From: Prasad J Pandit <pjp@fedoraproject.org>

Date: Thu, 22 Sep 2016 16:02:37 +0530

Subject: [PATCH] net: mcf: limit buffer descriptor count

ColdFire Fast Ethernet Controller uses buffer descriptors to manage

data flow to/fro receive & transmit queues. While transmitting

packets, it could continue to read buffer descriptors if a buffer

descriptor has length of zero and has crafted values in bd.flags.

Set upper limit to number of buffer descriptors.

Reported-by: Li Qiang <liqiang6-s@360.cn>

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Jason Wang <jasowang@redhat.com>

(cherry picked from commit 070c4b92b8cd5390889716677a0b92444d6e087a)

---

 hw/net/mcf_fec.c | 5 +++--

 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/net/mcf_fec.c b/hw/net/mcf_fec.c

index 0ee8ad9..d31fea1 100644

--- a/hw/net/mcf_fec.c

+++ b/hw/net/mcf_fec.c

@@ -23,6 +23,7 @@ do { printf("mcf_fec: " fmt , ## __VA_ARGS__); } while (0)

 #define DPRINTF(fmt, ...) do {} while(0)

 #endif

+#define FEC_MAX_DESC 1024

 #define FEC_MAX_FRAME_SIZE 2032

 typedef struct {

@@ -149,7 +150,7 @@ static void mcf_fec_do_tx(mcf_fec_state *s)

     uint32_t addr;

     mcf_fec_bd bd;

     int frame_size;

-    int len;

+    int len, descnt = 0;

     uint8_t frame[FEC_MAX_FRAME_SIZE];

     uint8_t *ptr;

@@ -157,7 +158,7 @@ static void mcf_fec_do_tx(mcf_fec_state *s)

     ptr = frame;

     frame_size = 0;

     addr = s->tx_descriptor;

-    while (1) {

+    while (descnt++ < FEC_MAX_DESC) {

         mcf_fec_read_bd(&bd, addr);

         DPRINTF("tx_bd %x flags %04x len %d data %08x\n",

                 addr, bd.flags, bd.length, bd.data);