Commit 00837731 authored by Stefan Weil's avatar Stefan Weil Committed by Jason Wang
Browse files

eepro100: Prevent two endless loops 

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: default avatarQinghao Tang <luodalongde@gmail.com>
Signed-off-by: default avatarStefan Weil <sw@weilnetz.de>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
parent b04fc428

hw/net/eepro100.c

+16 −0
Original line number Diff line number Diff line
@@ -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",