ACK: [PATCH] lib: fwts_klog: handle the case where klog_old is empty list

[ivanhu]

On 2016年02月17日 08:01, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> scan-build detected that an empty klog_old list would lead to l_old_last
> being null and hence we get a null pointer dereference when assigning
> old to the data in the null list. Check for a empty list and ensure
> l_new is initialized to NULL for this corner case.
>
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>   src/lib/src/fwts_klog.c | 21 ++++++++++++---------
>   1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/src/lib/src/fwts_klog.c b/src/lib/src/fwts_klog.c
> index 48a0e45..b5f0965 100644
> --- a/src/lib/src/fwts_klog.c
> +++ b/src/lib/src/fwts_klog.c
> @@ -51,7 +51,7 @@ void fwts_klog_free(fwts_list *klog)
>    */
>   fwts_list *fwts_klog_find_changes(fwts_list *klog_old, fwts_list *klog_new)
>   {
> -	fwts_list_link *l_old, *l_new;
> +	fwts_list_link *l_old, *l_new = NULL;
>   	fwts_list *klog_diff;
>
>   	if (klog_new == NULL) {
> @@ -74,14 +74,17 @@ fwts_list *fwts_klog_find_changes(fwts_list *klog_old, fwts_list *klog_new)
>   		fwts_list_foreach(l_old, klog_old)
>   			l_old_last = l_old;
>
> -		/* And now look for that last line in the new log */
> -		old = fwts_list_data(char *, l_old_last);
> -		fwts_list_foreach(l_new, klog_new) {
> -			char *new = fwts_list_data(char *, l_new);
> -			if (!strcmp(new, old)) {
> -				/* Found last line that matches, bump to next */
> -				l_new = l_new->next;
> -				break;
> +		if (l_old_last) {
> +			/* And now look for that last line in the new log */
> +			old = fwts_list_data(char *, l_old_last);
> +			fwts_list_foreach(l_new, klog_new) {
> +				const char *new = fwts_list_data(char *, l_new);
> +
> +				if (!strcmp(new, old)) {
> +					/* Found last line that matches, bump to next */
> +					l_new = l_new->next;
> +					break;
> +				}
>   			}
>   		}
>   	}
>

Acked-by: Ivan Hu <ivan.hu at canonical.com>