bridge: netfilter: fix information leak

Struct tmp is copied from userspace.  It is not checked whether the "name"
field is NULL terminated.  This may lead to buffer overflow and passing
contents of kernel stack as a module name to try_then_request_module() and,
consequently, to modprobe commandline.  It would be seen by all userspace
processes.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 5f1825df9dcad7cb546ae7b4b8182210cd60d7a5..893669caa8de6c56960f804da8d2125f07823fb3 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1107,6 +1107,8 @@ static int do_replace(struct net *net, const void __user *user,
        if (tmp.num_counters >= INT_MAX / sizeof(struct ebt_counter))
                return -ENOMEM;
 
+       tmp.name[sizeof(tmp.name) - 1] = 0;
+
        countersize = COUNTER_OFFSET(tmp.nentries) * nr_cpu_ids;
        newinfo = vmalloc(sizeof(*newinfo) + countersize);
        if (!newinfo)