Driver crash with cardbus & auto-configuration

[M. Warner Losh]

Sorry to top post, but this is really a bug in sio, and should be
fixed there.  I've added some comments to the driver, but didn't fix
it since that's a little trickier than I'd thought when I dove in...

Warner

In message: <Pine.GSO.4.21.0810072312220.4889-100000 at nova41.dc.engr.scu.edu>
            "Dorr H. Clark" <dclark at engr.scu.edu> writes:
: 
: Driver crash with cardbus & auto-configuration:
: 
: This situation was encountered when trying to use a laptop with 
: cardbus CIS for the COEN284 "UNIX Kernel Internals" class at SCU.
: 
: The corruption was discovered after applying a patch to allow 
: the cardbus CIS to be parsed (see BUG #115623 ).  After a reboot of 
: the laptop (DELL latitude CPx), the auto-configuration process of 
: the cardbus XIRCOM RBEM56G provoked a crash.
: 
: The root cause of the crash is the corruption of the malloc storage
: itself.  The corruption happened in the auto-configuration process.   
: As the kernel is probing various possible devices, one call 
: corrupts memory, & it was found that bce_probe() is the culprit.
: The code causing the crash in the 'bce' driver is only to allow
: a debug printf, and therefore can be safely removed.
:  
: The explanation of the corruption is as follows:  while 
: probing for child, we normally allocate and deallocate the 
: softc structure of the corresponding driver.  In this 
: auto-configuration case, the 'sio' driver was probed prior 
: to the 'bce' driver and the sio driver was allocating the original 
: 'softc' memory.  The softc is set with size of 812 bytes 
: (the sio softc data struct), and the dev->flags is set with 
: DF_EXTERNALSOFTC.  This flag makes sure that the softc is not 
: deallocated, and the following probe re-uses the same softc.  
: However, when the bce_probe gets executed, it re-interprets 
: the softc data structure into a 'struct bce_softc' of size 8852 
: and then scribbles beyond the end of the original allocation
: corrupting memory.
: 
: While we encountered this issue with 7.0, it appears that this 
: is an issue in the latest version and also could be a problem in 
: the 6.3 release.
: 
: A recommended patch for this problem is offered below.
: 
: Charles Bransi
: Engineer
: 
: Dorr H. Clark
: Advisor
: 
: Graduate School of Engineering
: Santa Clara University
: Santa Clara, CA
: 
: http://www.cse.scu.edu/~dclark/coen_284_FreeBSD/driver_crash.txt
: 
:     The change is the following:
:  
: --- if_bce_orig.c 2008-07-30 21:47:15.000000000 -0700
: +++ if_bce.c 2008-08-01 21:02:52.000000000 -0700
: @@ -394,27 +394,17 @@
:  bce_probe(device_t dev)
:  {
:  	struct bce_type *t;
: -	struct bce_softc *sc;
:  	char *descbuf;
:  	u16 vid = 0, did = 0, svid = 0, sdid = 0;
:  
:  	t = bce_devs;
:  
: -	sc = device_get_softc(dev);
: -	bzero(sc, sizeof(struct bce_softc));
: -	sc->bce_unit = device_get_unit(dev);
: -	sc->bce_dev = dev;
: -
:  	/* Get the data for the device to be probed. */
:  	vid  = pci_get_vendor(dev);
:  	did  = pci_get_device(dev);
:  	svid = pci_get_subvendor(dev);
:  	sdid = pci_get_subdevice(dev);
:  
: -	DBPRINT(sc, BCE_VERBOSE_LOAD, 
: -		"%s(); VID = 0x%04X, DID = 0x%04X, SVID = 0x%04X, "
: -		"SDID = 0x%04X\n", __FUNCTION__, vid, did, svid, sdid);
: -
:  	/* Look through the list of known devices for a match. */
:  	while(t->bce_name != NULL) {
:  
: 
: 
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