dhcpcd-discuss

On 10/09/2018 18:54, Stuart Henderson wrote:
> On 2018/09/10 13:45, Shahid Mahmood wrote:
> > Hi Roy,
> > Our coverity analysis reported the following defect. Just so you know:
> >
> >   63static size_t
> >   64duid_machineuuid(char *uuid, size_t uuid_len)
> >   65{
> >   66        int r;
> >   67        size_t len = uuid_len;
> > ....
>
> It makes more sense if you fill in the "..." :

Yes, the context here is very important.

>   68
>   69 #if defined(HW_UUID) /* OpenBSD */
>   70         int mib[] = { CTL_HW, HW_UUID };
>   71
>   72         r = sysctl(mib, sizeof(mib)/sizeof(mib[0]), uuid, &len, NULL, 0);
>   73 #elif defined(KERN_HOSTUUID) /* FreeBSD */
>   74         int mib[] = { CTL_KERN, KERN_HOSTUUID };
>   75
>   76         r = sysctl(mib, sizeof(mib)/sizeof(mib[0]), uuid, &len, NULL, 0);
>   77 #elif defined(__NetBSD__)
>   78         r = sysctlbyname("machdep.dmi.system-uuid", uuid, &len, NULL, 0);
>   79 #elif defined(__linux__)
>   80         FILE *fp;
>   81
>   82         fp = fopen("/sys/class/dmi/id/product_uuid", "r");
>   83         if (fp == NULL)
>   84                 return 0;
> > 85        if (fgets(uuid, (int)uuid_len, fp) == NULL) {
> >   86                fclose(fp);
> >   87                return 0;
> >   88        }
> >   89        len = strlen(uuid) + 1;
> >   90        fclose(fp);
> >     
> > [Coverity]assignment: Assigning: r = 0.
> >   91        r = 0;
> >   92#else
> >   93        r = -1;
> >   94        errno = ENOSYS;
> >   95#endif
> >   96
> >     
> > [Coverity] const: At condition r == -1, the value of r must be equal to 0.
> >     
> > [Coverity] dead_error_condition: The condition r == -1 cannot be true.
>
> there are other OS than Linux ..

Indeed there are.
No matter how impossible it is to silence warnings compiling dhcpcd on 
Linux (and there are a LOT which pains me), we should still silence 
where we can. It's not the first time coverity has detected false 
positives before either.

The attached patch should solve it - I can't test it as coverity does 
not work on my one Linux VM.
Let me know if it works for you!

> >   97        if (r == -1)
> >     
> > [Coverity]  Logically dead code (DEADCODE)dead_error_line: Execution cannot reach this
> > statement: return 0U;.
> >   98                return 0;
> >   99        return len;
> > 100}
> >
> > Regards,
> > -shahid

Roy

diff --git a/src/duid.c b/src/duid.c
index cc53f9bd..45223435 100644
--- a/src/duid.c
+++ b/src/duid.c
@@ -94,6 +94,7 @@ duid_machineuuid(char *uuid, size_t uuid_len)
 	errno = ENOSYS;
 #endif
 
+	/* coverity[dead_error_condition] False positive on Linux */
 	if (r == -1)
 		return 0;
 	return len;