On Thu, Mar 01, 2012 at 02:46:30PM +0530, santosh nayak wrote:
> From: Santosh Nayak <santoshprasadnayak@xxxxxxxxx>
>
> While copying to userspace, the size of source is 29byte where as
> size parametre is 32 byte. Its leaking extra-information from
> kernel space to user space.
> Replace EBT_FUNCTION_MAXNAMELEN by XT_EXTENSION_MAXNAMELEN.
There's no information leak.
Let me clarify this. Have a look at /linux/netfilter/x_tables.h, then
you find:
#define XT_FUNCTION_MAXNAMELEN 30
#define XT_EXTENSION_MAXNAMELEN 29
#define XT_TABLE_MAXNAMELEN 32
For iptables, everything has been 30 bytes, but we stole one
byte to store the revision field for matches/targets.
For ebtables, there's no revision field and the length of the
table name is different.
But linux/netfilter/in ebtables.h, you'll find:
#define EBT_TABLE_MAXNAMELEN 32
#define EBT_CHAIN_MAXNAMELEN EBT_TABLE_MAXNAMELEN
#define EBT_FUNCTION_MAXNAMELEN EBT_TABLE_MAXNAMELEN
Note that someone decided to use 32 bytes for the ebtables
tables/match/target name instead of 30 bytes in iptables.
Yes, it sucks a bit we have to live with these interfaces until
we have some netlink interface for all these things.
> Signed-off-by: Santosh Nayak <santoshprasadnayak@xxxxxxxxx>
> ---
> net/bridge/netfilter/ebtables.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> index 5864cc4..f3fcbd9 100644
> --- a/net/bridge/netfilter/ebtables.c
> +++ b/net/bridge/netfilter/ebtables.c
> @@ -1335,7 +1335,7 @@ 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;
> }
> @@ -1344,7 +1344,7 @@ 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;
> }
> @@ -1368,7 +1368,7 @@ 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;
> }
> --
> 1.7.4.4
>
> --
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