Re: [PATCH 1/3] netfilter: Fix copy_to_user too small size parametre.
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: 2012-03-01 10:18:17
Also in:
bridge, kernel-janitors, lkml, netfilter-devel
On Thu, Mar 01, 2012 at 02:46:30PM +0530, santosh nayak wrote:
From: Santosh Nayak <redacted> 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.
quoted hunk ↗ jump to hunk
Signed-off-by: Santosh Nayak <redacted> --- 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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html