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Date: Tue, 12 May 2009 21:26:38 +0530
From: Subrata Modak <subrata@...ux.vnet.ibm.com>
To: <x86@...nel.org>
Cc: Sachin P Sant <sachinp@...ux.vnet.ibm.com>,
Andi Kleen <andi@...stfloor.org>,
Andi Kleen <ak@...ux.intel.com>,
Linux Kernel <linux-kernel@...r.kernel.org>,
Subrata Modak <subrata@...ux.vnet.ibm.com>,
Balbir Singh <balbir@...ux.vnet.ibm.com>
Subject: [PATCH] Fix Warnining in arch/x86/kernel/signal.c
Hi,
>On Tue, 2009-05-12 at 17:16 +0200, Andi Kleen wrote:
>On Tue, May 12, 2009 at 05:16:14PM +0530, Subrata Modak wrote:
>
> Hi Subrata,
>
> >
> > With gcc (GCC) 4.4.1 20090429 (prerelease), i get the following build warning:
>
> Patch looks good (you can add a
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>)
> But I don't maintain this code anymore. Please resend to x86@...nel.org
> cc linux-kernel@...r.kernel.org for merge.
>
> Thanks,
>
> -Andi
With gcc (GCC) 4.4.1 20090429 (prerelease), i get the following build warning:
CC arch/x86/kernel/signal.o
arch/x86/kernel/signal.c: In function ‘sys_sigreturn’:
arch/x86/kernel/signal.c:573: warning: ‘set.sig[1]’ may be used uninitialized in this function
On investigation i found that this is because of the evaluation
precedence of the expression below:
569 unsigned long sys_sigreturn(struct pt_regs *regs)
570 {
571 struct sigframe __user *frame;
572 unsigned long ax;
573 sigset_t set;
574
575 frame = (struct sigframe __user *)(regs->sp - 8);
576
577 if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
578 goto badframe;
579 if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
580 && __copy_from_user(&set.sig[1], &frame->extramask,
581 sizeof(frame->extramask))))
The initialization for set.sig[1] may not occur if
__get_user(set.sig[0], &frame->sc.oldmask)
evalutes to true. So, the compiler is complaining.
I have devised a small patch for this which wanes away this warning
without changing the conditional evaluation criteria. Let me know if
you like this patch.
582 goto badframe;
583
584 sigdelsetmask(&set, ~_BLOCKABLE);
585 spin_lock_irq(¤t->sighand->siglock);
586 current->blocked = set;
587 recalc_sigpending();
588 spin_unlock_irq(¤t->sighand->siglock);
589
590 if (restore_sigcontext(regs, &frame->sc, &ax))
591 goto badframe;
592 return ax;
593
594 badframe:
595 signal_fault(regs, frame, "sigreturn");
596
597 return 0;
598 }
Signed-Off-By: Subrata Modak <subrata@...ux.vnet.ibm.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
To: <x86@...nel.org>
Cc: Linux Kernel <linux-kernel@...r.kernel.org>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc: Sachin P Sant <sachinp@...ux.vnet.ibm.com>
Subject: [PATCH] Fix Warnining in arch/x86/kernel/signal.c
---
--- a/arch/x86/kernel/signal.c 2009-05-12 10:59:24.000000000 +0530
+++ b/arch/x86/kernel/signal.c 2009-05-12 16:57:32.000000000 +0530
@@ -576,9 +576,10 @@ unsigned long sys_sigreturn(struct pt_re
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
- if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
- && __copy_from_user(&set.sig[1], &frame->extramask,
- sizeof(frame->extramask))))
+
+ if ( (__copy_from_user(&set.sig[1], &frame->extramask,
+ sizeof(frame->extramask)) && _NSIG_WORDS > 1) ||
+ __get_user(set.sig[0], &frame->sc.oldmask))
goto badframe;
sigdelsetmask(&set, ~_BLOCKABLE);
---
Regards--
Subrata
--
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