From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Subject: [patch] fix stack overflow in pktgen_if_write() Date: Thu, 28 Oct 2010 00:12:35 +0200 Message-ID: <20101027221234.GN6062@bicker> References: <1288206788-21063-1-git-send-email-nelhage@ksplice.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Dumazet , "David S. Miller" , Robert Olsson , Andy Shevchenko , netdev@vger.kernel.org To: nelhage@ksplice.com Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:64210 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031Ab0J0WMs (ORCPT ); Wed, 27 Oct 2010 18:12:48 -0400 Received: by wwe15 with SMTP id 15so1330790wwe.1 for ; Wed, 27 Oct 2010 15:12:47 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1288206788-21063-1-git-send-email-nelhage@ksplice.com> Sender: netdev-owner@vger.kernel.org List-ID: Nelson Elhage says he was able to oops both amd64 and i386 test machines with 8k writes to the pktgen file. Let's just allocate the buffer on the heap instead of on the stack. This can only be triggered by root so there are no security issues here. Reported-by: Nelson Elhage Signed-off-by: Dan Carpenter --- I saw this on twitter. Hi Nelson, could you test this? diff --git a/net/core/pktgen.c b/net/core/pktgen.c index 2c0df0f..b5d3c70 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -887,12 +887,14 @@ static ssize_t pktgen_if_write(struct file *file, i += len; if (debug) { - char tb[count + 1]; - if (copy_from_user(tb, user_buffer, count)) - return -EFAULT; - tb[count] = 0; + char *tb; + + tb = strndup_user(user_buffer, count + 1); + if (IS_ERR(tb)) + return PTR_ERR(tb); printk(KERN_DEBUG "pktgen: %s,%lu buffer -:%s:-\n", name, (unsigned long)count, tb); + kfree(tb); } if (!strcmp(name, "min_pkt_size")) {