* WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
@ 2016-02-11 19:27 Borislav Petkov
2016-02-11 23:47 ` Andy Lutomirski
0 siblings, 1 reply; 15+ messages in thread
From: Borislav Petkov @ 2016-02-11 19:27 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: x86-ml, lkml
Hey Andy,
can you make any sense of this:
[ 90.573923] ------------[ cut here ]------------
[ 90.574977] WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
[ 90.576108] Modules linked in: hid_generic usbhid hid snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic iTCO_wdt iTCO_vendor_support arc4 x86_pkg_temp_thermal coretemp kvm_intel kvm irqbypass crc32_pclmul crc32c_intel iwldvm mac80211 aesni_intel xts snd_hda_intel input_leds aes_i586 snd_hda_codec sdhci_pci lrw iwlwifi snd_hwdep gf128mul snd_hda_core ablk_helper cryptd ehci_pci pcspkr serio_raw xhci_pci sdhci snd_pcm sg mmc_core i2c_i801 cfg80211 lpc_ich mfd_core e1000e snd_timer ehci_hcd xhci_hcd thinkpad_acpi nvram wmi snd battery soundcore led_class ac thermal
[ 90.580570] CPU: 0 PID: 3031 Comm: bash Not tainted 4.5.0-rc3+ #1
[ 90.581380] Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012
[ 90.582325] 00000000 00000286 f158be4c c12cce56 00000000 00000000 f158be80 c10567fb
[ 90.583179] c1866c2c 00000000 00000bd7 c1859e8c 00000212 c1025ab0 00000212 c1025ab0
[ 90.584142] f2012b00 f2011f00 f2012d80 f158be90 c10568d2 00000009 00000000 f158bea4
[ 90.585002] Call Trace:
[ 90.585854] [<c12cce56>] dump_stack+0x5f/0x89
[ 90.586703] [<c10567fb>] warn_slowpath_common+0x8b/0xc0
[ 90.587559] [<c1025ab0>] ? fpu__restore+0x90/0x130
[ 90.588520] [<c1025ab0>] ? fpu__restore+0x90/0x130
[ 90.589353] [<c10568d2>] warn_slowpath_null+0x22/0x30
[ 90.590175] [<c1025ab0>] fpu__restore+0x90/0x130
[ 90.590993] [<c1027098>] __fpu__restore_sig+0x268/0x4c0
[ 90.591816] [<c102751f>] fpu__restore_sig+0x2f/0x50
[ 90.592636] [<c101a6c9>] restore_sigcontext+0xe9/0x110
[ 90.593449] [<c101af3c>] sys_sigreturn+0x9c/0xb0
[ 90.594263] [<c1001bd9>] do_syscall_32_irqs_on+0x59/0x340
[ 90.595079] [<c169979d>] entry_INT80_32+0x31/0x31
[ 90.595922] ---[ end trace be617bef2982f473 ]---
This is rc3 + latest tip/master and it happened when I did "make
mrproper" in the kernel repo.
>From a quick stare, it looks to me we're running do_syscall_32_irqs_on()
with IRQs on, sys_sigreturn() does current_pt_regs() but
__fpu__restore_sig() derefs current again and could be that that second
"current" is another current which already has ->fpregs_active set ?
FPU + signal handling code in a single backtrace. My favourite!
:-\
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-11 19:27 WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130() Borislav Petkov
@ 2016-02-11 23:47 ` Andy Lutomirski
2016-02-12 1:16 ` Andy Lutomirski
2016-02-12 11:17 ` Borislav Petkov
0 siblings, 2 replies; 15+ messages in thread
From: Andy Lutomirski @ 2016-02-11 23:47 UTC (permalink / raw)
To: Borislav Petkov; +Cc: x86-ml, lkml
On Thu, Feb 11, 2016 at 11:27 AM, Borislav Petkov <bp@alien8.de> wrote:
> Hey Andy,
>
> can you make any sense of this:
>
> [ 90.573923] ------------[ cut here ]------------
> [ 90.574977] WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
> [ 90.576108] Modules linked in: hid_generic usbhid hid snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic iTCO_wdt iTCO_vendor_support arc4 x86_pkg_temp_thermal coretemp kvm_intel kvm irqbypass crc32_pclmul crc32c_intel iwldvm mac80211 aesni_intel xts snd_hda_intel input_leds aes_i586 snd_hda_codec sdhci_pci lrw iwlwifi snd_hwdep gf128mul snd_hda_core ablk_helper cryptd ehci_pci pcspkr serio_raw xhci_pci sdhci snd_pcm sg mmc_core i2c_i801 cfg80211 lpc_ich mfd_core e1000e snd_timer ehci_hcd xhci_hcd thinkpad_acpi nvram wmi snd battery soundcore led_class ac thermal
> [ 90.580570] CPU: 0 PID: 3031 Comm: bash Not tainted 4.5.0-rc3+ #1
> [ 90.581380] Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012
> [ 90.582325] 00000000 00000286 f158be4c c12cce56 00000000 00000000 f158be80 c10567fb
