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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: Qinghao Tang <luodalongde@gmail.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Stefan Weil 2015-11-20 08:42:33 +01:00 committed by Jason Wang
parent b04fc42835
commit 00837731d2
1 changed files with 16 additions and 0 deletions
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16
hw/net/eepro100.c
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@ -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",