WARNING in tcp_enter_loss

Hello,

syzkaller hit the following crash on fb20eb9d798d2f4c1a75b7fe981d72dfa8d7270d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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


WARNING: CPU: 1 PID: 3331 at net/ipv4/tcp_input.c:1959 tcp_enter_loss+0xcd5/0xf80 net/ipv4/tcp_input.c:1959
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3331 Comm: syz-executor7 Not tainted 4.15.0-rc1-next-20171201+ #57
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
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:177
 fixup_bug arch/x86/kernel/traps.c:246 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:295
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1066
RIP: 0010:tcp_enter_loss+0xcd5/0xf80 net/ipv4/tcp_input.c:1959
RSP: 0018:ffff8801db5073f0 EFLAGS: 00010206
RAX: ffff8801c4b8a300 RBX: 0000000000000000 RCX: ffffffff84479c25
RDX: 0000000000000100 RSI: ffff8801c67877c4 RDI: ffff8801c678772c
RBP: ffff8801db507468 R08: ffff88021fff805c R09: 0000000000000000
R10: ffff88021fff8050 R11: ffff88021fff805d R12: 000000000000fe90
R13: ffff8801cc8050b0 R14: dffffc0000000000 R15: ffff8801c6786ec0
 tcp_retransmit_timer+0xcf2/0x2a00 net/ipv4/tcp_timer.c:477
 tcp_write_timer_handler+0x335/0x820 net/ipv4/tcp_timer.c:564
 tcp_write_timer+0x152/0x170 net/ipv4/tcp_timer.c:584
 call_timer_fn+0x23b/0x840 kernel/time/timer.c:1330
 expire_timers kernel/time/timer.c:1367 [inline]
 __run_timers+0x7e1/0xb60 kernel/time/timer.c:1670
 run_timer_softirq+0x4c/0x90 kernel/time/timer.c:1696
 __do_softirq+0x29d/0xbb2 kernel/softirq.c:285
 invoke_softirq kernel/softirq.c:365 [inline]
 irq_exit+0x1d3/0x210 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:907
 </IRQ>
RIP: 0010:arch_local_irq_enable arch/x86/include/asm/paravirt.h:787 [inline]
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:168 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x56/0x70 kernel/locking/spinlock.c:199
RSP: 0018:ffff8801c4b277f8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: ffff8801db527900 RCX: 0000000000000000
RDX: 1ffffffff0bd9743 RSI: 0000000000000001 RDI: ffffffff85ecba18
RBP: ffff8801c4b27800 R08: ffff8801db527918 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c1648300
R13: 1ffff10038964f08 R14: ffff8801c4b8a300 R15: ffff8801c4b8a300
 finish_lock_switch kernel/sched/sched.h:1369 [inline]
 finish_task_switch+0x1d3/0x740 kernel/sched/core.c:2667
 context_switch kernel/sched/core.c:2803 [inline]
 __schedule+0x8f3/0x2060 kernel/sched/core.c:3376
 schedule+0xf5/0x430 kernel/sched/core.c:3435
 freezable_schedule include/linux/freezer.h:172 [inline]
 do_nanosleep+0x224/0x6e0 kernel/time/hrtimer.c:1640
 hrtimer_nanosleep+0x2b2/0x860 kernel/time/hrtimer.c:1694
 SYSC_nanosleep kernel/time/hrtimer.c:1726 [inline]
 SyS_nanosleep+0x175/0x1f0 kernel/time/hrtimer.c:1713
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x47e020
RSP: 002b:0000000000a6fa08 EFLAGS: 00000246 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 0000000000c59914 RCX: 000000000047e020
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000a6fa10
RBP: 0000000000000d02 R08: 0000000000000001 R09: 0000000000c59940
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000d02
R13: 000000000000000f R14: 0000000000034718 R15: 0000000000000010
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.
Please credit me with: Reported-by: syzbot [off-list ref]

syzbot will keep track of this bug report.
Once a fix for this bug is merged into any tree, reply to this email with:
#syz fix: exact-commit-title
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.