> [ 90.583179] c1866c2c 00000000 00000bd7 c1859e8c 00000212 c1025ab0 00000212 c1025ab0
> [ 90.584142] f2012b00 f2011f00 f2012d80 f158be90 c10568d2 00000009 00000000 f158bea4
> [ 90.585002] Call Trace:
> [ 90.585854] [<c12cce56>] dump_stack+0x5f/0x89
> [ 90.586703] [<c10567fb>] warn_slowpath_common+0x8b/0xc0
> [ 90.587559] [<c1025ab0>] ? fpu__restore+0x90/0x130
> [ 90.588520] [<c1025ab0>] ? fpu__restore+0x90/0x130
> [ 90.589353] [<c10568d2>] warn_slowpath_null+0x22/0x30
> [ 90.590175] [<c1025ab0>] fpu__restore+0x90/0x130
> [ 90.590993] [<c1027098>] __fpu__restore_sig+0x268/0x4c0
> [ 90.591816] [<c102751f>] fpu__restore_sig+0x2f/0x50
> [ 90.592636] [<c101a6c9>] restore_sigcontext+0xe9/0x110
> [ 90.593449] [<c101af3c>] sys_sigreturn+0x9c/0xb0
> [ 90.594263] [<c1001bd9>] do_syscall_32_irqs_on+0x59/0x340
> [ 90.595079] [<c169979d>] entry_INT80_32+0x31/0x31
> [ 90.595922] ---[ end trace be617bef2982f473 ]---
>
> This is rc3 + latest tip/master and it happened when I did "make
> mrproper" in the kernel repo.
>
> From a quick stare, it looks to me we're running do_syscall_32_irqs_on()
> with IRQs on, sys_sigreturn() does current_pt_regs() but
> __fpu__restore_sig() derefs current again and could be that that second
> "current" is another current which already has ->fpregs_active set ?
>
> FPU + signal handling code in a single backtrace. My favourite!
>
> :-\
Ugh.
Can you send all the fpu info that the kernel prints really early when it boots?
--Andy
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-11 23:47 ` Andy Lutomirski
@ 2016-02-12 1:16 ` Andy Lutomirski
2016-02-12 17:00 ` Borislav Petkov
2016-02-15 19:05 ` Borislav Petkov
2016-02-12 11:17 ` Borislav Petkov
1 sibling, 2 replies; 15+ messages in thread
From: Andy Lutomirski @ 2016-02-12 1:16 UTC (permalink / raw)
To: Borislav Petkov; +Cc: x86-ml, lkml
On Thu, Feb 11, 2016 at 3:47 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Thu, Feb 11, 2016 at 11:27 AM, Borislav Petkov <bp@alien8.de> wrote:
>> Hey Andy,
>>
>> can you make any sense of this:
>>
>> [ 90.573923] ------------[ cut here ]------------
>> [ 90.574977] WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
>> [ 90.576108] Modules linked in: hid_generic usbhid hid snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic iTCO_wdt iTCO_vendor_support arc4 x86_pkg_temp_thermal coretemp kvm_intel kvm irqbypass crc32_pclmul crc32c_intel iwldvm mac80211 aesni_intel xts snd_hda_intel input_leds aes_i586 snd_hda_codec sdhci_pci lrw iwlwifi snd_hwdep gf128mul snd_hda_core ablk_helper cryptd ehci_pci pcspkr serio_raw xhci_pci sdhci snd_pcm sg mmc_core i2c_i801 cfg80211 lpc_ich mfd_core e1000e snd_timer ehci_hcd xhci_hcd thinkpad_acpi nvram wmi snd battery soundcore led_class ac thermal
>> [ 90.580570] CPU: 0 PID: 3031 Comm: bash Not tainted 4.5.0-rc3+ #1
>> [ 90.581380] Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012
>> [ 90.582325] 00000000 00000286 f158be4c c12cce56 00000000 00000000 f158be80 c10567fb
>> [ 90.583179] c1866c2c 00000000 00000bd7 c1859e8c 00000212 c1025ab0 00000212 c1025ab0
>> [ 90.584142] f2012b00 f2011f00 f2012d80 f158be90 c10568d2 00000009 00000000 f158bea4
>> [ 90.585002] Call Trace:
>> [ 90.585854] [<c12cce56>] dump_stack+0x5f/0x89
>> [ 90.586703] [<c10567fb>] warn_slowpath_common+0x8b/0xc0
>> [ 90.587559] [<c1025ab0>] ? fpu__restore+0x90/0x130
>> [ 90.588520] [<c1025ab0>] ? fpu__restore+0x90/0x130
>> [ 90.589353] [<c10568d2>] warn_slowpath_null+0x22/0x30
>> [ 90.590175] [<c1025ab0>] fpu__restore+0x90/0x130
>> [ 90.590993] [<c1027098>] __fpu__restore_sig+0x268/0x4c0
>> [ 90.591816] [<c102751f>] fpu__restore_sig+0x2f/0x50
>> [ 90.592636] [<c101a6c9>] restore_sigcontext+0xe9/0x110
>> [ 90.593449] [<c101af3c>] sys_sigreturn+0x9c/0xb0
>> [ 90.594263] [<c1001bd9>] do_syscall_32_irqs_on+0x59/0x340
>> [ 90.595079] [<c169979d>] entry_INT80_32+0x31/0x31
>> [ 90.595922] ---[ end trace be617bef2982f473 ]---
>>
>> This is rc3 + latest tip/master and it happened when I did "make
>> mrproper" in the kernel repo.
