kern/83999: [patch] panic in fw_bus_explore due to NULL reference

[Markus Wild]

>Number:         83999
>Category:       kern
>Synopsis:       [patch] panic in fw_bus_explore due to NULL reference
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Jul 24 13:40:23 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Markus Wild
>Release:        current amd64
>Organization:
>Environment:
FreeBSD amd64.dudes.ch 7.0-CURRENT FreeBSD 7.0-CURRENT #29: Sat Jul 16 18:30:24 CEST 2005     mw at amd64.dudes.ch:/usr/obj/usr/src/sys/AMD64  amd64

>Description:
Machine panics at

fw_bus_explore+0x3f: testb $0x40,0x(%rax)

with %rax being NULL. 

The problem is the line (1339):
       if (!fw_find_self_id(fc, fc->ongonode)->p0.link_active) {

fw_find_self_id() can return 0 if it doesn't find the node. This  is
not taken into account with the above test.

>How-To-Repeat:
On this machine it was sufficient to load the firewire module to
trigger the panic. A canopus ADV module was plugged into the 
firewire port. 

>Fix:
diff -u -r1.80 firewire.c
--- firewire.c  6 Jan 2005 01:42:41 -0000       1.80
+++ firewire.c  24 Jul 2005 13:37:09 -0000
@@ -1324,6 +1324,7 @@
        uint32_t addr;
        struct fw_xfer *xfer;
        struct fw_pkt *fp;
+       union fw_self_id *fwsid;
 
        if(fc->status != FWBUSEXPLORE)
                return;
@@ -1336,7 +1337,8 @@
 
        /* check link */
        /* XXX we need to check phy_id first */
-       if (!fw_find_self_id(fc, fc->ongonode)->p0.link_active) {
+       fwsid = fw_find_self_id(fc, fc->ongonode);
+       if (!fwsid || !fwsid->p0.link_active) {
                if (firewire_debug)
                        printf("node%d: link down\n", fc->ongonode);
                fc->ongonode++;

>Release-Note:
>Audit-Trail:
>Unformatted: