Subject: Re: KMSAN: uninit-value in ip_vs_lblc_check_expire

From: syzbot <[email-masked]>
Date: Thu, 21 Jun 2018 22:52:02 -0700

syzbot has found a reproducer for the following crash on:

HEAD commit:    123906095e30 kmsan: introduce kmsan_interrupt_enter()/kmsa..
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=134ad890400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=848e40757852af3e
dashboard link: https://syzkaller.appspot.com/bug?extid=3e9695f147fb529aa9bc
compiler:       clang version 7.0.0 (trunk 334104)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=11505218400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1168a490400000

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

==================================================================
BUG: KMSAN: uninit-value in ip_vs_lblc_check_expire+0xe62/0xf10  
net/netfilter/ipvs/ip_vs_lblc.c:315
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.17.0+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x185/0x1d0 lib/dump_stack.c:113
  kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1125
  __msan_warning_32+0x70/0xc0 mm/kmsan/kmsan_instr.c:620
  ip_vs_lblc_check_expire+0xe62/0xf10 net/netfilter/ipvs/ip_vs_lblc.c:315
  call_timer_fn+0x280/0x5d0 kernel/time/timer.c:1326
  expire_timers kernel/time/timer.c:1363 [inline]
  __run_timers+0xd96/0x11b0 kernel/time/timer.c:1666
  run_timer_softirq+0x43/0x70 kernel/time/timer.c:1692
  __do_softirq+0x592/0x979 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x202/0x240 kernel/softirq.c:405
  exiting_irq+0xe/0x10 arch/x86/include/asm/apic.h:525
  smp_apic_timer_interrupt+0x64/0x90 arch/x86/kernel/apic/apic.c:1055
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:866
  </IRQ>
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:55 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:97 [inline]
RIP: 0010:default_idle+0x20b/0x3e0 arch/x86/kernel/process.c:500
RSP: 0018:ffff8801d8e5fdf0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff8801fd432f18 RBX: 0000000000000000 RCX: ffff880000000000
RDX: ffff8801fd032f18 RSI: aaaaaaaaaaaab000 RDI: ffffea0000000000
RBP: ffff8801d8e5fe28 R08: 0000000001080020 R09: 0000000000000002
R10: 00000030de3d75c0 R11: ffffffff89fef830 R12: ffff8801d8e5fe8f
R13: ffff8801d8da57c0 R14: ffff8801d8e5fe8c R15: ffff8801d8da6098
  arch_cpu_idle+0x26/0x30 arch/x86/kernel/process.c:491
  default_idle_call kernel/sched/idle.c:93 [inline]
  cpuidle_idle_call kernel/sched/idle.c:153 [inline]
  do_idle+0x36d/0x830 kernel/sched/idle.c:262
  cpu_startup_entry+0x45/0x50 kernel/sched/idle.c:368
  start_secondary+0x3c6/0x490 arch/x86/kernel/smpboot.c:272
  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:282 [inline]
  kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:819
  kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:889
  __alloc_pages_nodemask+0xf7b/0x5cc0 mm/page_alloc.c:4402
  alloc_pages_current+0x6b1/0x970 mm/mempolicy.c:2093
  alloc_pages include/linux/gfp.h:494 [inline]
  kmalloc_order mm/slab_common.c:1148 [inline]
  kmalloc_order_trace+0xbb/0x390 mm/slab_common.c:1159
  kmalloc_large include/linux/slab.h:446 [inline]
  __kmalloc+0x335/0x350 mm/slub.c:3805
  kmalloc include/linux/slab.h:517 [inline]
  ip_vs_lblc_init_svc+0x57/0x310 net/netfilter/ipvs/ip_vs_lblc.c:355
  ip_vs_bind_scheduler+0xa9/0x1f0 net/netfilter/ipvs/ip_vs_sched.c:51
  ip_vs_add_service+0xa9d/0x1d90 net/netfilter/ipvs/ip_vs_ctl.c:1265
  do_ip_vs_set_ctl+0x2aa9/0x2cd0 net/netfilter/ipvs/ip_vs_ctl.c:2462
  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
  nf_setsockopt+0x47c/0x4e0 net/netfilter/nf_sockopt.c:115
  ip_setsockopt+0x24b/0x2b0 net/ipv4/ip_sockglue.c:1251
  udp_setsockopt+0x108/0x1b0 net/ipv4/udp.c:2416
  ipv6_setsockopt+0x311/0x350 net/ipv6/ipv6_sockglue.c:917
  tcp_setsockopt+0x1c0/0x1f0 net/ipv4/tcp.c:2891
  sock_common_setsockopt+0x13b/0x170 net/core/sock.c:3039
  __sys_setsockopt+0x496/0x540 net/socket.c:1903
  __do_sys_setsockopt net/socket.c:1914 [inline]
  __se_sys_setsockopt net/socket.c:1911 [inline]
  __x64_sys_setsockopt+0x15c/0x1c0 net/socket.c:1911
  do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
==================================================================