From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Fri, 17 Apr 2026 11:33:10 +0200 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1wDfZW-00D8tz-04 for lore@lore.pengutronix.de; Fri, 17 Apr 2026 11:33:10 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1wDfZV-00025M-En for lore@pengutronix.de; Fri, 17 Apr 2026 11:33:09 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=sH9IgUUmxM4GeCVpFZW3rjxIZaFqiZ/s/VTqZmoiL/g=; b=J5I1LY0dvLt2FL3G3qTponPAdB vzbYCfHLUyICpK0BGu8CzuyR2/dJ64TSEpGSsWRSDDJl8a6K2cDt6pYgroXiWpdQ3Bt0cyM/emeV3 7bxLm2IkCSqbEpzjLTrXcTBx2McxdP/O6SRPSFXUFWWFOfZOB4CQXUxsfi1+gD1OqkizayfA4nNTb 790BqAAc+61dUrz4FNIMGXAmOq7xbkjwNSC2C7LNAmX//oDchiPyaed9PxPepl6HO6jfVL/2EuAdj 4OyqleD7gjB3F2587NkvcsgABeCR/4fgq3XCXBnS6PHZaU3u045rZL3dRV8vRTkuBjIvrYifNt41z 78i8cqTw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDfZ7-00000003pwF-2YPE; Fri, 17 Apr 2026 09:32:45 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDfZ5-00000003pvt-1Rnq for barebox@lists.infradead.org; Fri, 17 Apr 2026 09:32:44 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1wDfZ3-0001ux-Q2; Fri, 17 Apr 2026 11:32:41 +0200 Message-ID: <82b0da9a-1e6c-4f55-b96c-c208115c76c7@pengutronix.de> Date: Fri, 17 Apr 2026 11:32:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer , BAREBOX Cc: "Claude Opus 4.6 (1M context)" References: <20260402-net-tftp-buffer-overflows-v1-0-0a18aa8ea19e@pengutronix.de> <20260402-net-tftp-buffer-overflows-v1-3-0a18aa8ea19e@pengutronix.de> From: Ahmad Fatoum Content-Language: en-US, de-DE, de-BE In-Reply-To: <20260402-net-tftp-buffer-overflows-v1-3-0a18aa8ea19e@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260417_023243_390685_6F8651B4 X-CRM114-Status: GOOD ( 18.33 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.2 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 3/4] fs: tftp: reject OACK with blocksize of zero X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) Hi, On 4/2/26 9:21 AM, Sascha Hauer wrote: > tftp_parse_oack() validates that windowsize is non-zero but does not > check blocksize. A malicious TFTP server sending 'blksize\0000\0' in > the OACK sets priv->blocksize to 0, which causes: > > - kfifo_alloc(0 * ...) allocating a zero-sized fifo > - tftp_write() entering an infinite loop on > 'while (kfifo_len(fifo) >= 0)', spinning on kfifo_get with size 0 > - tftp_put_data() rejecting all data packets as oversized > > Add blocksize == 0 to the existing OACK validation check. > > Signed-off-by: Sascha Hauer > Co-Authored-By: Claude Opus 4.6 (1M context) Reviewed-by: Ahmad Fatoum > --- > fs/tftp.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/tftp.c b/fs/tftp.c > index 03e9d552aa..6dd4829184 100644 > --- a/fs/tftp.c > +++ b/fs/tftp.c > @@ -382,7 +382,8 @@ static int tftp_parse_oack(struct file_priv *priv, unsigned char *pkt, int len) > s = val + strlen(val) + 1; > } > > - if (priv->blocksize > TFTP_MTU_SIZE || > + if (priv->blocksize == 0 || > + priv->blocksize > TFTP_MTU_SIZE || > priv->windowsize > TFTP_MAX_WINDOW_SIZE || > priv->windowsize == 0) { > pr_warn("tftp: invalid oack response\n"); > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |