linux-kernel - [PATCH 4.17 216/220] x86/entry/64/compat: Fix "x86/entry/64/compat: Preserve r8-r11 in int $0x80"

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Date:   Sun,  1 Jul 2018 18:24:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, zhijianx.li@...el.com,
        Andy Lutomirski <luto@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.17 216/220] x86/entry/64/compat: Fix "x86/entry/64/compat: Preserve r8-r11 in int $0x80"

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

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

From: Andy Lutomirski <luto@...nel.org>

commit 22cd978e598618e82c3c3348d2069184f6884182 upstream.

Commit:

  8bb2610bc496 ("x86/entry/64/compat: Preserve r8-r11 in int $0x80")

was busted: my original patch had a minor conflict with
some of the nospec changes, but "git apply" is very clever
and silently accepted the patch by making the same changes
to a different function in the same file.  There was obviously
a huge offset, but "git apply" for some reason doesn't feel
any need to say so.

Move the changes to the correct function.  Now the
test_syscall_vdso_32 selftests passes.

If anyone cares to observe the original problem, try applying the
patch at:

  https://lore.kernel.org/lkml/d4c4d9985fbe64f8c9e19291886453914b48caee.1523975710.git.luto@kernel.org/raw

to the kernel at 316d097c4cd4e7f2ef50c40cff2db266593c4ec4:

 - "git am" and "git apply" accept the patch without any complaints at all
 - "patch -p1" at least prints out a message about the huge offset.

Reported-by: zhijianx.li@...el.com
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org #v4.17+
Fixes: 8bb2610bc496 ("x86/entry/64/compat: Preserve r8-r11 in int $0x80")
Link: http://lkml.kernel.org/r/6012b922485401bc42676e804171ded262fc2ef2.1530078306.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/entry/entry_64_compat.S |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -84,13 +84,13 @@ ENTRY(entry_SYSENTER_compat)
 	pushq	%rdx			/* pt_regs->dx */
 	pushq	%rcx			/* pt_regs->cx */
 	pushq	$-ENOSYS		/* pt_regs->ax */
-	pushq   %r8			/* pt_regs->r8 */
+	pushq   $0			/* pt_regs->r8  = 0 */
 	xorl	%r8d, %r8d		/* nospec   r8 */
-	pushq   %r9			/* pt_regs->r9 */
+	pushq   $0			/* pt_regs->r9  = 0 */
 	xorl	%r9d, %r9d		/* nospec   r9 */
-	pushq   %r10			/* pt_regs->r10 */
+	pushq   $0			/* pt_regs->r10 = 0 */
 	xorl	%r10d, %r10d		/* nospec   r10 */
-	pushq   %r11			/* pt_regs->r11 */
+	pushq   $0			/* pt_regs->r11 = 0 */
 	xorl	%r11d, %r11d		/* nospec   r11 */
 	pushq   %rbx                    /* pt_regs->rbx */
 	xorl	%ebx, %ebx		/* nospec   rbx */
@@ -374,13 +374,13 @@ ENTRY(entry_INT80_compat)
 	pushq	%rcx			/* pt_regs->cx */
 	xorl	%ecx, %ecx		/* nospec   cx */
 	pushq	$-ENOSYS		/* pt_regs->ax */
-	pushq   $0			/* pt_regs->r8  = 0 */
+	pushq   %r8			/* pt_regs->r8 */
 	xorl	%r8d, %r8d		/* nospec   r8 */
-	pushq   $0			/* pt_regs->r9  = 0 */
+	pushq   %r9			/* pt_regs->r9 */
 	xorl	%r9d, %r9d		/* nospec   r9 */
-	pushq   $0			/* pt_regs->r10 = 0 */
+	pushq   %r10			/* pt_regs->r10*/
 	xorl	%r10d, %r10d		/* nospec   r10 */
-	pushq   $0			/* pt_regs->r11 = 0 */
+	pushq   %r11			/* pt_regs->r11 */
 	xorl	%r11d, %r11d		/* nospec   r11 */
 	pushq   %rbx                    /* pt_regs->rbx */
 	xorl	%ebx, %ebx		/* nospec   rbx */