information about kernel locking issue - An important detail

information about kernel locking issue - An important detail

[Giacomo S.]

Sorry, i did not specify an important detail:

this function is invoked by a series of other functions, the first of those is 
hooked
tol the netfilter hooks.

So, depending on the 'direction' of the flow (input, output, fwd), we are
in user context (for output) or soft interrupt (in, fwd).

----------  Messaggio inoltrato  ----------

Subject: information about kernel locking issue
Date: 13:55, sabato 1 luglio 2006
From: "Giacomo S." <delleceste@gmail.com>
To: netfilter-devel@lists.netfilter.org

Good morning.

Some time ago i wrote a module in kernel space which does some filtering.

While running `dhclient eth0'  and plugging/unplugging the ethernet cable
from the network card, kernel freezed saying the culprit was the following
function (EIP is at get_ifaddr_by_name() ) :

/* returns in *addr the internet address having the name ifname */
int get_ifaddr_by_name(const char *ifname, __u32 * addr)
{
       struct net_device *pnet_device;
       struct in_device *pin_device;

       read_lock_bh(&dev_base_lock);
       pnet_device = dev_base;
       while (pnet_device != NULL)
         {
                 if ((netif_running(pnet_device))
                     && (pnet_device->ip_ptr != NULL)
                     && (strcmp(pnet_device->name, ifname) == 0))
                   {
                           pin_device =
                               (struct in_device *) pnet_device->ip_ptr;
                           /* ifa_local: ifa_address is the remote point in
ppp */
                           *addr = (pin_device->ifa_list->ifa_local);
                           read_unlock_bh(&dev_base_lock);
                           return 1;
                   }
                pnet_device = pnet_device->next;
         }
         read_unlock_bh(&dev_base_lock);
       return -1;              /* address not found! */
}

What could be wrong?
I think the problem is that read_lock_bh is not correct, perhaps
i would need read_lock_irq instead??

Can anyone suggest if i am right.

Thanks a lot

Giacomo.
--
Giacomo S.

www.giacomos.it

em@il:
delleceste@gmail.com
jacum@libero.it
giacomo.strangolino@elettra.trieste.it


Running IPFIRE-wall on debian GNU/Linux:
www.giacomos.it/ipfire

www.debian.org

-------------------------------------------------------

-- 
Giacomo S.

www.giacomos.it

em@il:
delleceste@gmail.com
jacum@libero.it
giacomo.strangolino@elettra.trieste.it
 	

Running IPFIRE-wall on debian GNU/Linux:
www.giacomos.it/ipfire

www.debian.org