linux-kernel - Re: Sanitize CPU-state when switching tasks (was sanitize CPU-state when switching from virtual-8086 mode to other task)

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Date:	Fri, 10 Jan 2014 00:02:10 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	halfdog <me@...fdog.net>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Ben Hutchings <ben@...adent.org.uk>
Subject: Re: Sanitize CPU-state when switching tasks (was sanitize CPU-state
 when switching from virtual-8086 mode to other task)

On Thu, Jan 09, 2014 at 10:50:28PM +0000, halfdog wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> It took me some time to build me the Debian Sid testing environment
> for amd64 with the same quality, I have vor i386, but now it is ready.
> And it seems, that amd64 is also affected, but lockup is immediately
> (makes exploitation harder)
> 
> Here is the OOPS from the serial console, again in __switch_to
> 
> [  498.783577] fpu exception: 0000 [#1] SMP
> [  498.787054] Modules linked in: xt_multiport xt_hashlimit xt_tcpudp
> ipt_ULOG xt_LOG xt_conntrack iptable_raw iptable_nat nf_conntrack_ipv4
> nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
> iptable_filter ip_tables x_tables fuse snd_pcm snd_page_alloc
> snd_timer snd soundcore i2c_piix4 psmouse pcspkr evdev serio_raw
> i2c_core parport_pc parport battery button ac ext4 crc16 mbcache jbd2
> sd_mod crc_t10dif crct10dif_common sg sr_mod cdrom ata_generic
> virtio_net mptspi scsi_transport_spi ata_piix virtio_pci virtio_ring
> virtio mptscsih mptbase libata scsi_mod
> [  498.787205] CPU: 0 PID: 1783 Comm: Test Not tainted 3.12-1-amd64 #1
> Debian 3.12.6-2
> [  498.787205] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS
> VirtualBox 12/01/2006
> [  498.787205] task: ffff88000cb18840 ti: ffff88000b454000 task.ti:
> ffff88000b454000
> [  498.787205] RIP: 0010:[<ffffffff81011730>]  [<ffffffff81011730>]
> __switch_to+0x2d0/0x490
> [  498.787205] RSP: 0018:ffff88000e0c78b8  EFLAGS: 00010002
> [  498.787205] RAX: 0000000000000001 RBX: ffff88000e0b77c0 RCX:
> 00000000c0000100
> [  498.787205] RDX: 0000000000000000 RSI: 0000000051e3f800 RDI:
> 00000000c0000100
> [  498.787205] RBP: ffff88000cb18840 R08: 0000000000000000 R09:
> 0000000000003314
> [  498.787205] R10: 0000000000001746 R11: 000000000000000f R12:
> 0000000000000000
> [  498.787205] R13: 0000000000000000 R14: ffff88000fc11780 R15:
> 0000000000000000
> [  498.787205] FS:  00007fb651e3f800(0000) GS:ffff88000fc00000(0000)
> knlGS:0000000000000000
> [  498.787205] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  498.787205] CR2: 00007f72ddfcc990 CR3: 000000000e22d000 CR4:
> 00000000000006f0
> [  498.787205] Stack:
> [  498.787205]  ffff88000e0b7bc0 000000010fc14330 ffff88000b4efac0
> ffff88000e0b77c0
> [  498.787205]  ffff88000fc142c0 ffff88000b5d3b40 0000000000000000
> ffff88000e0b77c0
> [  498.787205]  ffffffff8148febe ffff88000e0b77c0 0000000000000086
> 00000000000142c0
> [  498.787205] Call Trace:
> [  498.787205] Code: ff 66 2e 0f 1f 84 00 00 00 00 00 bf 7d 00 00 00
> e8 e6 00 01 00 84 c0 0f 85 d7 fd ff ff 0f 06 66 66 90 66 90 e9 cb fd
> ff ff 66 90 <0f> 77 db 83 94 04 00 00 66 90 eb 74 b8 ff ff ff ff 48 8b

Yep, EMMS again: 0f 77 - unhandled x87 FPU exception, see my other mail
I just sent.

I'll try this on another AMD machine tomorrow to see whether it is
affected too.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--
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