>>
>> From a quick stare, it looks to me we're running do_syscall_32_irqs_on()
>> with IRQs on, sys_sigreturn() does current_pt_regs() but
>> __fpu__restore_sig() derefs current again and could be that that second
>> "current" is another current which already has ->fpregs_active set ?
>>
>> FPU + signal handling code in a single backtrace. My favourite!
>>
>> :-\
>
> Ugh.
>
> Can you send all the fpu info that the kernel prints really early when it boots?
>
Are you running 32-bit userspace by any chance? I'm guessing you're
hitting this in __fpu_restore_sig:
fpu__drop(fpu);
if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) ||
__copy_from_user(&env, buf, sizeof(env))) {
fpstate_init(&fpu->state);
err = -1;
} else {
sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
}
fpu->fpstate_active = 1;
<-- preempted right here
if (use_eager_fpu()) {
preempt_disable();
fpu__restore(fpu);
preempt_enable();
}
I don't see why this code deserves to work. If I'm right, it can be
fixed by pulling the preempt_disable out of the if (use_eager_fpu())
to right above the fpstate_active = 1 line. Don't bother trying to
optimize the !use_eager_fpu() case.
Once someone gets around to eagerly *allocating* the FPU context and
dropping CR0.TS usage entirely, then even that won't be enough unless
we do my suggesting of deferring FPU restore to
prepare_exit_to_usermode. (Doing that will make all of this much,
much more sane.)
--Andy
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-11 23:47 ` Andy Lutomirski
2016-02-12 1:16 ` Andy Lutomirski
@ 2016-02-12 11:17 ` Borislav Petkov
1 sibling, 0 replies; 15+ messages in thread
From: Borislav Petkov @ 2016-02-12 11:17 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: x86-ml, lkml
On Thu, Feb 11, 2016 at 03:47:12PM -0800, Andy Lutomirski wrote:
> Can you send all the fpu info that the kernel prints really early when it boots?
$ dmesg | grep -i fpu
[ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x01: 'x87 floating point registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x02: 'SSE registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x04: 'AVX registers'
[ 0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
[ 0.000000] x86/fpu: Using 'eager' FPU context switches.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-12 1:16 ` Andy Lutomirski
@ 2016-02-12 17:00 ` Borislav Petkov
2016-02-15 19:14 ` Borislav Petkov
2016-02-15 19:05 ` Borislav Petkov
1 sibling, 1 reply; 15+ messages in thread
From: Borislav Petkov @ 2016-02-12 17:00 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: x86-ml, lkml
On Thu, Feb 11, 2016 at 05:16:00PM -0800, Andy Lutomirski wrote:
> fpu__drop(fpu);
> if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) ||
> __copy_from_user(&env, buf, sizeof(env))) {
> fpstate_init(&fpu->state);
> err = -1;
> } else {
> sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
> }
>
> fpu->fpstate_active = 1;
>
> <-- preempted right here
>From IRC:
<amluto> you could try sticking a schedule() right after that fpu->fpstate_active = 1; line
> if (use_eager_fpu()) {
> preempt_disable();
> fpu__restore(fpu);
> preempt_enable();
Something for me to try when I get a chance.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-12 1:16 ` Andy Lutomirski
2016-02-12 17:00 ` Borislav Petkov
@ 2016-02-15 19:05 ` Borislav Petkov
1 sibling, 0 replies; 15+ messages in thread
From: Borislav Petkov @ 2016-02-15 19:05 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: x86-ml, lkml
On Thu, Feb 11, 2016 at 05:16:00PM -0800, Andy Lutomirski wrote:
> Are you running 32-bit userspace by any chance?
Sure, that's a 32-bit kernel testing partition. :)
> I'm guessing you're hitting this in __fpu_restore_sig:
Yeah, I was looking at that too.
> fpu__drop(fpu);
> if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) ||
> __copy_from_user(&env, buf, sizeof(env))) {
> fpstate_init(&fpu->state);
> err = -1;
> } else {
> sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
> }
>
> fpu->fpstate_active = 1;
>
> <-- preempted right here
Yeah, that could explain why I'm seeing it.
> if (use_eager_fpu()) {
> preempt_disable();
> fpu__restore(fpu);
> preempt_enable();
> }
>
> I don't see why this code deserves to work. If I'm right, it can be
> fixed by pulling the preempt_disable out of the if (use_eager_fpu())
> to right above the fpstate_active = 1 line. Don't bother trying to
> optimize the !use_eager_fpu() case.
