ACK: [Trusty SRU][CVE-2016-8633][PATCH] firewire: net: guard against rx buffer overflows

[Stefan Bader]

On 07.09.2017 15:02, Kleber Sacilotto de Souza wrote:
> From: Stefan Richter <stefanr at s5r6.in-berlin.de>
> 
> CVE-2016-8633
> 
> The IP-over-1394 driver firewire-net lacked input validation when
> handling incoming fragmented datagrams.  A maliciously formed fragment
> with a respectively large datagram_offset would cause a memcpy past the
> datagram buffer.
> 
> So, drop any packets carrying a fragment with offset + length larger
> than datagram_size.
> 
> In addition, ensure that
>   - GASP header, unfragmented encapsulation header, or fragment
>     encapsulation header actually exists before we access it,
>   - the encapsulated datagram or fragment is of nonzero size.
> 
> Reported-by: Eyal Itkin <eyal.itkin at gmail.com>
> Reviewed-by: Eyal Itkin <eyal.itkin at gmail.com>
> Fixes: CVE 2016-8633
> Cc: stable at vger.kernel.org
> Signed-off-by: Stefan Richter <stefanr at s5r6.in-berlin.de>
> (cherry picked from commit 667121ace9dbafb368618dbabcf07901c962ddac)
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---
> 
> Notes:
>     Only Trusty still needs the fix for this CVE. Cherry pick applies cleanly,
>     compile tested.
>     
>     Kleber
> 
>  drivers/firewire/net.c | 51 ++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 35 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
> index 4af0a7bad7f2..641eeab43c57 100644
> --- a/drivers/firewire/net.c
> +++ b/drivers/firewire/net.c
> @@ -591,6 +591,9 @@ static int fwnet_incoming_packet(struct fwnet_device *dev, __be32 *buf, int len,
>  	int retval;
>  	u16 ether_type;
>  
> +	if (len <= RFC2374_UNFRAG_HDR_SIZE)
> +		return 0;
> +
>  	hdr.w0 = be32_to_cpu(buf[0]);
>  	lf = fwnet_get_hdr_lf(&hdr);
>  	if (lf == RFC2374_HDR_UNFRAG) {
> @@ -615,7 +618,12 @@ static int fwnet_incoming_packet(struct fwnet_device *dev, __be32 *buf, int len,
>  		return fwnet_finish_incoming_packet(net, skb, source_node_id,
>  						    is_broadcast, ether_type);
>  	}
> +
>  	/* A datagram fragment has been received, now the fun begins. */
> +
> +	if (len <= RFC2374_FRAG_HDR_SIZE)
> +		return 0;
> +
>  	hdr.w1 = ntohl(buf[1]);
>  	buf += 2;
>  	len -= RFC2374_FRAG_HDR_SIZE;
> @@ -629,6 +637,9 @@ static int fwnet_incoming_packet(struct fwnet_device *dev, __be32 *buf, int len,
>  	datagram_label = fwnet_get_hdr_dgl(&hdr);
>  	dg_size = fwnet_get_hdr_dg_size(&hdr); /* ??? + 1 */
>  
> +	if (fg_off + len > dg_size)
> +		return 0;
> +
>  	spin_lock_irqsave(&dev->lock, flags);
>  
>  	peer = fwnet_peer_find_by_node_id(dev, source_node_id, generation);
> @@ -735,6 +746,22 @@ static void fwnet_receive_packet(struct fw_card *card, struct fw_request *r,
>  	fw_send_response(card, r, rcode);
>  }
>  
> +static int gasp_source_id(__be32 *p)
> +{
> +	return be32_to_cpu(p[0]) >> 16;
> +}
> +
> +static u32 gasp_specifier_id(__be32 *p)
> +{
> +	return (be32_to_cpu(p[0]) & 0xffff) << 8 |
> +	       (be32_to_cpu(p[1]) & 0xff000000) >> 24;
> +}
> +
> +static u32 gasp_version(__be32 *p)
> +{
> +	return be32_to_cpu(p[1]) & 0xffffff;
> +}
> +
>  static void fwnet_receive_broadcast(struct fw_iso_context *context,
>  		u32 cycle, size_t header_length, void *header, void *data)
>  {
> @@ -744,9 +771,6 @@ static void fwnet_receive_broadcast(struct fw_iso_context *context,
>  	__be32 *buf_ptr;
>  	int retval;
>  	u32 length;
> -	u16 source_node_id;
> -	u32 specifier_id;
> -	u32 ver;
>  	unsigned long offset;
>  	unsigned long flags;
>  
> @@ -763,22 +787,17 @@ static void fwnet_receive_broadcast(struct fw_iso_context *context,
>  
>  	spin_unlock_irqrestore(&dev->lock, flags);
>  
> -	specifier_id =    (be32_to_cpu(buf_ptr[0]) & 0xffff) << 8
> -			| (be32_to_cpu(buf_ptr[1]) & 0xff000000) >> 24;
> -	ver = be32_to_cpu(buf_ptr[1]) & 0xffffff;
> -	source_node_id = be32_to_cpu(buf_ptr[0]) >> 16;
> -
> -	if (specifier_id == IANA_SPECIFIER_ID &&
> -	    (ver == RFC2734_SW_VERSION
> +	if (length > IEEE1394_GASP_HDR_SIZE &&
> +	    gasp_specifier_id(buf_ptr) == IANA_SPECIFIER_ID &&
> +	    (gasp_version(buf_ptr) == RFC2734_SW_VERSION
>  #if IS_ENABLED(CONFIG_IPV6)
> -	     || ver == RFC3146_SW_VERSION
> +	     || gasp_version(buf_ptr) == RFC3146_SW_VERSION
>  #endif
> -	    )) {
> -		buf_ptr += 2;
> -		length -= IEEE1394_GASP_HDR_SIZE;
> -		fwnet_incoming_packet(dev, buf_ptr, length, source_node_id,
> +	    ))
> +		fwnet_incoming_packet(dev, buf_ptr + 2,
> +				      length - IEEE1394_GASP_HDR_SIZE,
> +				      gasp_source_id(buf_ptr),
>  				      context->card->generation, true);
> -	}
>  
>  	packet.payload_length = dev->rcv_buffer_size;
>  	packet.interrupt = 1;
> 


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