sysctl_kern_proc doesn't handle the case when no procs match given criteria

[Dima Dorfman]

Hello -hackers

The sysctl_kern_proc routine in kern_proc.c doesn't handle the case
when no processes match the given criteria.  I.e., if no processes
match, it will return 0 even though it never called SYSCTL_OUT; thus,
the output data is junk.  This can be demonstrated by giving ps(1)
arguments such that no processes match.  In this example, the user
`nobody' isn't running anything:

        dd@ref5% ps U nobody
        ps: kinfo_proc size mismatch (expected 648, got -791621424)

Obviously, this isn't the desired mode of failure.  Attached is a
patch that will make sysctl_kern_proc return ESRCH if it didn't find
any processes.  AFAIK, without the patch, the only way to detect this
condition (no processes match search criteria) is to check that a call
into this routine via sysctl didn't modify whatever is pointed at by
the oldp pointer (see sysctl(3)).

Comments?  Suggestions?

Thanks

                                        Dima Dorfman
                                        [EMAIL PROTECTED]

P.S.  libkvm and/or ps(1) should probably be taught to check for this
condition and react more gently (on -stable, ps just prints the column
labels when this happens).  I'll probably do this later.

Index: kern_proc.c
===================================================================
RCS file: /st/src/FreeBSD/src/sys/kern/kern_proc.c,v
retrieving revision 1.89
diff -u -r1.89 kern_proc.c
--- kern_proc.c 2001/03/07 06:52:12     1.89
+++ kern_proc.c 2001/03/17 04:20:49
@@ -555,6 +555,7 @@
        struct proc *p;
        int doingzomb;
        int error = 0;
+       int match = 0;
 
        if (oidp->oid_number == KERN_PROC_PID) {
                if (namelen != 1) 
@@ -640,9 +641,12 @@
                                ALLPROC_LOCK(AP_RELEASE);
                                return (error);
                        }
+                       match = 1;
                }
        }
        ALLPROC_LOCK(AP_RELEASE);
+       if (!match)
+               return (ESRCH);
        return (0);
 }
 


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