Re: [ 027/102] x86, vm86: fix VM86 syscalls: use SYSCALL_DEFINEx(...)

[Satoru Takeuchi <satoru.takeuchi@gmail.com>]

At Sun, 19 May 2013 11:37:27 -0700,
Greg Kroah-Hartman wrote:
> 
> On Fri, May 17, 2013 at 04:51:33PM -0700, Greg Kroah-Hartman wrote:
> > On Fri, May 17, 2013 at 11:49:30PM +0100, Al Viro wrote:
> > > On Fri, May 17, 2013 at 02:35:42PM -0700, Greg Kroah-Hartman wrote:
> > > > 3.9-stable review patch.  If anyone has any objections, please let me know.
> > > 
> > > This is seriously wrong.  For 3.9 you _need_ asmlinkage_protect() in that
> > > thing; by the time when that went into the tree, mainline already had
> > > it generated automatically by SYSCALL_DEFINE, so there was no point in
> > > that part of patch - the switch to SYSCALL_DEFINE alone did the job.
> > > For 3.9 it's very much needed; as the matter of fact, in 3.9 that commit
> > > is a no-op in the form you took.
> > > 
> > > We can grab all prereqs into 3.9-stable (there's not that much of those),
> > > but that would be much more intrusive than the variant adding explicit
> > > asmlinkage_protect() in those two syscalls.
> > 
> > Ok, Alexander was saying something was off here.
> > 
> > Can someone send me just the needed patch to get this working properly,
> > and I will be glad to drop this one from the 3.9.x tree.
> 
> I've now dropped this, and will release without it.

Here is the backported patch. It calls asmlinkage_protect() properly and is
as similar to upstream patch as possible.

It can be applied to 3.9.3 and can be built successfully.

Satoru

---
From: Satoru Takeuchi <satoru.takeuchi@gmail.com>
Date: Mon, 20 May 2013 21:32:20 +0900
Subject: x86, vm86: fix VM86 syscalls: use SYSCALL_DEFINEx(...)

commit 5522ddb3fc0dfd4a503c8278eafd88c9f2d3fada upstream.

Commit 49cb25e9290 x86: 'get rid of pt_regs argument in vm86/vm86old'
got rid of the pt_regs stub for sys_vm86old and sys_vm86. The functions
were, however, not changed to use the calling convention for syscalls.

Reported-and-tested-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/syscalls.h |    4 ++--
 arch/x86/kernel/vm86_32.c       |   11 ++++++-----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
index 6cf0a9c..5a0be0a 100644
--- a/arch/x86/include/asm/syscalls.h
+++ b/arch/x86/include/asm/syscalls.h
@@ -37,8 +37,8 @@ asmlinkage int sys_get_thread_area(struct user_desc __user *);
 unsigned long sys_sigreturn(void);
 
 /* kernel/vm86_32.c */
-int sys_vm86old(struct vm86_struct __user *);
-int sys_vm86(unsigned long, unsigned long);
+asmlinkage long sys_vm86old(struct vm86_struct __user *);
+asmlinkage long sys_vm86(unsigned long, unsigned long);
 
 #else /* CONFIG_X86_32 */
 
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 1cf5766..3dbdd9c 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -33,6 +33,7 @@
 #include <linux/capability.h>
 #include <linux/errno.h>
 #include <linux/interrupt.h>
+#include <linux/syscalls.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/signal.h>
@@ -48,7 +49,6 @@
 #include <asm/io.h>
 #include <asm/tlbflush.h>
 #include <asm/irq.h>
-#include <asm/syscalls.h>
 
 /*
  * Known problems:
@@ -202,17 +202,16 @@ out:
 static int do_vm86_irq_handling(int subfunction, int irqnumber);
 static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk);
 
-int sys_vm86old(struct vm86_struct __user *v86)
+SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, v86)
 {
 	struct kernel_vm86_struct info; /* declare this _on top_,
 					 * this avoids wasting of stack space.
 					 * This remains on the stack until we
 					 * return to 32 bit user space.
 					 */
-	struct task_struct *tsk;
+	struct task_struct *tsk = current;
 	int tmp, ret = -EPERM;
 
-	tsk = current;
 	if (tsk->thread.saved_sp0)
 		goto out;
 	tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
@@ -227,11 +226,12 @@ int sys_vm86old(struct vm86_struct __user *v86)
 	do_sys_vm86(&info, tsk);
 	ret = 0;	/* we never return here */
 out:
+	asmlinkage_protect(1, ret, v86);
 	return ret;
 }
 
 
-int sys_vm86(unsigned long cmd, unsigned long arg)
+SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
 {
 	struct kernel_vm86_struct info; /* declare this _on top_,
 					 * this avoids wasting of stack space.
@@ -278,6 +278,7 @@ int sys_vm86(unsigned long cmd, unsigned long arg)
 	do_sys_vm86(&info, tsk);
 	ret = 0;	/* we never return here */
 out:
+	asmlinkage_protect(2, ret, cmd, arg);
 	return ret;
 }
 
-- 
1.7.10.4