Re: [rfc] netfilter: copy less data to the user

[Patrick McHardy <kaber@trash.net>]

Am 14.07.2010 23:04, schrieb Dan Carpenter:
> Smatch complains that we copy too much data to the user in ebtables.
> We copied EBT_FUNCTION_MAXNAMELEN (32) characters to the user here, but 
> "m->u.match->name" has XT_EXTENSION_MAXNAMELEN (29) characters.
> 
> I'm not sure if this is a bug where someone got confused with m->u.name
> which has 32 characters or if this is done for backwards compatability.

Looking at ebtables.h, ebt_entry_match->name uses
EBT_FUNCTION_MAXNAMELEN, which is 32 bytes. Where did you get
XT_EXTENSION_MAXNAMELEN from?

> 
> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> index 59ca00e..6bcb31d 100644
> --- a/net/bridge/netfilter/ebtables.c
> +++ b/net/bridge/netfilter/ebtables.c
> @@ -1323,7 +1323,7 @@ static inline int ebt_make_matchname(const struct ebt_entry_match *m,
>      const char *base, char __user *ubase)
>  {
>  	char __user *hlp = ubase + ((char *)m - base);
> -	if (copy_to_user(hlp, m->u.match->name, EBT_FUNCTION_MAXNAMELEN))
> +	if (copy_to_user(hlp, m->u.match->name, XT_EXTENSION_MAXNAMELEN))
>  		return -EFAULT;
>  	return 0;
>  }
> @@ -1332,7 +1332,7 @@ static inline int ebt_make_watchername(const struct ebt_entry_watcher *w,
>      const char *base, char __user *ubase)
>  {
>  	char __user *hlp = ubase + ((char *)w - base);
> -	if (copy_to_user(hlp , w->u.watcher->name, EBT_FUNCTION_MAXNAMELEN))
> +	if (copy_to_user(hlp , w->u.watcher->name, XT_EXTENSION_MAXNAMELEN))
>  		return -EFAULT;
>  	return 0;
>  }
> @@ -1356,7 +1356,7 @@ ebt_make_names(struct ebt_entry *e, const char *base, char __user *ubase)
>  	ret = EBT_WATCHER_ITERATE(e, ebt_make_watchername, base, ubase);
>  	if (ret != 0)
>  		return ret;
> -	if (copy_to_user(hlp, t->u.target->name, EBT_FUNCTION_MAXNAMELEN))
> +	if (copy_to_user(hlp, t->u.target->name, XT_EXTENSION_MAXNAMELEN))
>  		return -EFAULT;
>  	return 0;
>  }
> --
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