From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Thu, 02 Apr 2026 09:21:57 +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 1w8CNJ-007lhw-1f for lore@lore.pengutronix.de; Thu, 02 Apr 2026 09:21:57 +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 1w8CNI-0008T1-UF for lore@pengutronix.de; Thu, 02 Apr 2026 09:21:57 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:To:In-Reply-To: References:Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version: Subject:Date:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=EjBtrjcwDjPbmC8X7EBCgdm/91y/glJXqo0YoUwf+v8=; b=toiREDoOZTj393sqUAJrS2bw19 +M3MOGAu9OIIbTVIRtpKINxXErt4eeUFSjMvojGDvAF/lcHrs+jZZgzXK+h/2eammtNkNQonyZTzp 59R37sfe9kz+j2MPsQuwHC188FGGGUbZ3yiIioN9fi1Ptw6P4CY7hgUJs3wuhfxn8DZoDTMx11zX6 0vKh5SqhqJ68VQ2Gv+UKvqrzDCG2GFZ5nLTa+1yUcANk0aEg3LLBlFIaWpqeBUCLaQ/Yg5WbNiEuf AyxDy9SjMmlSISit8brUCeIu14RkEHV4LfEH3183CaR2LflQoyK/BHNdVRUh9a79ogIhH4W9hmPNK +x9AF2tw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w8CMv-0000000H2L3-0kKw; Thu, 02 Apr 2026 07:21:33 +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 1w8CMt-0000000H2IS-0nQJ for barebox@lists.infradead.org; Thu, 02 Apr 2026 07:21:32 +0000 Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1w8CMj-0008Dd-PA; Thu, 02 Apr 2026 09:21:21 +0200 Received: from dude02.red.stw.pengutronix.de ([2a0a:edc0:0:1101:1d::28]) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1w8CMj-003Kwg-1k; Thu, 02 Apr 2026 09:21:21 +0200 Received: from [::1] (helo=dude02.red.stw.pengutronix.de) by dude02.red.stw.pengutronix.de with esmtp (Exim 4.98.2) (envelope-from ) id 1w8CMj-00000003PEH-1q6A; Thu, 02 Apr 2026 09:21:21 +0200 From: Sascha Hauer Date: Thu, 02 Apr 2026 09:21:21 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260402-net-tftp-buffer-overflows-v1-3-0a18aa8ea19e@pengutronix.de> References: <20260402-net-tftp-buffer-overflows-v1-0-0a18aa8ea19e@pengutronix.de> In-Reply-To: <20260402-net-tftp-buffer-overflows-v1-0-0a18aa8ea19e@pengutronix.de> To: BAREBOX X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1775114481; l=1195; i=s.hauer@pengutronix.de; s=20230412; h=from:subject:message-id; bh=IL92QsX57h9sKvcWSRGxpZdRQKVUtXfam+3h6VvIcwc=; b=sh85Jyc3qZyp/KHdwLVwcd2lU1jq/BrrR/b8+N06VHTv6yThjspVEXKNNdIBcXFmBv5ePwB4g UiW3DEBvX2PAxzYxrNasxD7pg7t/nx3gDKy0aJPT1Kvj82k66o4K26B X-Developer-Key: i=s.hauer@pengutronix.de; a=ed25519; pk=4kuc9ocmECiBJKWxYgqyhtZOHj5AWi7+d0n/UjhkwTg= X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260402_002131_242388_C9195E99 X-CRM114-Status: GOOD ( 11.08 ) 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: , Cc: "Claude Opus 4.6 \(1M context\)" 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: [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) 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) --- 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"); -- 2.47.3