From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60138) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a29Sd-0003to-EW for qemu-devel@nongnu.org; Thu, 26 Nov 2015 22:12:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a29Sc-0002tu-GI for qemu-devel@nongnu.org; Thu, 26 Nov 2015 22:12:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39903) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a29Sc-0002to-Bq for qemu-devel@nongnu.org; Thu, 26 Nov 2015 22:12:34 -0500 From: Jason Wang Date: Fri, 27 Nov 2015 11:12:21 +0800 Message-Id: <1448593943-6415-2-git-send-email-jasowang@redhat.com> In-Reply-To: <1448593943-6415-1-git-send-email-jasowang@redhat.com> References: <1448593943-6415-1-git-send-email-jasowang@redhat.com> Subject: [Qemu-devel] [PULL for-2.5 1/3] eepro100: Prevent two endless loops List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, peter.maydell@linaro.org Cc: Stefan Weil , Jason Wang From: Stefan Weil 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 Signed-off-by: Jason Wang --- 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", -- 2.5.0