Right.
> Once someone gets around to eagerly *allocating* the FPU context and
> dropping CR0.TS usage entirely, then even that won't be enough unless
> we do my suggesting of deferring FPU restore to
> prepare_exit_to_usermode. (Doing that will make all of this much,
> much more sane.)
Sounds good to me.
So the thing with this issue is, is that I don't have a reproducer yet.
It happened randomly.
So let me ask it this way: can anything go wrong if we pull up the
preemption disabled region? I mean, do we even care about the !eager FPU
case? I'd much prefer that vs FPU state corruption...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-12 17:00 ` Borislav Petkov
@ 2016-02-15 19:14 ` Borislav Petkov
2016-02-16 2:25 ` Andy Lutomirski
0 siblings, 1 reply; 15+ messages in thread
From: Borislav Petkov @ 2016-02-15 19:14 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: x86-ml, lkml
On Fri, Feb 12, 2016 at 06:00:10PM +0100, Borislav Petkov wrote:
> Something for me to try when I get a chance.
Ok, so I wanted to know what happens in detail. Here's some ftracing
(debug patch at the end).
Now pay attention to this udevadm thing
[ 3.816977] rcu_pree-7 0d..2 4058241us : __switch_to: prev: rcu_preempt <-> next: udevadm
[ 3.816977] rcu_pree-7 0d..2 4058241us : __switch_to: set ->fpregs_active
[ 3.816977] udevadm-982 0.... 4058258us : __fpu__restore_sig: fpregs_active 0, f443d7c0
We're in __fpu__restore_sig() about to call schedule()
[ 3.816977] udevadm-982 0d..2 4058260us : __switch_to: prev: udevadm <-> next: usb_id
[ 3.816977] udevadm-982 0d..2 4058260us : __switch_to: set ->fpregs_active
[ 3.816977] usb_id-987 0d..2 4059684us : __switch_to: prev: usb_id <-> next: udevd
[ 3.816977] usb_id-987 0d..2 4059685us : __switch_to: set ->fpregs_active
[ 3.816977] udevd-843 0d..2 4059697us : __switch_to: prev: udevd <-> next: udevd
[ 3.816977] udevd-843 0d..2 4059697us : __switch_to: set ->fpregs_active
[ 3.816977] alsa-uti-989 0d..2 4060452us : __switch_to: prev: alsa-utils <-> next: udevd
[ 3.816977] alsa-uti-989 0d..2 4060452us : __switch_to: set ->fpregs_active
[ 3.816977] udevd-840 0d..2 4060521us : __switch_to: prev: udevd <-> next: udevd
[ 3.816977] udevd-840 0d..2 4060522us : __switch_to: set ->fpregs_active
[ 3.816977] udevd-829 0d..2 4060557us : __switch_to: prev: udevd <-> next: udevd
[ 3.816977] udevd-829 0d..2 4060558us : __switch_to: set ->fpregs_active
[ 3.816977] udevd-840 0d..2 4060862us : __switch_to: prev: udevd <-> next: blkid
[ 3.816977] udevd-840 0d..2 4060862us : __switch_to: set ->fpregs_active
[ 3.816977] blkid-985 0d..2 4061148us : __switch_to: prev: blkid <-> next: udevadm
[ 3.816977] blkid-985 0d..2 4061148us : __switch_to: set ->fpregs_active
Now we're switching back to udevadm which is @next_p of __switch_to().
There we do:
fpu_switch = switch_fpu_prepare(prev_fpu, next_fpu, cpu);
which does:
/* Don't change CR0.TS if we just switch! */
if (fpu.preload) {
new_fpu->counter++;
__fpregs_activate(new_fpu);
prefetch(&new_fpu->state);
__fpregs_activate() sets ->fpregs_active of @new_fpu, i.e. udevadm's one.
[ 3.816977] udevadm-982 0.... 4061149us : __fpu__restore_sig: after schedule: fpregs_active: 1 f443d7c0
__fpu__restore_sig() -> fpu__restore() sets ->fpregs_active again.
[ 3.816977] udevadm-982 0.N.1 4185386us : fpu__restore: WARN: fpu: f443d7c0
Boom!
[ 3.816977] udevadm-982 0.N.1 4185392us : <stack trace>
[ 3.816977] => fpu__restore
[ 3.816977] => __fpu__restore_sig
[ 3.816977] => fpu__restore_sig
[ 3.816977] => restore_sigcontext
[ 3.816977] => sys_sigreturn
[ 3.816977] => do_syscall_32_irqs_on
[ 3.816977] => restore_all
[ 3.816977] ---------------------------------
[ 3.816977] Kernel Offset: disabled
[ 3.816977] ---[ end Kernel panic - not syncing: Outta here...
So yeah, we probably should enlarge the preemption-off region to contain
->fpstate_active. Here's what you basically suggested but with a
*looot* of explanatory text. Which might be really wrong or completely
unparseable or both. So holler what should be changed.
