From patchwork Fri Nov 20 07:42:33 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Weil X-Patchwork-Id: 546827 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 56C6D140D7F for ; Fri, 20 Nov 2015 18:42:55 +1100 (AEDT) Received: from localhost ([::1]:45764 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzgLN-0001pK-8l for incoming@patchwork.ozlabs.org; Fri, 20 Nov 2015 02:42:53 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34741) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzgL8-0001V4-UH for qemu-devel@nongnu.org; Fri, 20 Nov 2015 02:42:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZzgL7-0005mf-UU for qemu-devel@nongnu.org; Fri, 20 Nov 2015 02:42:38 -0500 Received: from qemu.weilnetz.de ([2a03:4000:2:362::1]:43036) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzgL7-0005mM-OC for qemu-devel@nongnu.org; Fri, 20 Nov 2015 02:42:37 -0500 Received: by qemu.weilnetz.de (Postfix, from userid 1000) id 06F8D17F6EB; Fri, 20 Nov 2015 08:42:34 +0100 (CET) From: Stefan Weil To: QEMU Developer , Peter Maydell Date: Fri, 20 Nov 2015 08:42:33 +0100 Message-Id: <1448005353-16007-1-git-send-email-sw@weilnetz.de> X-Mailer: git-send-email 2.1.4 X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2a03:4000:2:362::1 Cc: Paolo Bonzini , Jason Wang , Stefan Weil , ppandit@redhat.com Subject: [Qemu-devel] [PATCH for-2.5] eepro100: Prevent two endless loops X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg04592.html shows an example how an endless loop in function action_command can be achieved. During my code review, I noticed a 2nd case which can result in an endless loop. Reported-by: Qinghao Tang Signed-off-by: Stefan Weil --- hw/net/eepro100.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c index 60333b7..685a478 100644 --- a/hw/net/eepro100.c +++ b/hw/net/eepro100.c @@ -774,6 +774,11 @@ static void tx_command(EEPRO100State *s) #if 0 uint16_t tx_buffer_el = lduw_le_pci_dma(&s->dev, tbd_address + 6); #endif + if (tx_buffer_size == 0) { + /* Prevent an endless loop. */ + logout("loop in %s:%u\n", __FILE__, __LINE__); + break; + } tbd_address += 8; TRACE(RXTX, logout ("TBD (simplified mode): buffer address 0x%08x, size 0x%04x\n", @@ -855,6 +860,10 @@ static void set_multicast_list(EEPRO100State *s) static void action_command(EEPRO100State *s) { + /* The loop below won't stop if it gets special handcrafted data. + Therefore we limit the number of iterations. */ + unsigned max_loop_count = 16; + for (;;) { bool bit_el; bool bit_s; @@ -870,6 +879,13 @@ static void action_command(EEPRO100State *s) #if 0 bool bit_sf = ((s->tx.command & COMMAND_SF) != 0); #endif + + if (max_loop_count-- == 0) { + /* Prevent an endless loop. */ + logout("loop in %s:%u\n", __FILE__, __LINE__); + break; + } + s->cu_offset = s->tx.link; TRACE(OTHER, logout("val=(cu start), status=0x%04x, command=0x%04x, link=0x%08x\n",