[v2] net: Check the argument for listen(2)

As we use u16 to save the value of the argument for listen(2),
we'd better check if the value is larger than SINT_MAX other
than cut it down silently on error.
---
 net/ipv4/af_inet.c |    3 +++
 1 file changed, 3 insertions(+)

On Sat, 2013-06-29 at 00:22 +0800, Changli Gao wrote:
> As we use u16 to save the value of the argument for listen(2),
> we'd better check if the value is larger than SINT_MAX other
> than cut it down silently on error.
> ---
>  net/ipv4/af_inet.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index b4d0be2..35aaf00 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -198,6 +198,9 @@ int inet_listen(struct socket *sock, int backlog)
>  	unsigned char old_state;
>  	int err;
>  
> +	if (backlog >= (1 << 16))
> +		return -EINVAL;
> +
>  	lock_sock(sk);
>  
>  	err = -EINVAL;


Well, there is still this possible regression for old applications.

Just use u32 fields instead of u16 ?




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On Sat, Jun 29, 2013 at 12:33 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> Well, there is still this possible regression for old applications.
>
> Just use u32 fields instead of u16 ?
>

I'll look at this. Thanks.

--
Regards,
Changli Gao(xiaosuo@gmail.com)
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On 06/28/2013 09:33 AM, Eric Dumazet wrote:

>
> Well, there is still this possible regression for old applications.
>
> Just use u32 fields instead of u16 ?

FWIW, the manpage for listen() gives the backlog parameter as an "int"

SYNOPSIS
        #include <sys/types.h>          /* See NOTES */
        #include <sys/socket.h>

        int listen(int sockfd, int backlog);

and mentions no explicit limit beyond 2.4.35, only interaction with the 
likes of /proc/sys/net/core/somaxconn.

And sys/socket.h has:

/* Prepare to accept connections on socket FD.
    N connection requests will be queued before further requests are 
refused.
    Returns 0 on success, -1 for errors.  */
extern int listen (int __fd, int __n) __THROW;

Not sure if it is considered "sane" to try to set the backlog to a 
negative value of course...

rick jones
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