[PATCH] check put_user fail in do_signal when enable OABI_COMPACT

[jpihet@mvista.com (Jean Pihet)]

On Tuesday 27 October 2009 20:35:31 Nicolas Pitre wrote:
> On Tue, 27 Oct 2009, Jean Pihet wrote:
> > Nicolas,
> >
> > On Tuesday 27 October 2009 19:59:36 Nicolas Pitre wrote:
> > ...
> >
> > > > Side question: does the put_user requires a flush of some sort? If
> > > > not, why?
> > >
> > > No because it stores data into the d-cache directly at the virtual
> > > address to be used by user space.  Previously the d-cache needed to
> > > be cleaned for data to hit main memory and the i-cache invalidated for
> > > the newly stored _code_ to be seen by the instruction path.  Since
> > > there is no code involved anymore the cache flushes are useless.
> > >
> > > > Is it OK to re-send a patch with the call to flush_icache_range
> > > > removed?
> > >
> > > Yes.
> >
> > Ok here is the updated patch. Let's hope it is the good one that time ;-)
>
> Well, the commit message is certainly wrong. There is no copying of
> restart_syscall to user stack anymore.
Ok thanks for reviewing it! Here is a respin of the patch. Only the commit 
description has been touched.

>
> And is there a reason for touching sp in the error case?
>
> > Can it be merged? It applies cleanly on top of Russell's latest patch
> > (http://marc.info/?l=linux-arm-kernel&m=125638133624452&w=2).
Same question: can those 2 patches be merged in? Can they be acked-by?

> >
> > > Nicolas
> >
Thanks,
Jean
> >

---
>From 28336b68b2e2507ba0922c55147e5e72ec1a88dc Mon Sep 17 00:00:00 2001
From: Jean Pihet <jpihet@mvista.com>
Date: Tue, 27 Oct 2009 10:09:22 +0100
Subject: ARM: Check put_user fail in do_signal when enable OABI_COMPAT

Using OABI, the call to put_user in do_signal can fail. In that case
flush_icache page faults and the calling app goes in an infinite loop.

The solution is to check if put_user fails and force the app to
seg fault in that case.

Signed-off-by: janboe <janboe.ye@gmail.com>

Merged from
http://lists.infradead.org/pipermail/linux-arm-kernel/2009-October/002621.html
on top of
http://marc.info/?l=linux-arm-kernel&m=125638133624452&w=2

Tested with multiple sleeping apps/threads (using the nanosleep syscall) and
suspend/resume.

Signed-off-by: Jean Pihet <jpihet@mvista.com>
---
 arch/arm/kernel/signal.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index f330974..ea9722a 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -676,8 +676,12 @@ static int do_signal(sigset_t *oldset, struct pt_regs 
*regs, int syscall)
 				regs->ARM_sp -= 4;
 				usp = (u32 __user *)regs->ARM_sp;
 
-				put_user(regs->ARM_pc, usp);
-				regs->ARM_pc = KERN_RESTART_CODE;
+				if (put_user(regs->ARM_pc, usp) == 0) {
+					regs->ARM_pc = KERN_RESTART_CODE;
+				} else {
+					regs->ARM_sp += 4;
+					force_sigsegv(0, current);
+				}
 #endif
 			}
 		}
-- 
1.6.2.5.168.g3823