Thanks!
---
From: Borislav Petkov <bp@suse.de>
Date: Mon, 15 Feb 2016 19:50:33 +0100
Subject: [RFC PATCH] x86/FPU: Fix double FPU regs activation
On the entry_INT80_32->do_syscall_32_irqs_on path on 32-bit we run with
interrupts enabled. And it can happen that we get preempted right after
setting ->fpstate_active in a task's FPU.
After we get preempted, we switch between tasks merrily and eventually
are about to switch to that task above whose ->fpstate_active we
set. We enter __switch_to() and do switch_fpu_prepare(). Our task gets
->fpregs_active set, we find ourselves back on the call stack below and
especially in __fpu__restore_sig() which sets ->fpregs_active again.
Leading to that whoops below.
So let's enlarge the preemption-off region so that we set ->fpstate_active with
preemption disabled and thus not trigger fpu.preload:
switch_fpu_prepare
...
fpu.preload = static_cpu_has(X86_FEATURE_FPU) &&
new_fpu->fpstate_active &&
^^^^^^^^^^^^^^^^^^^^^^
prematurely.
WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
Modules linked in: hid_generic usbhid hid snd_hda_codec_hdmi
snd_hda_codec_realtek snd_hda_codec_generic iTCO_wdt iTCO_vendor_support
emp_thermal coretemp kvm_intel kvm irqbypass crc32_pclmul crc32c_intel
iwldvm mac80211 aesni_intel xts snd_hda_intel input_leds aes_i586
sdhci_pci lrw iwlwifi snd_hwdep gf128mul snd_hda_core ablk_helper cryptd
ehci_pci pcspkr serio_raw xhci_pci sdhci snd_pcm sg mmc_core 211 lpc_ich
mfd_core e1000e snd_timer ehci_hcd xhci_hcd thinkpad_acpi nvram wmi snd
battery soundcore led_class ac thermal
CPU: 0 PID: 3031 Comm: bash Not tainted 4.5.0-rc3+ #1
Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012
00000000 00000286 f158be4c c12cce56 00000000 00000000 f158be80 c10567fb
c1866c2c 00000000 00000bd7 c1859e8c 00000212 c1025ab0 00000212 c1025ab0
f2012b00 f2011f00 f2012d80 f158be90 c10568d2 00000009 00000000 f158bea4
Call Trace:
dump_stack
warn_slowpath_common
? fpu__restore
? fpu__restore
warn_slowpath_null
fpu__restore
__fpu__restore_sig
fpu__restore_sig
restore_sigcontext
sys_sigreturn
do_syscall_32_irqs_on
entry_INT80_32
Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/fpu/signal.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 31c6a60505e6..408e5a1c6fdd 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -316,12 +316,11 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
}
+ preempt_disable();
fpu->fpstate_active = 1;
- if (use_eager_fpu()) {
- preempt_disable();
+ if (use_eager_fpu())
fpu__restore(fpu);
- preempt_enable();
- }
+ preempt_enable();
return err;
} else {
--
2.3.5
Tracing patch:
---
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index a2124343edf5..2cbc3bf34928 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -527,9 +527,16 @@ static inline void __fpregs_deactivate(struct fpu *fpu)
/* Must be paired with a 'clts' (fpregs_activate_hw()) before! */
static inline void __fpregs_activate(struct fpu *fpu)
{
- WARN_ON_FPU(fpu->fpregs_active);
+ if (WARN_ON_FPU(fpu->fpregs_active)) {
+ trace_printk("WARN: fpu: %p\n", fpu);
+ trace_dump_stack(0);
+ tracing_off();
+ panic("Outta here...\n");
+ }
fpu->fpregs_active = 1;
+ trace_printk("set ->fpregs_active\n");
+
this_cpu_write(fpu_fpregs_owner_ctx, fpu);
}
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 31c6a60505e6..bb40f02cdfdd 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -317,6 +317,14 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
}
fpu->fpstate_active = 1;
+
+ trace_printk("fpregs_active %d, %p\n", fpu->fpregs_active, fpu);
+
+ schedule();
+
+ trace_printk("after schedule: fpregs_active: %d %p\n",
+ fpu->fpregs_active, fpu);
+
if (use_eager_fpu()) {
preempt_disable();
fpu__restore(fpu);
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 9f950917528b..ce768c728f38 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -249,6 +249,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
struct tss_struct *tss = &per_cpu(cpu_tss, cpu);
fpu_switch_t fpu_switch;
+ trace_printk("prev: %s <-> next: %s\n", prev_p->comm, next_p->comm);
+
/* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
fpu_switch = switch_fpu_prepare(prev_fpu, next_fpu, cpu);
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply related [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-15 19:14 ` Borislav Petkov
@ 2016-02-16 2:25 ` Andy Lutomirski
2016-02-17 8:16 ` Ingo Molnar
0 siblings, 1 reply; 15+ messages in thread
From: Andy Lutomirski @ 2016-02-16 2:25 UTC (permalink / raw)
To: Borislav Petkov; +Cc: linux-kernel, X86 ML
On Feb 15, 2016 12:14 PM, "Borislav Petkov" <bp@alien8.de> wrote:
>
> ---
> From: Borislav Petkov <bp@suse.de>
> Date: Mon, 15 Feb 2016 19:50:33 +0100
> Subject: [RFC PATCH] x86/FPU: Fix double FPU regs activation
>
> On the entry_INT80_32->do_syscall_32_irqs_on path on 32-bit we run with
> interrupts enabled.
