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>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 59ca00e40dec2401b483bad4a7799775766e9f0d..62675dc51179b14d04b0e27daf39730f75ed2d19 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1098,6 +1098,8 @@ 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)