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[PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access

From Andy Lutomirski <luto@kernel.org>
Newsgroups linux.kernel
Subject [PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access
Date 2015-10-06 03:00 +0200
Message-ID <qgoLN-7cw-31@gated-at.bofh.it> (permalink)
References <qgoC6-715-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Clearing NT is part of the prologue, whereas loading up arg6 makes
more sense to think about as part of syscall processing.  Reorder
them.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/entry_64_compat.S | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index a9360d40fb7f..aa76864a8a6b 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -89,15 +89,6 @@ ENTRY(entry_SYSENTER_compat)
 	sub	$(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */
 
 	/*
-	 * no need to do an access_ok check here because rbp has been
-	 * 32-bit zero extended
-	 */
-	ASM_STAC
-1:	movl	(%rbp), %ebp
-	_ASM_EXTABLE(1b, ia32_badarg)
-	ASM_CLAC
-
-	/*
 	 * Sysenter doesn't filter flags, so we need to clear NT
 	 * ourselves.  To save a few cycles, we can check whether
 	 * NT was set instead of doing an unconditional popfq.
@@ -106,6 +97,15 @@ ENTRY(entry_SYSENTER_compat)
 	jnz	sysenter_fix_flags
 sysenter_flags_fixed:
 
+	/*
+	 * no need to do an access_ok check here because rbp has been
+	 * 32-bit zero extended
+	 */
+	ASM_STAC
+1:	movl	(%rbp), %ebp
+	_ASM_EXTABLE(1b, ia32_badarg)
+	ASM_CLAC
+
 	orl	$TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
 	testl	$_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
 	jnz	sysenter_tracesys
-- 
2.4.3

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Thread

[PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access Andy Lutomirski <luto@kernel.org> - 2015-10-06 03:00 +0200
  Re: [PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag  before user memory access Borislav Petkov <bp@alien8.de> - 2015-10-07 13:20 +0200
    Re: [PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag  before user memory access Brian Gerst <brgerst@gmail.com> - 2015-10-07 16:40 +0200
      Re: [PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag  before user memory access Borislav Petkov <bp@alien8.de> - 2015-10-07 17:10 +0200
        [PATCH] x86/entry/64/compat: Document sysenter_fix_flags's reason  for existence Borislav Petkov <bp@alien8.de> - 2015-10-09 19:10 +0200
          Re: [PATCH] x86/entry/64/compat: Document sysenter_fix_flags's reason  for existence Andy Lutomirski <luto@amacapital.net> - 2015-10-09 21:10 +0200
          [tip:x86/asm] x86/entry/64/compat: Document sysenter_fix_flags'  s reason for existence tip-bot for Borislav Petkov <tipbot@zytor.com> - 2015-10-11 11:20 +0200
  [tip:x86/asm] x86/entry/64/compat: Fix SYSENTER'  s NT flag before user memory access tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2015-10-07 18:20 +0200

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