I would change this a little bit.
sys_sigreturn calls fpu__restore_sig with interrupts enabled. When
restoring a 32-bit signal frame, it can happen that...
> And it can happen that we get preempted right after
> setting ->fpstate_active in a task's FPU.
>
> After we get preempted, we switch between tasks merrily and eventually
> are about to switch to that task above whose ->fpstate_active we
> set. We enter __switch_to() and do switch_fpu_prepare(). Our task gets
> ->fpregs_active set, we find ourselves back on the call stack below and
> especially in __fpu__restore_sig() which sets ->fpregs_active again.
>
> Leading to that whoops below.
--Andy
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-16 2:25 ` Andy Lutomirski
@ 2016-02-17 8:16 ` Ingo Molnar
2016-02-17 9:29 ` Borislav Petkov
0 siblings, 1 reply; 15+ messages in thread
From: Ingo Molnar @ 2016-02-17 8:16 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: Borislav Petkov, linux-kernel, X86 ML
* Andy Lutomirski <luto@amacapital.net> wrote:
> On Feb 15, 2016 12:14 PM, "Borislav Petkov" <bp@alien8.de> wrote:
> >
> > ---
> > From: Borislav Petkov <bp@suse.de>
> > Date: Mon, 15 Feb 2016 19:50:33 +0100
> > Subject: [RFC PATCH] x86/FPU: Fix double FPU regs activation
> >
> > On the entry_INT80_32->do_syscall_32_irqs_on path on 32-bit we run with
> > interrupts enabled.
>
> I would change this a little bit.
>
> sys_sigreturn calls fpu__restore_sig with interrupts enabled. When
> restoring a 32-bit signal frame, it can happen that...
>
> > And it can happen that we get preempted right after
> > setting ->fpstate_active in a task's FPU.
> >
> > After we get preempted, we switch between tasks merrily and eventually
> > are about to switch to that task above whose ->fpstate_active we
> > set. We enter __switch_to() and do switch_fpu_prepare(). Our task gets
> > ->fpregs_active set, we find ourselves back on the call stack below and
> > especially in __fpu__restore_sig() which sets ->fpregs_active again.
> >
> > Leading to that whoops below.
So I'm wondering why this started triggering only now. Is this a pre-existing bug
that somehow got triggered via:
58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs
? If yes then we need a plausible theory of how that never triggered on modern
Intel CPUs that had eagerfpu enabled for years.
Or perhaps was it caused by one of the other changes in tip:x86/fpu:
c6ab109f7e0e x86/fpu: Speed up lazy FPU restores slightly
a20d7297045f x86/fpu: Fold fpu_copy() into fpu__copy()
5ed73f40735c x86/fpu: Fix FNSAVE usage in eagerfpu mode
4ecd16ec7059 x86/fpu: Fix math emulation in eager fpu mode
?
Which would make this a recently introduced regression.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-17 8:16 ` Ingo Molnar
@ 2016-02-17 9:29 ` Borislav Petkov
2016-02-17 9:35 ` Ingo Molnar
2016-02-17 17:52 ` Andy Lutomirski
0 siblings, 2 replies; 15+ messages in thread
From: Borislav Petkov @ 2016-02-17 9:29 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Andy Lutomirski, linux-kernel, X86 ML
On Wed, Feb 17, 2016 at 09:16:46AM +0100, Ingo Molnar wrote:
> So I'm wondering why this started triggering only now. Is this a pre-existing bug
> that somehow got triggered via:
>
> 58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs
>
> ?
Well, that's an interesting question. See, the thing is, I triggered
this only *once* by accident and I haven't seen it ever since.
The "reliable" "reproducer" I used to debug this was Andy's suggestion
to stick a schedule() in __fpu__restore_sig().
So the answer to that question is not easy.
BUT(!), regardless, the bug still needs to be fixed because my tracing
here
https://lkml.kernel.org/r/20160215191422.GB32716@pd.tnic
showed that getting preempted after setting
fpu->fpstate_active = 1;
leads to the WARN. Because - and please doublecheck me on that - when
we're in __switch_to() and the task which already has ->fpstate_active
set and it is the next task to which we're going to switch to, when it
enters switch_fpu_prepare(), it does:
fpu.preload = static_cpu_has(X86_FEATURE_FPU) &&
new_fpu->fpstate_active &&
^^^^^^^^^^^^^^^^^^^^^^^
so that fpu.preload is set now.
