[PATCH] packet_sendmsg_spkt incorrectly truncates an interface name

[PATCH] packet_sendmsg_spkt incorrectly truncates an interface name

[MAEDA Naoaki]

Hi,

When I renamed a network interface name with long name such as heartbeat.eth1,
DHCP client failed to assign an IP address to the interface. 

Problem is that packet_sendmsg_spkt() truncates an interface name 
by 12 characters. That is why the following dev_get_by_name() fails to find
the corresponding net_device structure.

Obviously, max name length of a network interface name is IFNAMESIZ-1, 
which is 15. I can not come up with any reasonable reason that
packet_sendmsg_spkt() should truncate the interface name by 12.
I guess it is just a trivial bug.

The following patch fix the problem.

Thanks,
Naoaki

diff -Naur linux-2.6.2.org/net/packet/af_packet.c linux-2.6.2/net/packet/af_packet.c
--- linux-2.6.2.org/net/packet/af_packet.c	2004-02-10 15:29:14.160320269 +0900
+++ linux-2.6.2/net/packet/af_packet.c	2004-02-10 15:29:52.656413548 +0900
@@ -311,7 +311,7 @@
 	 *	Find the device first to size check it 
 	 */
 
-	saddr->spkt_device[13] = 0;
+	saddr->spkt_device[IFNAMSIZ-1] = 0;
 	dev = dev_get_by_name(saddr->spkt_device);
 	err = -ENODEV;
 	if (dev == NULL)

Re: [PATCH] packet_sendmsg_spkt incorrectly truncates an interface name

[Andrew Morton]

MAEDA Naoaki <maeda.naoaki@jp.fujitsu.com> wrote:
>
> Hi,
> 
> When I renamed a network interface name with long name such as heartbeat.eth1,
> DHCP client failed to assign an IP address to the interface. 
> 
> Problem is that packet_sendmsg_spkt() truncates an interface name 
> by 12 characters. That is why the following dev_get_by_name() fails to find
> the corresponding net_device structure.

You need to use a shorter name, I think.

> Obviously, max name length of a network interface name is IFNAMESIZ-1, 
> which is 15.

Yes, but sockaddr_pkt.spkt_device[] is only 14 bytes for some reason.

> I can not come up with any reasonable reason that
> packet_sendmsg_spkt() should truncate the interface name by 12.
> I guess it is just a trivial bug.

These objects are shared with userspace applications, I believe.  We're
stuck with it.


> diff -Naur linux-2.6.2.org/net/packet/af_packet.c linux-2.6.2/net/packet/af_packet.c
> --- linux-2.6.2.org/net/packet/af_packet.c	2004-02-10 15:29:14.160320269 +0900
> +++ linux-2.6.2/net/packet/af_packet.c	2004-02-10 15:29:52.656413548 +0900
> @@ -311,7 +311,7 @@
>  	 *	Find the device first to size check it 
>  	 */
>  
> -	saddr->spkt_device[13] = 0;
> +	saddr->spkt_device[IFNAMSIZ-1] = 0;
>  	dev = dev_get_by_name(saddr->spkt_device);
>  	err = -ENODEV;
>  	if (dev == NULL)

This scribbles on sockaddr_pkt.spkt_protocol.

Probably what we need to do here is to put a bit of range-checking into the
userspace tool.  Is it nameif?

Re: [PATCH] packet_sendmsg_spkt incorrectly truncates an interface name

[MAEDA Naoaki]

Hi,

> > Obviously, max name length of a network interface name is IFNAMESIZ-1, 
> > which is 15.
> 
> Yes, but sockaddr_pkt.spkt_device[] is only 14 bytes for some reason.

Oops! I have not checked it.
Does anybody know the reason why it is only 14 bytes?

Thanks,
Naoaki

Re: [PATCH] packet_sendmsg_spkt incorrectly truncates an interface name

[Raj]

On Tue, 10 Feb 2004, MAEDA Naoaki wrote:

> Hi,
> 
> > > Obviously, max name length of a network interface name is IFNAMESIZ-1, 
> > > which is 15.
> > 
> > Yes, but sockaddr_pkt.spkt_device[] is only 14 bytes for some reason.
> 
> Oops! I have not checked it.
> Does anybody know the reason why it is only 14 bytes?
>
include/linux/socket.h
struct sockaddr {
...
char sa_data[14]; /* 14 bytes of protocol address */
};

A 14 byte field here too !. Maybe there is an explanation. 

/Raj
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