From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail-pl1-f182.google.com (mail-pl1-f182.google.com [209.85.214.182]) by mx.groups.io with SMTP id smtpd.web08.8688.1663654966783915502 for ; Mon, 19 Sep 2022 23:22:46 -0700 Authentication-Results: mx.groups.io; dkim=pass header.i=@gmail.com header.s=20210112 header.b=IzCyRSBW; spf=pass (domain: gmail.com, ip: 209.85.214.182, mailfrom: imv4bel@gmail.com) Received: by mail-pl1-f182.google.com with SMTP id jm5so412330plb.13 for ; Mon, 19 Sep 2022 23:22:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=NTji0+RBPiysZFHQBiYPWwLSVVlat0nxjjCKSq+cwbM=; b=IzCyRSBWX8YWf5Br/YwXc5rqkhD02O/1wdyWt2QvjSirUIgE9OL8KOrS571pwXVyWI jryYjbm3SHhgDmi96Z7u9TBpMpyViys5rBypNa7FnpwIjTwJ6NMz6AsmvXAteCuODwC0 jmghsGOaczTH6ERjZF7nlv9M1M3bsiZxm6oUbAgyvxrk3LbpSs34kR+489mYsnmTAHg/ ghGsg23SrecnoxEngcUGr4BnqFPkj6voCNKyN6uwWsw4gpnllWPGs0oZ7pTuuUlhFyuy ybowHEUmQKI8Yj04J/V/VDyUTTyJebuy/wL3fXhTgxxgYIOJ39BzbcgPTa/kIxru0gs7 qOVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=NTji0+RBPiysZFHQBiYPWwLSVVlat0nxjjCKSq+cwbM=; b=XCdthjCxnDhz90AyLG+2b92kqswrT+o0gNNI1IHGm5bNOv7N5DVsAC4VcdRFvDc+lO SIRAsYsg7ondLLUKR2FNcQ3waOgMbENvXxJRkdfXZ9juuDtjkwwtgzPAja0ertInt2eA YP1n4CxhshINn1+T/V/LfKX8Unxg5tRteOP3hub7Eka8NQGkAamBzMRR/zp52tMdoU8j pjJqakMbjMSSRzR8bT8S6oZjC27/e/t8gyN+mmgygdA9QPM9uS99MMPWrJiOY2+dXa5b MMODz7bofFKiF2DUOuVGF5azONkouI/q+NesMnMqHRxUwDHU0TgoGx99/iMh5Oe8UJrl PFHQ== X-Gm-Message-State: ACrzQf2lxqmtq8vrA4yEDkYsoICA2bsmQQnYuG5A06+klech+2H97xXF eWyznYaLTWfDTptlKfaaxp4= X-Google-Smtp-Source: AMsMyM6pAFi14MIftTxpTT6kP/Mg8xeHEGdJ9k4i6zFuXXjUv/mmIhMQK/yQevcbjMJ2qjiEo6vt7w== X-Received: by 2002:a17:902:c40e:b0:178:4931:cc4d with SMTP id k14-20020a170902c40e00b001784931cc4dmr3326380plk.97.1663654965979; Mon, 19 Sep 2022 23:22:45 -0700 (PDT) Return-Path: Received: from ubuntu ([175.124.254.119]) by smtp.gmail.com with ESMTPSA id w16-20020a170902e89000b001725d542190sm509896plg.181.2022.09.19.23.22.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Sep 2022 23:22:45 -0700 (PDT) Date: Mon, 19 Sep 2022 23:22:41 -0700 From: Hyunwoo Kim To: Dan Carpenter Cc: deller@gmx.de, linux-fbdev@vger.kernel.org, Masami Ichikawa , cip-dev , Harshit Mogalapalli Subject: Re: [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write Message-ID: <20220920062241.GA321122@ubuntu> References: MIME-Version: 1.0 In-Reply-To: Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: On Tue, Sep 20, 2022 at 09:13:31AM +0300, Dan Carpenter wrote: > On Tue, Sep 20, 2022 at 09:02:34AM +0300, Dan Carpenter wrote: > > On Mon, Jun 20, 2022 at 07:00:10AM -0700, Hyunwoo Kim wrote: > > > In pxa3xx_gcu_write, a count parameter of > > > type size_t is passed to words of type int. > > > Then, copy_from_user may cause a heap overflow because > > > it is used as the third argument of copy_from_user. > > > > > > Signed-off-by: Hyunwoo Kim > > > --- > > > drivers/video/fbdev/pxa3xx-gcu.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/video/fbdev/pxa3xx-gcu.c b/drivers/video/fbdev/pxa3xx-gcu.c > > > index 043cc8f9ef1c..c3cd1e1cc01b 100644 > > > --- a/drivers/video/fbdev/pxa3xx-gcu.c > > > +++ b/drivers/video/fbdev/pxa3xx-gcu.c > > > @@ -381,7 +381,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff, > > > struct pxa3xx_gcu_batch *buffer; > > > struct pxa3xx_gcu_priv *priv = to_pxa3xx_gcu_priv(file); > > > > > > - int words = count / 4; > > > + size_t words = count / 4; > > > > The count variable is actually capped at MAX_RW_COUNT in vfs_write() > > so "words" cannot be negative. This patch helps clean up the code but > > it does not affect run time. > > Btw, the other thing which prevents this from being expliotable is that > if you pass a negative value to copy_from_user() it will not copy > anything because of the check in check_copy_size(). See commit > 6d13de1489b6 ("uaccess: disallow > INT_MAX copy sizes"). > > Linus has sort of gotten annoyed with me before for pointing this stuff > out because it seemed like maybe I wasn't properly grateful to people > auditing the code and fixing bugs. I am grateful. This patch is > totally the correct thing to do. It's just that it's not really > exploitable as described in the commit message. I found the code that might have the vulnerability, and submitted a patch without actually debugging it. This is entirely my fault. sorry. Should I submit a fix patch that fixes the commit message? Sorry again. Regards, Hyunwoo Kim.