PERFORCE change 35088 for review

[Robert Watson]

http://perforce.freebsd.org/chv.cgi?CH=35088

Change 35088 by rwatson at rwatson_tislabs on 2003/07/27 07:31:34

	For the kern.file sysctl, don't reveal file descriptor
	information for processes the requesting thread isn't
	permitted to see.  This relates to PR 54211 submitted by
	Pawel Jakub Dawidek, but is a subset solution in a slightly
	different form.  Per the comment, some information about
	the total number of file descriptors is revealed, but this
	is a product of the way in which the size is calculated.
	Once we merge struct file label/access control support,
	there will also need to be a canseefile() check here.

Affected files ...

.. //depot/projects/trustedbsd/mac/sys/kern/kern_descrip.c#45 edit

Differences ...

==== //depot/projects/trustedbsd/mac/sys/kern/kern_descrip.c#45 (text+ko) ====

@@ -2305,6 +2305,14 @@
 	struct proc *p;
 	int error, n;
 
+	/*
+	 * XXXMAC
+	 * Note: because the number of file descriptors is calculated
+	 * in different ways for sizing vs returning the data,
+	 * there is information leakage from the first loop.  However,
+	 * it is of a similar order of magnitude to the leakage from
+	 * global system statistics such as kern.openfiles.
+	 */
 	sysctl_wire_old_buffer(req, 0);
 	if (req->oldptr == NULL) {
 		n = 16;		/* A slight overestimate. */
@@ -2327,6 +2335,10 @@
 	sx_slock(&allproc_lock);
 	LIST_FOREACH(p, &allproc, p_list) {
 		PROC_LOCK(p);
+		if (p_cansee(req->td, p) != 0) {
+			PROC_UNLOCK(p);
+			continue;
+		}
 		xf.xf_pid = p->p_pid;
 		xf.xf_uid = p->p_ucred->cr_uid;
 		PROC_UNLOCK(p);
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