Re: [syzbot] WARNING in ex_handler_fprestore

[syzbot <syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    8124c8a6 Linux 5.13-rc4
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1047c4a7d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=71698168f5f17484
dashboard link: https://syzkaller.appspot.com/bug?extid=2067e764dbcd10721e2e
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1020b26bd00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12afa2a7d00000

The issue was bisected to:

commit b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94
Author: Fenghua Yu <fenghua.yu@intel.com>
Date:   Tue May 12 14:54:39 2020 +0000

    x86/fpu/xstate: Define new functions for clearing fpregs and xstates

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17c2c723d00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1422c723d00000
console output: https://syzkaller.appspot.com/x/log.txt?x=1022c723d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com
Fixes: b860eb8dce59 ("x86/fpu/xstate: Define new functions for clearing fpregs and xstates")

syz-executor638[9087] bad frame in rt_sigreturn frame:00007f1dcdbbdbf8 ip:445bf9 sp:7f1dcdbbe188 orax:ffffffffffffffff in syz-executor638076058[401000+9a000]
------------[ cut here ]------------
Bad FPU state detected at copy_kernel_to_xregs arch/x86/include/asm/fpu/internal.h:344 [inline], reinitializing FPU registers.
Bad FPU state detected at __copy_kernel_to_fpregs arch/x86/include/asm/fpu/internal.h:419 [inline], reinitializing FPU registers.
Bad FPU state detected at copy_kernel_to_fpregs arch/x86/include/asm/fpu/internal.h:443 [inline], reinitializing FPU registers.
Bad FPU state detected at __fpregs_load_activate arch/x86/include/asm/fpu/internal.h:514 [inline], reinitializing FPU registers.
Bad FPU state detected at copy_fpstate_to_sigframe+0x4d2/0xae0 arch/x86/kernel/fpu/signal.c:191, reinitializing FPU registers.
WARNING: CPU: 1 PID: 9087 at arch/x86/mm/extable.c:65 ex_handler_fprestore+0xf0/0x110 arch/x86/mm/extable.c:65
Modules linked in:
CPU: 1 PID: 9087 Comm: syz-executor638 Not tainted 5.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ex_handler_fprestore+0xf0/0x110 arch/x86/mm/extable.c:65
Code: e8 55 40 40 00 b8 01 00 00 00 5b 5d 41 5c c3 e8 46 40 40 00 48 89 de 48 c7 c7 c0 0c 69 89 c6 05 42 12 81 0c 01 e8 db 48 a1 07 <0f> 0b eb 90 48 89 df e8 94 c8 84 00 e9 3d ff ff ff e8 1a c9 84 00
RSP: 0018:ffffc9000227fa60 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffff812aeeb2 RCX: 0000000000000000
RDX: ffff88803031a100 RSI: ffffffff815c1805 RDI: fffff5200044ff3e
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bb63e R11: 0000000000000000 R12: ffffffff8b23f7d8
R13: 000000000000000d R14: 0000000000000000 R15: 0000000000000000
FS:  00007f1dcdbbe700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000000 CR3: 0000000031055000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 fixup_exception+0x9a/0xd0 arch/x86/mm/extable.c:183
 __exc_general_protection arch/x86/kernel/traps.c:567 [inline]
 exc_general_protection+0xed/0x2f0 arch/x86/kernel/traps.c:531
 asm_exc_general_protection+0x1e/0x30 arch/x86/include/asm/idtentry.h:571
RIP: 0010:__fpregs_load_activate arch/x86/include/asm/fpu/internal.h:514 [inline]
RIP: 0010:copy_fpstate_to_sigframe+0x4d2/0xae0 arch/x86/kernel/fpu/signal.c:191
Code: 58 e8 d2 22 49 00 48 c7 c0 c0 29 c9 8d 0f 1f 44 00 00 e8 c1 22 49 00 e8 bc 22 49 00 b8 ff ff ff ff 4c 89 e7 89 c2 48 0f ae 2f <e8> a9 22 49 00 65 4c 89 35 d1 00 d7 7e 0f 1f 44 00 00 e8 97 22 49
RSP: 0018:ffffc9000227fc08 EFLAGS: 00010293
RAX: 00000000ffffffff RBX: ffff88803031a100 RCX: 0000000000000000
RDX: 00000000ffffffff RSI: ffffffff812aeea4 RDI: ffff88803031b900
RBP: ffff88803031a100 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff812aee3b R11: 0000000000000000 R12: ffff88803031b900
R13: ffffed10060636f2 R14: ffff88803031b8c0 R15: 00007f1dcdbbddc0
 get_sigframe.constprop.0.isra.0+0x429/0x730 arch/x86/kernel/signal.c:274
 __setup_rt_frame arch/x86/kernel/signal.c:450 [inline]
 setup_rt_frame arch/x86/kernel/signal.c:702 [inline]
 handle_signal arch/x86/kernel/signal.c:746 [inline]
 arch_do_signal_or_restart+0xd9e/0x1eb0 arch/x86/kernel/signal.c:791
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x171/0x280 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:57
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445bf9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1dcdbbe188 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 00000000004cb408 RCX: 0000000000445bf9
RDX: 0000000080000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000004cb400 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cb40c
R13: 00007ffcd24a5bdf R14: 00007f1dcdbbe300 R15: 0000000000022000