[tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES area

From	tip-bot for Kevin Hao <tipbot@zytor.com>
Newsgroups	linux.kernel
Subject	[tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES area
Date	2017-01-23 10:50 +0100
Message-ID	<t2Jqa-4Km-31@gated-at.bofh.it> (permalink)
References	<t2mae-73t-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Commit-ID:  4c833368f0bf748d4147bf301b1f95bc8eccb3c0
Gitweb:     http://git.kernel.org/tip/4c833368f0bf748d4147bf301b1f95bc8eccb3c0
Author:     Kevin Hao <haokexin@gmail.com>
AuthorDate: Sun, 22 Jan 2017 16:50:23 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 23 Jan 2017 10:40:18 +0100

x86/fpu: Set the xcomp_bv when we fake up a XSAVES area

I got the following calltrace on a Apollo Lake SoC with 32-bit kernel:

  WARNING: CPU: 2 PID: 261 at arch/x86/include/asm/fpu/internal.h:363 fpu__restore+0x1f5/0x260
  [...]
  Hardware name: Intel Corp. Broxton P/NOTEBOOK, BIOS APLIRVPA.X64.0138.B35.1608091058 08/09/2016
  Call Trace:
   dump_stack()
   __warn()
   ? fpu__restore()
   warn_slowpath_null()
   fpu__restore()
   __fpu__restore_sig()
   fpu__restore_sig()
   restore_sigcontext.isra.9()
   sys_sigreturn()
   do_int80_syscall_32()
   entry_INT80_32()

The reason is that a #GP occurs when executing XRSTORS. The root cause
is that we forget to set the xcomp_bv when we fake up the XSAVES area
in the copyin_to_xsaves() function.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/1485075023-30161-1-git-send-email-haokexin@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/fpu/xstate.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 1d77704..e287b90 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1070,6 +1070,7 @@ int copyin_to_xsaves(const void *kbuf, const void __user *ubuf,
 	 * Add back in the features that came in from userspace:
 	 */
 	xsave->header.xfeatures |= xfeatures;
+	xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xsave->header.xfeatures;
 
 	return 0;
 }

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[PATCH] x86/fpu: set the xcomp_bv when we fake up a XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-22 10:00 +0100
  [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES  area tip-bot for Kevin Hao <tipbot@zytor.com> - 2017-01-23 09:30 +0100
    Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 16:40 +0100
      Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-01-23 18:00 +0100
        Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 18:30 +0100
          Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-01-23 22:10 +0100
            Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 22:20 +0100
              Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-01-23 22:30 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-23 22:30 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 01:20 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-24 02:00 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 03:00 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-24 03:10 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 03:20 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Dave Hansen <dave.hansen@linux.intel.com> - 2017-01-24 03:40 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Kevin Hao <haokexin@gmail.com> - 2017-01-24 06:20 +0100
                Re: [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a  XSAVES area Ingo Molnar <mingo@kernel.org> - 2017-01-24 09:10 +0100
  [tip:x86/urgent] x86/fpu: Set the xcomp_bv when we fake up a XSAVES  area tip-bot for Kevin Hao <tipbot@zytor.com> - 2017-01-23 10:50 +0100

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