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When exporting file descriptor data for threads invoking the

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kern.file sysctl, don't return information about processes that
fail p_cansee(td, p).  This prevents sockstat and related
programs from seeing file descriptors owned by processes not
in the same jail as the thread, as well as having implications
for MAC, etc.

This is a partial solution: it permits an information leak about
the number of descriptors in the sizing calculation (but this is
not new information, you can also get it from kern.openfiles),
and doesn't attempt to mask file descriptors based on the
properties of the descriptor, only the process referencing it.
However, it provides most of what you want under most
circumstances, without complicating the locking.

PR:	54211
Based on a patch submitted by:	Pawel Jakub Dawidek <nick@garage.freebsd.pl>
This commit is contained in:
Robert Watson 2003-07-28 16:03:53 +00:00
parent 239a15f305
commit 2e4a71cdb1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=118126
1 changed files with 11 additions and 0 deletions
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11
sys/kern/kern_descrip.c
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@ -2273,6 +2273,13 @@ sysctl_kern_file(SYSCTL_HANDLER_ARGS)
struct proc *p;
int error, n;
/*
* 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. */
@ -2295,6 +2302,10 @@ sysctl_kern_file(SYSCTL_HANDLER_ARGS)
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);