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[PATCH 3.13.y-ckt 08/78] x86/fpu: Fix 32-bit signal frame handling

From Kamal Mostafa <kamal@canonical.com>
Newsgroups linux.kernel
Subject [PATCH 3.13.y-ckt 08/78] x86/fpu: Fix 32-bit signal frame handling
Date 2015-12-17 01:50 +0100
Message-ID <qGuVD-Ae-83@gated-at.bofh.it> (permalink)
References <qGuVA-Ae-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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3.13.11-ckt32 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Hansen <dave.hansen@linux.intel.com>

commit ab6b52947545a5355154f64f449f97af9d05845f upstream.

(This should have gone to LKML originally. Sorry for the extra
 noise, folks on the cc.)

Background:

Signal frames on x86 have two formats:

  1. For 32-bit executables (whether on a real 32-bit kernel or
     under 32-bit emulation on a 64-bit kernel) we have a
    'fpregset_t' that includes the "FSAVE" registers.

  2. For 64-bit executables (on 64-bit kernels obviously), the
     'fpregset_t' is smaller and does not contain the "FSAVE"
     state.

When creating the signal frame, we have to be aware of whether
we are running a 32 or 64-bit executable so we create the
correct format signal frame.

Problem:

save_xstate_epilog() uses 'fx_sw_reserved_ia32' whenever it is
called for a 32-bit executable.  This is for real 32-bit and
ia32 emulation.

But, fpu__init_prepare_fx_sw_frame() only initializes
'fx_sw_reserved_ia32' when emulation is enabled, *NOT* for real
32-bit kernels.

This leads to really wierd situations where 32-bit programs
lose their extended state when returning from a signal handler.
The kernel copies the uninitialized (zero) 'fx_sw_reserved_ia32'
out to userspace in save_xstate_epilog().  But when returning
from the signal, the kernel errors out in check_for_xstate()
when it does not see FP_XSTATE_MAGIC1 present (because it was
zeroed).  This leads to the FPU/XSAVE state being initialized.

For MPX, this leads to the most permissive state and means we
silently lose bounds violations.  I think this would also mean
that we could lose *ANY* FPU/SSE/AVX state.  I'm not sure why
no one has spotted this bug.

I believe this was broken by:

	72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")

way back in 2012.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@sr71.net
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
Link: http://lkml.kernel.org/r/20151111002354.A0799571@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[ luis: backported to 3.16:
  - file and function rename:
    * arch/x86/kernel/fpu/signal.c -> arch/x86/kernel/xsave.c
    * fpu__init_prepare_fx_sw_frame() -> prepare_fx_sw_frame()
  - use 'i387_fsave_struct' instead of 'fregs_state'
  - adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 arch/x86/kernel/xsave.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index bf640b8..cf2e969 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -429,20 +429,19 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
  */
 static void prepare_fx_sw_frame(void)
 {
-	int fsave_header_size = sizeof(struct i387_fsave_struct);
 	int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;
 
-	if (config_enabled(CONFIG_X86_32))
-		size += fsave_header_size;
-
 	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
 	fx_sw_reserved.extended_size = size;
 	fx_sw_reserved.xstate_bv = pcntxt_mask;
 	fx_sw_reserved.xstate_size = xstate_size;
 
-	if (config_enabled(CONFIG_IA32_EMULATION)) {
+	if (config_enabled(CONFIG_IA32_EMULATION) ||
+	    config_enabled(CONFIG_X86_32)) {
+		int fsave_header_size = sizeof(struct i387_fsave_struct);
+
 		fx_sw_reserved_ia32 = fx_sw_reserved;
-		fx_sw_reserved_ia32.extended_size += fsave_header_size;
+		fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
 	}
 }
 
