Subject: Re: Resend [PATCH] netfilter: Fix copy_to_user too small size parametre.

From: Pablo Neira Ayuso <[email-masked]>
Date: Sun, 4 Mar 2012 13:18:41 +0100

On Thu, Mar 01, 2012 at 10:39:03PM +0530, santosh nayak wrote:
> From: Santosh Nayak <[email-masked]>
> 
> user-space ebtables expects 32 bytes-long names, but xt_match uses
> 29 bytes. Fill the remaining bytes with zeroes.
> 
> Signed-off-by: Santosh Nayak <[email-masked]>
> ---
>  net/bridge/netfilter/ebtables.c |   14 +++++++++++---
>  1 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> index 5864cc4..21f337a 100644
> --- a/net/bridge/netfilter/ebtables.c
> +++ b/net/bridge/netfilter/ebtables.c
> @@ -1335,7 +1335,10 @@ 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))
> +	char name[EBT_FUNCTION_MAXNAMELEN] = {};
> +
> +	strncpy(name, m->u.match->name, sizeof(name));
> +	if (copy_to_user(hlp, name, EBT_FUNCTION_MAXNAMELEN))
>  		return -EFAULT;
>  	return 0;
>  }
> @@ -1344,7 +1347,10 @@ 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))
> +	char name[EBT_FUNCTION_MAXNAMELEN] = {};
> +
> +	strncpy(name, w->u.watcher->name, sizeof(name));
> +	if (copy_to_user(hlp , name, EBT_FUNCTION_MAXNAMELEN))
>  		return -EFAULT;
>  	return 0;
>  }
> @@ -1355,10 +1361,12 @@ ebt_make_names(struct ebt_entry *e, const char *base, char __user *ubase)
>  	int ret;
>  	char __user *hlp;
>  	const struct ebt_entry_target *t;
> +	char name[EBT_FUNCTION_MAXNAMELEN] = {};
>  
>  	if (e->bitmask == 0)
>  		return 0;
>  
> +	strncpy(name, t->u.target->name, sizeof(name));
>  	hlp = ubase + (((char *)e + e->target_offset) - base);
>  	t = (struct ebt_entry_target *)(((char *)e) + e->target_offset);

This is broken, t dereference is incorrect. Unfortunately I've applied
your patch. I'll apply a patch to fix this upon it.