[PATCH] crash in pcmcia_access_configuration_register

[PATCH] crash in pcmcia_access_configuration_register

[Pavel Roskin]

Hello!

As promised, here's the patch to fix an oops in the kernel PCMCIA driver.
The patch should be applied both to 2.4 and 2.5 series.

How to reproduce the bug:

1) Compile and install HostAP (http://hostap.epitest.fi/) - any recent
version (CVS version is OK).

2) Insert a card supported by HostAP.

3) Remove (physically) the card.  The kernel oopses.

Explanation:

While doing a reset, HostAP used AccessConfigurationRegister request to
preserve the value of the configuration register.  The reset is triggered
by the removal of the card.

I do believe that HostAP can be improved to avoid reset if the socket
configuration has been released.  Nevertheless, oops is not a reputable
behavior when the driver merely requests a configuration register.

The pcmcia-cs driver already has a slightly different protection, but the
following patch is simpler and addresses the problem right before it
happens.

====================================
--- drivers/pcmcia/cs.c
+++ drivers/pcmcia/cs.c
@@ -882,6 +882,10 @@ int pcmcia_access_configuration_register
 	c = &s->config[reg->Function];
     } else
 	c = CONFIG(handle);
+
+    if (c == NULL)
+	return CS_NO_CARD;
+
     if (!(c->state & CONFIG_LOCKED))
 	return CS_CONFIGURATION_LOCKED;

====================================

-- 
Regards,
Pavel Roskin