Subject: suspicious RCU usage at net/ipv6/ip6_fib.c:LINE

From: syzbot <[email-masked]>
Date: Tue, 02 Jan 2018 15:58:02 -0800

Hello,

syzkaller hit the following crash on  
6bb8824732f69de0f233ae6b1a8158e149627b38
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

=============================
WARNING: suspicious RCU usage
4.15.0-rc5+ #171 Not tainted
-----------------------------
net/ipv6/ip6_fib.c:1702 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
4 locks held by swapper/0/0:
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
lockdep_copy_map include/linux/lockdep.h:178 [inline]
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
call_timer_fn+0x1c6/0x820 kernel/time/timer.c:1310
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
fib6_run_gc+0x9d/0x3c0 net/ipv6/ip6_fib.c:2007
  #2:  (rcu_read_lock){....}, at: [<0000000091db762d>]  
__fib6_clean_all+0x0/0x3a0 net/ipv6/ip6_fib.c:1560
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
__fib6_clean_all+0x1d0/0x3a0 net/ipv6/ip6_fib.c:1948

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc5+ #171
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
  fib6_del+0xcaa/0x11b0 net/ipv6/ip6_fib.c:1701
  fib6_clean_node+0x3aa/0x4f0 net/ipv6/ip6_fib.c:1892
  fib6_walk_continue+0x46c/0x8a0 net/ipv6/ip6_fib.c:1815
  fib6_walk+0x91/0xf0 net/ipv6/ip6_fib.c:1863
  fib6_clean_tree+0x1e6/0x340 net/ipv6/ip6_fib.c:1933
  __fib6_clean_all+0x1f4/0x3a0 net/ipv6/ip6_fib.c:1949
  fib6_clean_all net/ipv6/ip6_fib.c:1960 [inline]
  fib6_run_gc+0x16b/0x3c0 net/ipv6/ip6_fib.c:2016
  fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2033
  call_timer_fn+0x228/0x820 kernel/time/timer.c:1320
  expire_timers kernel/time/timer.c:1357 [inline]
  __run_timers+0x7ee/0xb70 kernel/time/timer.c:1660
  run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1cc/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:540 [inline]
  smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:904
  </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffffffff86407c38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 1ffffffff0c80f8a RCX: 0000000000000000
RDX: 1ffffffff0c99048 RSI: 0000000000000001 RDI: ffffffff864c8240
RBP: ffffffff86407c38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff86407cf0 R14: ffffffff86c329a0 R15: 0000000000000000
  arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline]
  default_idle+0xbf/0x460 arch/x86/kernel/process.c:355
  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346
  default_idle_call+0x36/0x90 kernel/sched/idle.c:98
  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
  do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
  cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351
  rest_init+0xed/0xf0 init/main.c:435
  start_kernel+0x7f1/0x819 init/main.c:713
  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
  x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237

=============================
WARNING: suspicious RCU usage
4.15.0-rc5+ #171 Not tainted
-----------------------------
net/ipv6/ip6_fib.c:1729 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
4 locks held by swapper/0/0:
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
lockdep_copy_map include/linux/lockdep.h:178 [inline]
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
call_timer_fn+0x1c6/0x820 kernel/time/timer.c:1310
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
fib6_run_gc+0x9d/0x3c0 net/ipv6/ip6_fib.c:2007
  #2:  (rcu_read_lock){....}, at: [<0000000091db762d>]  
__fib6_clean_all+0x0/0x3a0 net/ipv6/ip6_fib.c:1560
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
__fib6_clean_all+0x1d0/0x3a0 net/ipv6/ip6_fib.c:1948

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc5+ #171
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
  fib6_del+0x425/0x11b0 net/ipv6/ip6_fib.c:1728
  fib6_clean_node+0x3aa/0x4f0 net/ipv6/ip6_fib.c:1892
  fib6_walk_continue+0x46c/0x8a0 net/ipv6/ip6_fib.c:1815
  fib6_walk+0x91/0xf0 net/ipv6/ip6_fib.c:1863
  fib6_clean_tree+0x1e6/0x340 net/ipv6/ip6_fib.c:1933
  __fib6_clean_all+0x1f4/0x3a0 net/ipv6/ip6_fib.c:1949
  fib6_clean_all net/ipv6/ip6_fib.c:1960 [inline]
  fib6_run_gc+0x16b/0x3c0 net/ipv6/ip6_fib.c:2016
  fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2033
  call_timer_fn+0x228/0x820 kernel/time/timer.c:1320
  expire_timers kernel/time/timer.c:1357 [inline]
  __run_timers+0x7ee/0xb70 kernel/time/timer.c:1660
  run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1cc/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:540 [inline]
  smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:904
  </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffffffff86407c38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 1ffffffff0c80f8a RCX: 0000000000000000
RDX: 1ffffffff0c99048 RSI: 0000000000000001 RDI: ffffffff864c8240
RBP: ffffffff86407c38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff86407cf0 R14: ffffffff86c329a0 R15: 0000000000000000
  arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline]
  default_idle+0xbf/0x460 arch/x86/kernel/process.c:355
  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346
  default_idle_call+0x36/0x90 kernel/sched/idle.c:98
  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
  do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
  cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351
  rest_init+0xed/0xf0 init/main.c:435
  start_kernel+0x7f1/0x819 init/main.c:713
  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
  x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237

=============================
WARNING: suspicious RCU usage
4.15.0-rc5+ #171 Not tainted
-----------------------------
net/ipv6/ip6_fib.c:1639 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
4 locks held by swapper/0/0:
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
lockdep_copy_map include/linux/lockdep.h:178 [inline]
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
call_timer_fn+0x1c6/0x820 kernel/time/timer.c:1310
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
fib6_run_gc+0x9d/0x3c0 net/ipv6/ip6_fib.c:2007
  #2:  (rcu_read_lock){....}, at: [<0000000091db762d>]  
__fib6_clean_all+0x0/0x3a0 net/ipv6/ip6_fib.c:1560
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
__fib6_clean_all+0x1d0/0x3a0 net/ipv6/ip6_fib.c:1948

