kern/39110: Suspect typecast in src/sys/dev/ld.c

[paul%whooppee.com@localhost]

>Number:         39110
>Category:       kern
>Synopsis:       Suspect typecast in src/sys/dev/ld.c
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jul 06 13:45:00 +0000 2008
>Originator:     Paul Goyette
>Release:        4.99.67
>Organization:
>Environment:
quicky:dev {285} uname -a
NetBSD quicky.whooppee.com 4.99.66 NetBSD 4.99.66 (QUICKY (ASUS M2N32 WS) 
2008-06-20 03:02:36) #1: Fri Jun 20 04:58:08 PDT 2008  
paul%speedy.whooppee.com@localhost:/build/obj/amd64/sys/arch/amd64/compile/QUICKY
 amd64
quicky:dev {286} 

>Description:
In src/sys/dev/ld.c there is a typecast of a "struct device *" to a "struct 
ld_softc *".  While this may work today due to fortuitous alignment of the 
structures, it is likely to cause problems in the future, especially if the 
"separate softc from device_t" project reaches this driver.
>How-To-Repeat:
Inspect the code
>Fix:
The following patch replaces the typecast with use of device_private().  
Although it adds a couple of instructions, it's not on a commonly-used code 
path so will have negligible performance or memory-footprint impact.

Index: ld.c
===================================================================
RCS file: /build/cvsroot/src/sys/dev/ld.c,v
retrieving revision 1.59
diff -u -p -r1.59 ld.c
--- ld.c        11 Jun 2008 12:41:22 -0000      1.59
+++ ld.c        5 Jul 2008 15:28:47 -0000
@@ -915,6 +915,6 @@ ld_set_properties(struct ld_softc *ld)
 static void
 ld_config_interrupts (struct device *d)
 {
-       struct ld_softc *sc = (struct ld_softc *)d;
+       struct ld_softc *sc = (struct ld_softc *)device_private(d);
        dkwedge_discover(&sc->sc_dk);
 }