WARNING in fpu__restore

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e0b05e69 ANDROID: kbuild: change LTO into a choice
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=10951843800000
kernel config: https://syzkaller.appspot.com/x/.config?x=5d2b94b08f1123d
dashboard link: https://syzkaller.appspot.com/bug?extid=85f094b32e873e09177a
compiler: gcc (GCC) 7.1.1 20170620
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=172d84e3800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+85f094...@syzkaller.appspotmail.com

IPVS: Creating netns size=2536 id=5
IPVS: Creating netns size=2536 id=6
IPVS: Creating netns size=2536 id=7
IPVS: Creating netns size=2536 id=8
------------[ cut here ]------------
WARNING: CPU: 0 PID: 22298 at ./arch/x86/include/asm/fpu/internal.h:534
__fpregs_activate arch/x86/include/asm/fpu/internal.h:534 [inline]
WARNING: CPU: 0 PID: 22298 at ./arch/x86/include/asm/fpu/internal.h:534
fpregs_activate arch/x86/include/asm/fpu/internal.h:566 [inline]
WARNING: CPU: 0 PID: 22298 at ./arch/x86/include/asm/fpu/internal.h:534
fpu__restore+0x6b6/0x8c0 arch/x86/kernel/fpu/core.c:461
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 22298 Comm: syz-executor0 Not tainted 4.9.85-ge0b05e6 #57
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801d468fa98 ffffffff81d95739 ffffffff83a480c0 ffff8801d468fb70
ffffffff83a1e200 ffffffff8106e4b6 0000000000000009 ffff8801d468fb60
ffffffff8142f581 0000000041b58ab3 ffffffff8418b1f0 ffffffff8142f3c5
Call Trace:
[<ffffffff81d95739>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81d95739>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff8142f581>] panic+0x1bc/0x3a8 kernel/panic.c:179
[<ffffffff811311c4>] __warn+0x1c4/0x1e0 kernel/panic.c:542
[<ffffffff8113142c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
[<ffffffff8106e4b6>] __fpregs_activate
arch/x86/include/asm/fpu/internal.h:534 [inline]
[<ffffffff8106e4b6>] fpregs_activate
arch/x86/include/asm/fpu/internal.h:566 [inline]
[<ffffffff8106e4b6>] fpu__restore+0x6b6/0x8c0
arch/x86/kernel/fpu/core.c:461
[<ffffffff81072d98>] __fpu__restore_sig+0x3d8/0x1330
arch/x86/kernel/fpu/signal.c:349
[<ffffffff81074217>] fpu__restore_sig+0x87/0xe0
arch/x86/kernel/fpu/signal.c:388
[<ffffffff8111d9e1>] ia32_restore_sigcontext+0x3d1/0x490
arch/x86/ia32/ia32_signal.c:108
[<ffffffff8111e415>] sys32_rt_sigreturn+0x1d5/0x290
arch/x86/ia32/ia32_signal.c:156
[<ffffffff81006f95>] do_syscall_32_irqs_on arch/x86/entry/common.c:325
[inline]
[<ffffffff81006f95>] do_fast_syscall_32+0x2f5/0x870
arch/x86/entry/common.c:387
[<ffffffff838b6b10>] entry_SYSENTER_compat+0x90/0xa2
arch/x86/entry/entry_64_compat.S:137
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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