A bit later in that same function:
/* Don't change CR0.TS if we just switch! */
if (fpu.preload) {
new_fpu->counter++;
__fpregs_activate(new_fpu);
^^^^^^^^^^^^^^^^^
->fpregs_active gets set here and when the task returns to
__fpu__restore_sig(), fpu__restore() sets it again, leading to the WARN.
Mind you, this happens on 32-bit only because there we sigreturn with
irqs enabled. Look at the call trace.
> If yes then we need a plausible theory of how that never triggered on
> modern Intel CPUs that had eagerfpu enabled for years.
AFAICT, it triggers - and the window is very small at that - only on
32-bit. If at all.
> Or perhaps was it caused by one of the other changes in tip:x86/fpu:
>
> c6ab109f7e0e x86/fpu: Speed up lazy FPU restores slightly
> a20d7297045f x86/fpu: Fold fpu_copy() into fpu__copy()
> 5ed73f40735c x86/fpu: Fix FNSAVE usage in eagerfpu mode
> 4ecd16ec7059 x86/fpu: Fix math emulation in eager fpu mode
>
> ?
I can certainly try to test all those but I don't have a reliable
reproducer. The only thing I could do is check out each of those commits
and stick a schedule() in __fpu__restore_sig() and see what happens.
But if my analysis above is right, none of those would matter because of
the mechanism of how the warn happens...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-17 9:29 ` Borislav Petkov
@ 2016-02-17 9:35 ` Ingo Molnar
2016-02-17 10:31 ` Borislav Petkov
2016-02-17 17:52 ` Andy Lutomirski
1 sibling, 1 reply; 15+ messages in thread
From: Ingo Molnar @ 2016-02-17 9:35 UTC (permalink / raw)
To: Borislav Petkov; +Cc: Andy Lutomirski, linux-kernel, X86 ML
* Borislav Petkov <bp@alien8.de> wrote:
> On Wed, Feb 17, 2016 at 09:16:46AM +0100, Ingo Molnar wrote:
> > So I'm wondering why this started triggering only now. Is this a pre-existing bug
> > that somehow got triggered via:
> >
> > 58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs
> >
> > ?
>
> Well, that's an interesting question. See, the thing is, I triggered
> this only *once* by accident and I haven't seen it ever since.
>
> The "reliable" "reproducer" I used to debug this was Andy's suggestion
> to stick a schedule() in __fpu__restore_sig().
>
> So the answer to that question is not easy.
>
> BUT(!), regardless, the bug still needs to be fixed because my tracing
> here
The fix is absolutely needed, I just would like deeper analysis about how it
wasn't seen before.
> > If yes then we need a plausible theory of how that never triggered on modern
> > Intel CPUs that had eagerfpu enabled for years.
>
> AFAICT, it triggers - and the window is very small at that - only on
> 32-bit. If at all.
So it probably triggers on vanilla v4.4 (or v4.5-rc4) as well, with no recent FPU
bits applied?
> I can certainly try to test all those but I don't have a reliable reproducer.
> The only thing I could do is check out each of those commits and stick a
> schedule() in __fpu__restore_sig() and see what happens.
>
> But if my analysis above is right, none of those would matter because of the
> mechanism of how the warn happens...
So if you stick a schedule() into vanilla and it triggers then I think we can
declare it an existing bug. (and then the fix also needs Cc: stable)
Thanks,
Ingo
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-17 9:35 ` Ingo Molnar
@ 2016-02-17 10:31 ` Borislav Petkov
2016-02-17 11:06 ` Ingo Molnar
2016-02-17 11:41 ` Borislav Petkov
0 siblings, 2 replies; 15+ messages in thread
From: Borislav Petkov @ 2016-02-17 10:31 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Andy Lutomirski, linux-kernel, X86 ML
On Wed, Feb 17, 2016 at 10:35:12AM +0100, Ingo Molnar wrote:
> So it probably triggers on vanilla v4.4 (or v4.5-rc4) as well, with no
> recent FPU bits applied?
Nope, 4.4 doesn't trigger. Lemme try some of those other commits...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-17 10:31 ` Borislav Petkov
@ 2016-02-17 11:06 ` Ingo Molnar
2016-02-17 11:41 ` Borislav Petkov
1 sibling, 0 replies; 15+ messages in thread
From: Ingo Molnar @ 2016-02-17 11:06 UTC (permalink / raw)
To: Borislav Petkov; +Cc: Andy Lutomirski, linux-kernel, X86 ML
* Borislav Petkov <bp@alien8.de> wrote:
> On Wed, Feb 17, 2016 at 10:35:12AM +0100, Ingo Molnar wrote:
> > So it probably triggers on vanilla v4.4 (or v4.5-rc4) as well, with no
> > recent FPU bits applied?
>
> Nope, 4.4 doesn't trigger. Lemme try some of those other commits...
My guess is:
58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs
but could be one of the others as well ...