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc5+ #171
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
  fib6_del_route net/ipv6/ip6_fib.c:1638 [inline]
  fib6_del+0xd18/0x11b0 net/ipv6/ip6_fib.c:1731
  fib6_clean_node+0x3aa/0x4f0 net/ipv6/ip6_fib.c:1892
  fib6_walk_continue+0x46c/0x8a0 net/ipv6/ip6_fib.c:1815
  fib6_walk+0x91/0xf0 net/ipv6/ip6_fib.c:1863
  fib6_clean_tree+0x1e6/0x340 net/ipv6/ip6_fib.c:1933
  __fib6_clean_all+0x1f4/0x3a0 net/ipv6/ip6_fib.c:1949
  fib6_clean_all net/ipv6/ip6_fib.c:1960 [inline]
  fib6_run_gc+0x16b/0x3c0 net/ipv6/ip6_fib.c:2016
  fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2033
  call_timer_fn+0x228/0x820 kernel/time/timer.c:1320
  expire_timers kernel/time/timer.c:1357 [inline]
  __run_timers+0x7ee/0xb70 kernel/time/timer.c:1660
  run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1cc/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:540 [inline]
  smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:904
  </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffffffff86407c38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 1ffffffff0c80f8a RCX: 0000000000000000
RDX: 1ffffffff0c99048 RSI: 0000000000000001 RDI: ffffffff864c8240
RBP: ffffffff86407c38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff86407cf0 R14: ffffffff86c329a0 R15: 0000000000000000
  arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline]
  default_idle+0xbf/0x460 arch/x86/kernel/process.c:355
  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346
  default_idle_call+0x36/0x90 kernel/sched/idle.c:98
  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
  do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
  cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351
  rest_init+0xed/0xf0 init/main.c:435
  start_kernel+0x7f1/0x819 init/main.c:713
  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
  x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237

=============================
WARNING: suspicious RCU usage
4.15.0-rc5+ #171 Not tainted
-----------------------------
net/ipv6/ip6_fib.c:1676 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
5 locks held by swapper/0/0:
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
lockdep_copy_map include/linux/lockdep.h:178 [inline]
  #0:  ((&net->ipv6.ip6_fib_timer)){+.-.}, at: [<00000000d43f631b>]  
call_timer_fn+0x1c6/0x820 kernel/time/timer.c:1310
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-.}, at: [<000000002ff9d65c>]  
fib6_run_gc+0x9d/0x3c0 net/ipv6/ip6_fib.c:2007
  #2:  (rcu_read_lock){....}, at: [<0000000091db762d>]  
__fib6_clean_all+0x0/0x3a0 net/ipv6/ip6_fib.c:1560
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
spin_lock_bh include/linux/spinlock.h:315 [inline]
  #3:  (&(&tb->tb6_lock)->rlock){+.-.}, at: [<000000009e503581>]  
__fib6_clean_all+0x1d0/0x3a0 net/ipv6/ip6_fib.c:1948
  #4:  (&net->ipv6.fib6_walker_lock){++--}, at: [<0000000003fbce86>]  
fib6_del_route net/ipv6/ip6_fib.c:1671 [inline]
  #4:  (&net->ipv6.fib6_walker_lock){++--}, at: [<0000000003fbce86>]  
fib6_del+0x935/0x11b0 net/ipv6/ip6_fib.c:1731

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc5+ #171
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
  fib6_del_route net/ipv6/ip6_fib.c:1675 [inline]
  fib6_del+0xeb3/0x11b0 net/ipv6/ip6_fib.c:1731
  fib6_clean_node+0x3aa/0x4f0 net/ipv6/ip6_fib.c:1892
  fib6_walk_continue+0x46c/0x8a0 net/ipv6/ip6_fib.c:1815
  fib6_walk+0x91/0xf0 net/ipv6/ip6_fib.c:1863
  fib6_clean_tree+0x1e6/0x340 net/ipv6/ip6_fib.c:1933
  __fib6_clean_all+0x1f4/0x3a0 net/ipv6/ip6_fib.c:1949
  fib6_clean_all net/ipv6/ip6_fib.c:1960 [inline]
  fib6_run_gc+0x16b/0x3c0 net/ipv6/ip6_fib.c:2016
  fib6_gc_timer_cb+0x20/0x30 net/ipv6/ip6_fib.c:2033
  call_timer_fn+0x228/0x820 kernel/time/timer.c:1320
  expire_timers kernel/time/timer.c:1357 [inline]
  __run_timers+0x7ee/0xb70 kernel/time/timer.c:1660
  run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1cc/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:540 [inline]
  smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:904
  </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54
RSP: 0018:ffffffff86407c38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 1ffffffff0c80f8a RCX: 0000000000000000
RDX: 1ffffffff0c99048 RSI: 0000000000000001 RDI: ffffffff864c8240
RBP: ffffffff86407c38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff86407cf0 R14: ffffffff86c329a0 R15: 0000000000000000
  arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline]
  default_idle+0xbf/0x460 arch/x86/kernel/process.c:355
  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346
  default_idle_call+0x36/0x90 kernel/sched/idle.c:98
  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
  do_idle+0x24a/0x3b0 kernel/sched/idle.c:246
  cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351
  rest_init+0xed/0xf0 init/main.c:435
  start_kernel+0x7f1/0x819 init/main.c:713
  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
  x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
  secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237

---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to [email-masked].

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.