Re: No hrSWRunPath in HOST-RESOURCES-MIB

On 31/03/09 0:20 , "Dave Shield" <[email protected]> wrote:
> 2009/3/30 Kamil Kisiel <[email protected]>:
>> Right, so now that we know the symptoms, I guess the question is why does
>> this only happen on the version of Net-SNMP that openSUSE ships? Despite
>> using the same version number on my Gentoo machines, the hrSWRunPath works
>> fine there for all processes. For the kernel level processes it just returns
>> the process name.
> 
> Try comparing the output of    "cat /proc/2'/status"   on the two systems.
> Do you see similar output in both cases?
> Or is the openSuSE version empty?
> 
> Thomas' output has confirmed that it's the handling of the /proc/{pid}/status
> file which is triggering this problem.    Now we just need to come up with a
> better long-term fix.

I decided to dive in to the source code of hr_swrun.c and found the
following:

 728 #elif defined(linux)
 729         sprintf(string, "/proc/%d/cmdline", pid);
 730         if ((fp = fopen(string, "r")) == NULL) {
 731             strcpy(string, "<exited>");
 732             *var_len = strlen(string);
 733             return (u_char *) string;
 734         }
 735         if (fgets(buf, sizeof(buf) - 1, fp))    /* argv[0] '\0' argv[1]
'\0' .... */
 736             strcpy(string, buf);
 737         else {
 738             /*
 739              * swapped out - no cmdline
 740              */
 741             fclose(fp);
 742             sprintf(string, "/proc/%d/status", pid);
 743             if ((fp = fopen(string, "r")) == NULL)
 744                 return NULL;
 745             fgets(buf, sizeof(buf), fp);        /* Name: process name
*/
 746             if ( cp == NULL ) {
 747                 fclose(fp);
 748                 return NULL;    /* the process probably died */
 749             }
 750             cp = strchr(buf, ':');
 751             if ( cp == NULL ) {
 752                 fclose(fp);
 753                 return NULL;    /* the process file is malformed */
 754             }
 755             ++cp;
 756             while (isspace(*cp))
 757                 ++cp;
 758             strcpy(string, cp);
 759             cp = strchr(string, '\n');
 760             if (cp)
 761                 *cp = 0;

It seems to me there's an error at line 746. Why is it checking to see if
"cp" (presumably "char pointer") is NULL after reading a line in to "buf"?
Should it not be checking if "buf" is NULL instead at this point?

I'm thinking that perhaps on the systems where this works properly "cp" may
have been initialized by chance. It's used extensively in the preceding code
for a whole bunch of string manipulations.



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