Re: [PATCH] avoid out of bounds array reference in save_trace()

[Peter Zijlstra <peterz@infradead.org>]

On Wed, 2009-12-09 at 14:29 -0800, Luck, Tony wrote:
> ia64 found this the hard way (because we currently have a stub for
> save_stack_trace() that does nothing). But it would be a good idea to 
> be cautious in case a real save_stack_trace() bailed out with an
> error before it set trace->nr_entries.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>

Thanks Tony,

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

> ---
> 
> diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> index 03c06af..429540c 100644
> --- a/kernel/lockdep.c
> +++ b/kernel/lockdep.c
> @@ -387,7 +387,8 @@ static int save_trace(struct stack_trace *trace)
>  	 * complete trace that maxes out the entries provided will be reported
>  	 * as incomplete, friggin useless </rant>
>  	 */
> -	if (trace->entries[trace->nr_entries-1] == ULONG_MAX)
> +	if (trace->nr_entries != 0 &&
> +	    trace->entries[trace->nr_entries-1] == ULONG_MAX)
>  		trace->nr_entries--;
>  
>  	trace->max_entries = trace->nr_entries;