Re: [Qemu-devel] [PATCH v2] net: mcf: limit buffer descriptor count

[Paolo Bonzini <pbonzini@redhat.com>]

On 22/09/2016 12:32, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> 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>
> ---
>  hw/net/mcf_fec.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> Update per
>   -> https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg05284.html
> 
> diff --git a/hw/net/mcf_fec.c b/hw/net/mcf_fec.c
> index 7c0398e..6d3418e 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);
> 

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