KMSAN: uninit-value in route4_get

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 21c44613 kmsan: page_alloc: more assuring comment
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=111271e4100000
kernel config: https://syzkaller.appspot.com/x/.config?x=a5915107b3106aaa
dashboard link: https://syzkaller.appspot.com/bug?extid=0f695e9c22e33a40e8b5
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
userspace arch: i386

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+0f695e...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in route4_get+0x2cd/0x3d0 net/sched/cls_route.c:235
CPU: 1 PID: 15044 Comm: syz-executor.4 Not tainted 5.6.0-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:77 [inline]
dump_stack+0x1c9/0x220 lib/dump_stack.c:118
kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
__msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
route4_get+0x2cd/0x3d0 net/sched/cls_route.c:235
tc_new_tfilter+0x1f32/0x4f40 net/sched/cls_api.c:2082
rtnetlink_rcv_msg+0xcb7/0x1570 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x451/0x650 net/netlink/af_netlink.c:2478
rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5454
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0xf9e/0x1100 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x1246/0x14d0 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg net/socket.c:672 [inline]
____sys_sendmsg+0x12b6/0x1350 net/socket.c:2345
___sys_sendmsg net/socket.c:2399 [inline]
__sys_sendmsg+0x451/0x5f0 net/socket.c:2432
__compat_sys_sendmsg net/compat.c:642 [inline]
__do_compat_sys_sendmsg net/compat.c:649 [inline]
__se_compat_sys_sendmsg net/compat.c:646 [inline]
__ia32_compat_sys_sendmsg+0xed/0x130 net/compat.c:646
do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline]
do_fast_syscall_32+0x3c7/0x6e0 arch/x86/entry/common.c:410
entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f0bd99
Code: 90 e8 0b 00 00 00 f3 90 0f ae e8 eb f9 8d 74 26 00 89 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f5cc40cc EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020000280
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

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:2801 [inline]
slab_alloc mm/slub.c:2810 [inline]
kmem_cache_alloc_trace+0x6f3/0xd70 mm/slub.c:2827
kmalloc include/linux/slab.h:555 [inline]
batadv_forw_packet_alloc+0x1be/0x6d0 net/batman-adv/send.c:525
batadv_iv_ogm_aggregate_new net/batman-adv/bat_iv_ogm.c:562 [inline]
batadv_iv_ogm_queue_add+0x11cb/0x1900 net/batman-adv/bat_iv_ogm.c:670
batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:833 [inline]
batadv_iv_ogm_schedule+0xd4c/0x1430 net/batman-adv/bat_iv_ogm.c:869
batadv_iv_send_outstanding_bat_ogm_packet+0xbae/0xd50 net/batman-adv/bat_iv_ogm.c:1722
process_one_work+0x1555/0x1f40 kernel/workqueue.c:2266
worker_thread+0xef6/0x2450 kernel/workqueue.c:2412
kthread+0x4b5/0x4f0 kernel/kthread.c:256
ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:353
=====================================================


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[syzbot]

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