Subject: Re: [PATCH 1/3] [PKT_SCHED]: Fix illegal memory dereferences when dumping actions

From: Patrick McHardy <[email-masked]>
Date: Wed, 05 Jul 2006 01:42:46 +0200

Thomas Graf wrote:
> The TCA_ACT_KIND attribute is used without checking its
> availability when dumping actions therefore leading to a
> value of 0x4 being dereferenced.
> 
> The use of strcmp() in tc_lookup_action_n() isn't safe
> when fed with string from an attribute without enforcing
> proper NUL termination.
> 
> Both bugs can be triggered with malformed netlink message
> and don't require any privileges.
> 
> Signed-off-by: Thomas Graf <[email-masked]>
> 
> Index: net-2.6.git/net/sched/act_api.c
> ===================================================================
> --- net-2.6.git.orig/net/sched/act_api.c
> +++ net-2.6.git/net/sched/act_api.c
> @@ -776,7 +776,7 @@ replay:
>  	return ret;
>  }
>  
> -static char *
> +static struct rtattr *
>  find_dump_kind(struct nlmsghdr *n)
>  {
>  	struct rtattr *tb1, *tb2[TCA_ACT_MAX+1];
> @@ -804,7 +804,7 @@ find_dump_kind(struct nlmsghdr *n)
>  		return NULL;
>  	kind = tb2[TCA_ACT_KIND-1];
>  
> -	return (char *) RTA_DATA(kind);
> +	return kind;
>  }
>  
>  static int
> @@ -817,16 +817,15 @@ tc_dump_action(struct sk_buff *skb, stru
>  	struct tc_action a;
>  	int ret = 0;
>  	struct tcamsg *t = (struct tcamsg *) NLMSG_DATA(cb->nlh);
> -	char *kind = find_dump_kind(cb->nlh);
> +	struct rtattr *kind = find_dump_kind(cb->nlh);
>  
>  	if (kind == NULL) {
>  		printk("tc_dump_action: action bad kind\n");
>  		return 0;
>  	}
>  
> -	a_o = tc_lookup_action_n(kind);
> +	a_o = tc_lookup_action(kind);
>  	if (a_o == NULL) {
> -		printk("failed to find %s\n", kind);
>  		return 0;
>  	}
>  
> @@ -834,7 +833,7 @@ tc_dump_action(struct sk_buff *skb, stru
>  	a.ops = a_o;
>  
>  	if (a_o->walk == NULL) {
> -		printk("tc_dump_action: %s !capable of dumping table\n", kind);
> +		printk("tc_dump_action: %s !capable of dumping table\n", a_o->kind);
>  		goto rtattr_failure;
>  	}

Can't we just get rid of these printks? This seems like a good
opportunity.