linux-kernel - Re: [2.6 patch] kprobe_exceptions

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Message-ID: <20071029052635.GA8063@in.ibm.com>
Date:	Mon, 29 Oct 2007 10:56:35 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	Adrian Bunk <bunk@...nel.org>
Cc:	prasanna@...ibm.com, anil.s.keshavamurthy@...el.com,
	davem@...emloft.net, linux-kernel@...r.kernel.org
Subject: Re: [2.6 patch] kprobe_exceptions_notify(): fix NULL dereference

On Sat, Oct 27, 2007 at 04:19:14PM +0200, Adrian Bunk wrote:
> This patch fixes later NULL dereferences spotted by the Coverity 
> checker.
> 
> Signed-off-by: Adrian Bunk <bunk@...nel.org>

NACK... see below

> ---
> 
> BTW: The avr32 and s390 versions of kprobe_exceptions_notify() are
>      not touched since they don't contain this check.
> 
>  arch/ia64/kernel/kprobes.c    |    2 +-
>  arch/powerpc/kernel/kprobes.c |    2 +-
>  arch/sparc64/kernel/kprobes.c |    2 +-
>  arch/x86/kernel/kprobes_32.c  |    2 +-
>  arch/x86/kernel/kprobes_64.c  |    2 +-
>  5 files changed, 5 insertions(+), 5 deletions(-)
> 
> b6f1241ee20dd22210f48b4100bc5055315f3808 
> diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
> index 5fd65d8..3663dfb 100644
> --- a/arch/ia64/kernel/kprobes.c
> +++ b/arch/ia64/kernel/kprobes.c
> @@ -886,11 +886,11 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
>  				       unsigned long val, void *data)
>  {
>  	struct die_args *args = (struct die_args *)data;
>  	int ret = NOTIFY_DONE;
> 
> -	if (args->regs && user_mode(args->regs))
> +	if (args->regs || user_mode(args->regs))

This change is incorrect as you return if args->regs != NULL leading to
a sure system crash.

Ananth
-
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