bridge: netfilter: fix information leak

commit d846f71195d57b0bbb143382647c2c6638b04c5a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 0b7f262cd14861aaf21849ee522b3d110c3370d3..d73d47f2a4add9512f48a7bf32ee30b0eb410888 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -979,6 +979,8 @@ static int do_replace(struct net *net, void __user *user, unsigned int len)
        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)