netdev - Re: [PATCH] ipv4: kernel panic when only one unsecured port available

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Date:	Wed, 10 Oct 2007 10:54:52 +0400
From:	"Denis V. Lunev" <den@...ru>
To:	Anton Arapov <aarapov@...hat.com>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4: kernel panic when only one unsecured port available

This code is broken from the very beginning.

iris den # cat /proc/sys/net/ipv4/ip_local_port_range
32768   61000
iris den # echo 32768 32 >/proc/sys/net/ipv4/ip_local_port_range
iris den # cat /proc/sys/net/ipv4/ip_local_port_range
32768   32
iris den # echo 32768 61000 >/proc/sys/net/ipv4/ip_local_port_range

Regards,
	Den

Anton Arapov wrote:
> Steps to reproduce:
> Server:
>   [root@...ver ~]# cat /etc/exports
>   /export *(ro,insecure)
> // there is insecure ... I am using ports like "1024 to 61000"
>   [root@...ver ~] service nfs restart 
> 
> Client:
>   1.[root@...ent ~]# echo 32768 32768 > /proc/sys/net/ipv4/ip_local_port_range
>   32768   32768
> // two same numbers, for ex "32769 32769" etc.
>   2.[root@...ent ~]# cat /proc/sys/net/ipv4/ip_local_port_range
>   32768   32768
>   3.[root@...ent ~]# mount server:/export /import
>   
> Actual results:
>   Kernel always panics 
> 
> --------------------------------------------------------------------
> [PATCH] ipv4: kernel panic when only one unsecured port available
> 
>   Patch prevents division by zero. Kernel panics if only one 
> unsecured port available.
> 
> Signed-off-by: Anton Arapov <aarapov@...hat.com>
> ---
> 
>  net/ipv4/inet_connection_sock.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index fbe7714..00ad079 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -80,7 +80,7 @@ int inet_csk_get_port(struct inet_hashinfo *hashinfo,
>  		int low = sysctl_local_port_range[0];
>  		int high = sysctl_local_port_range[1];
>  		int remaining = (high - low) + 1;
> -		int rover = net_random() % (high - low) + low;
> +		int rover = net_random() % remaining + low;
>  
>  		do {
>  			head = &hashinfo->bhash[inet_bhashfn(rover, hashinfo->bhash_size)];
> 

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