0x1da/0x3a0 net/core/dev.c:5273
tun_rx_batched drivers/net/tun.c:1553 [inline]
tun_get_user+0x6c44/0x6f70 drivers/net/tun.c:1993
tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2022
call_write_iter include/linux/fs.h:1895 [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+0xb6/0x160 arch/x86/entry/common.c:291
entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x459a59
Code: fd b7 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f073d62ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a59
RDX: 000000000000b107 RSI: 00000000200000c0 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f073d62b6d4
R13: 00000000004c9ea0 R14: 00000000004e1ac0 R15: 00000000ffffffff

Uninit was stored to memory at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:154 [inline]
kmsan_internal_chain_origin+0xbd/0x170 mm/kmsan/kmsan.c:321
__msan_chain_origin+0x6b/0xe0 mm/kmsan/kmsan_instr.c:179
__skb_flow_dissect+0x30ee/0x7a40 net/core/flow_dissector.c:1060
__skb_get_hash_symmetric+0x108/0x260 net/core/flow_dissector.c:1523
fanout_demux_hash net/packet/af_packet.c:1314 [inline]
packet_rcv_fanout+0xa73/0x2550 net/packet/af_packet.c:1429
deliver_skb net/core/dev.c:1969 [inline]
__netif_receive_skb_core+0x1cab/0x51a0 net/core/dev.c:4896
__netif_receive_skb_one_core net/core/dev.c:5008 [inline]
__netif_receive_skb net/core/dev.c:5124 [inline]
netif_receive_skb_internal+0x3cc/0xc20 net/core/dev.c:5214
netif_receive_skb+0x1da/0x3a0 net/core/dev.c:5273
tun_rx_batched drivers/net/tun.c:1553 [inline]
tun_get_user+0x6c44/0x6f70 drivers/net/tun.c:1993
tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2022
call_write_iter include/linux/fs.h:1895 [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+0xb6/0x160 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:154 [inline]
kmsan_internal_chain_origin+0xbd/0x170 mm/kmsan/kmsan.c:321
__msan_chain_origin+0x6b/0xe0 mm/kmsan/kmsan_instr.c:179
vlan_set_encap_proto include/linux/skbuff.h:1587 [inline]
skb_vlan_untag+0x6bc/0xd20 net/core/skbuff.c:5329
__netif_receive_skb_core+0x833/0x51a0 net/core/dev.c:4855
__netif_receive_skb_one_core net/core/dev.c:5008 [inline]
__netif_receive_skb net/core/dev.c:5124 [inline]
netif_receive_skb_internal+0x3cc/0xc20 net/core/dev.c:5214
netif_receive_skb+0x1da/0x3a0 net/core/dev.c:5273
tun_rx_batched drivers/net/tun.c:1553 [inline]
tun_get_user+0x6c44/0x6f70 drivers/net/tun.c:1993
tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2022
call_write_iter include/linux/fs.h:1895 [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+0xb6/0x160 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:154 [inline]
kmsan_internal_poison_shadow+0x60/0x120 mm/kmsan/kmsan.c:137
kmsan_slab_alloc+0xaa/0x120 mm/kmsan/kmsan_hooks.c:103
slab_alloc_node mm/slub.c:2792 [inline]
__kmalloc_node_track_caller+0xb55/0x1320 mm/slub.c:4390
__kmalloc_reserve net/core/skbuff.c:141 [inline]
__alloc_skb+0x306/0xa10 net/core/skbuff.c:209
alloc_skb include/linux/skbuff.h:1050 [inline]
alloc_skb_with_frags+0x18c/0xa80 net/core/skbuff.c:5659
sock_alloc_send_pskb+0xafd/0x10a0 net/core/sock.c:2240
tun_alloc_skb drivers/net/tun.c:1529 [inline]
tun_get_user+0x1132/0x6f70 drivers/net/tun.c:1843
tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2022
call_write_iter include/linux/fs.h:1895 [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+0xb6/0x160 arch/x86/entry/common.c:291
entry_SYSCALL_64_after_hwframe+0x63/0xe7
=====================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.