Thanks,
Ingo
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-17 10:31 ` Borislav Petkov
2016-02-17 11:06 ` Ingo Molnar
@ 2016-02-17 11:41 ` Borislav Petkov
1 sibling, 0 replies; 15+ messages in thread
From: Borislav Petkov @ 2016-02-17 11:41 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Andy Lutomirski, linux-kernel, X86 ML
On Wed, Feb 17, 2016 at 11:31:41AM +0100, Borislav Petkov wrote:
> On Wed, Feb 17, 2016 at 10:35:12AM +0100, Ingo Molnar wrote:
> > So it probably triggers on vanilla v4.4 (or v4.5-rc4) as well, with no
> > recent FPU bits applied?
>
> Nope, 4.4 doesn't trigger. Lemme try some of those other commits...
Results:
tip/x86/fpu:
58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs - BAD
c6ab109f7e0e x86/fpu: Speed up lazy FPU restores slightly - BAD
a20d7297045f x86/fpu: Fold fpu_copy() into fpu__copy() - BAD
5ed73f40735c x86/fpu: Fix FNSAVE usage in eagerfpu mode - BAD
4ecd16ec7059 x86/fpu: Fix math emulation in eager fpu mode - BAD
765bdb406de4 ("Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm") - BAD
...
v4.4: GOOD
so it must be something else causing it AFAICT.
I'll continue trying the -rc's and the tip/master merges to see what
causes it. Let me know if you have a better idea.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130()
2016-02-17 9:29 ` Borislav Petkov
2016-02-17 9:35 ` Ingo Molnar
@ 2016-02-17 17:52 ` Andy Lutomirski
1 sibling, 0 replies; 15+ messages in thread
From: Andy Lutomirski @ 2016-02-17 17:52 UTC (permalink / raw)
To: Borislav Petkov; +Cc: X86 ML, linux-kernel, Ingo Molnar
On Feb 17, 2016 1:29 AM, "Borislav Petkov" <bp@alien8.de> wrote:
>
> On Wed, Feb 17, 2016 at 09:16:46AM +0100, Ingo Molnar wrote:
> > So I'm wondering why this started triggering only now. Is this a pre-existing bug
> > that somehow got triggered via:
> >
> > 58122bf1d856 x86/fpu: Default eagerfpu=on on all CPUs
> >
> > ?
>
> Well, that's an interesting question. See, the thing is, I triggered
> this only *once* by accident and I haven't seen it ever since.
>
> The "reliable" "reproducer" I used to debug this was Andy's suggestion
> to stick a schedule() in __fpu__restore_sig().
>
> So the answer to that question is not easy.
>
> BUT(!), regardless, the bug still needs to be fixed because my tracing
> here
>
> https://lkml.kernel.org/r/20160215191422.GB32716@pd.tnic
>
> showed that getting preempted after setting
>
> fpu->fpstate_active = 1;
>
> leads to the WARN. Because - and please doublecheck me on that - when
> we're in __switch_to() and the task which already has ->fpstate_active
> set and it is the next task to which we're going to switch to, when it
> enters switch_fpu_prepare(), it does:
>
> fpu.preload = static_cpu_has(X86_FEATURE_FPU) &&
> new_fpu->fpstate_active &&
> ^^^^^^^^^^^^^^^^^^^^^^^
>
> so that fpu.preload is set now.
>
> A bit later in that same function:
>
> /* Don't change CR0.TS if we just switch! */
> if (fpu.preload) {
> new_fpu->counter++;
> __fpregs_activate(new_fpu);
> ^^^^^^^^^^^^^^^^^
>
> ->fpregs_active gets set here and when the task returns to
> __fpu__restore_sig(), fpu__restore() sets it again, leading to the WARN.
>
> Mind you, this happens on 32-bit only because there we sigreturn with
> irqs enabled. Look at the call trace.
Not quite. IRQs are on in the 64-bit case, too, but the problematic
code doesn't run because the 64-bit sigreturn case doesn't need to
fiddle with the fpu layout.
--Andy
^ permalink raw reply [flat|nested] 15+ messages in thread
end of thread, other threads:[~2016-02-17 17:53 UTC | newest]
Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
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2016-02-11 19:27 WARNING: CPU: 0 PID: 3031 at ./arch/x86/include/asm/fpu/internal.h:530 fpu__restore+0x90/0x130() Borislav Petkov
2016-02-11 23:47 ` Andy Lutomirski
2016-02-12 1:16 ` Andy Lutomirski
2016-02-12 17:00 ` Borislav Petkov
2016-02-15 19:14 ` Borislav Petkov
2016-02-16 2:25 ` Andy Lutomirski
2016-02-17 8:16 ` Ingo Molnar
2016-02-17 9:29 ` Borislav Petkov
2016-02-17 9:35 ` Ingo Molnar
2016-02-17 10:31 ` Borislav Petkov
2016-02-17 11:06 ` Ingo Molnar
2016-02-17 11:41 ` Borislav Petkov
2016-02-17 17:52 ` Andy Lutomirski
2016-02-15 19:05 ` Borislav Petkov
2016-02-12 11:17 ` Borislav Petkov
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