-- 
1.9.1

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[3.13.y-ckt stable] Linux 3.13.11-ckt32 stable review Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 38/78] vfs: Make sendfile(2) killable even better Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 56/78] sched/core: Clear the root_domain cpumasks in init_rootdomain() Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 72/78] packet: only allow extra vlan len on ethernet devices Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 62/78] tcp: md5: fix lockdep annotation Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 63/78] ARM: dts: Kirkwood: Fix QNAP TS219 power-off Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 47/78] drm/radeon: make some dpm errors debug only Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 04/78] iio: lpc32xx_adc: fix warnings caused by enabling unprepared clock Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 27/78] USB: option: add XS Stick W100-2 from 4G Systems Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 68/78] net: mvneta: fix bit assignment for RX packet irq enable Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 75/78] net: ip6mr: fix static mfc/dev leaks on table destruction Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 08/78] x86/fpu: Fix 32-bit signal frame handling Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 64/78] isdn: Partially revert debug format string usage clean up Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 65/78] remoteproc: avoid stack overflow in debugfs file Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 76/78] unix: avoid use-after-free in ep_remove_wait_queue Kamal Mostafa <kamal@canonical.com> - 2015-12-17 01:50 +0100
  [PATCH 3.13.y-ckt 35/78] powerpc/tm: Block signal return setting invalid MSR state Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 58/78] mmc: remove bondage between REQ_META and reliable write Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 55/78] wan/x25: Fix use-after-free in x25_asy_open_tty() Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 45/78] RDS: fix race condition when sending a message on unbound socket Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 46/78] btrfs: fix signed overflows in btrfs_sync_file Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 37/78] fix sysvfs symlinks Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 51/78] target: Fix race for SCF_COMPARE_AND_WRITE_POST checking Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 48/78] nfs: if we have no valid attrs, then don't declare the attribute cache valid Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 49/78] xen/gntdev: Grant maps should not be subject to NUMA balancing Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 54/78] Fix a memory leak in scsi_host_dev_release() Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 57/78] x86/signal: Fix restart_syscall number for x32 tasks Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 43/78] arm64: KVM: Fix AArch32 to AArch64 register mapping Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 50/78] iscsi-target: Fix rx_login_comp hang after login failure Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 60/78] usb: musb: core: fix order of arguments to ulpi write callback Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 53/78] block: Always check queue limits for cloned requests Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 03/78] stackprotector: Introduce CONFIG_CC_STACKPROTECTOR_STRONG Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 59/78] sctp: translate host order to network order when setting a hmacid Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 52/78] target: fix COMPARE_AND_WRITE non zero SGL offset data corruption Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:00 +0100
  [PATCH 3.13.y-ckt 36/78] ARC: dw2 unwind: Remove falllback linear search thru FDE entries Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 31/78] fat: fix fake_offset handling on error path Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 42/78] ring-buffer: Update read stamp with first real commit on page Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 15/78] mac80211: mesh: fix call_rcu() usage Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 44/78] drm/radeon: make rv770_set_sw_state failures non-fatal Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 30/78] ALSA: hda - Apply HP headphone fixups more generically Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 33/78] parisc: Drop unused MADV_xxxK_PAGES flags from asm/mman.h Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 19/78] MIPS: KVM: Fix ASID restoration logic Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 23/78] xhci: Fix a race in usb2 LPM resume, blocking U3 for usb2 devices Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 32/78] kernel/signal.c: unexport sigsuspend() Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 21/78] MIPS: KVM: Uninit VCPU in vcpu_create error path Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 12/78] USB: serial: option: add support for Novatel MiFi USB620L Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 22/78] xhci: Workaround to get Intel xHCI reset working more reliably Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 16/78] usb: dwc3: gadget: let us set lower max_speed Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 40/78] nfs4: start callback_ident at idr 1 Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 14/78] ASoC: wm8962: correct addresses for HPF_C_0/1 Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 41/78] ALSA: hda - Fix headphone noise after Dell XPS 13 resume back from S3 Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 13/78] USB: ti_usb_3410_5052: Add Honeywell HGI80 ID Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 28/78] usblp: do not set TASK_INTERRUPTIBLE before lock Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 20/78] MIPS: KVM: Fix CACHE immediate offset sign extension Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 39/78] vfs: Avoid softlockups with sendfile(2) Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 25/78] ALSA: hda - Add fixup for Acer Aspire One Cloudbook 14 Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 29/78] mac: validate mac_partition is within sector Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 24/78] x86/cpu: Fix SMAP check in PVOPS environments Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 26/78] arm64: restore bogomips information in /proc/cpuinfo Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:10 +0100
  [PATCH 3.13.y-ckt 05/78] iio:ad5064: Make sure ad5064_i2c_write() returns 0 on success Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100
  [PATCH 3.13.y-ckt 10/78] ALSA: usb-audio: prevent CH345 multiport output SysEx corruption Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100
  [PATCH 3.13.y-ckt 11/78] ALSA: usb-audio: work around CH345 input SysEx corruption Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100
  [PATCH 3.13.y-ckt 07/78] iio:ad7793: Fix ad7785 product ID Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100
  [PATCH 3.13.y-ckt 01/78] tty: fix stall caused by missing memory barrier in drivers/tty/n_tty.c Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100
  [PATCH 3.13.y-ckt 09/78] ALSA: usb-audio: add packet size quirk for the Medeli DD305 Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100
  [PATCH 3.13.y-ckt 06/78] iio: ad5064: Fix ad5629/ad5669 shift Kamal Mostafa <kamal@canonical.com> - 2015-12-17 02:20 +0100

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