RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Bug 1028643 - Connection remains when fork() fails.
Summary: Connection remains when fork() fails.
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: openssh
Version: 6.4
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: ---
Assignee: Petr Lautrbach
QA Contact: Patrik Kis
URL:
Whiteboard:
Depends On:
Blocks: 1070830
TreeView+ depends on / blocked
 
Reported: 2013-11-09 00:50 UTC by Tetsuo Handa
Modified: 2018-12-09 17:16 UTC (History)
4 users (show)

Fixed In Version: openssh-5.3p1-97.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
: 1029074 (view as bug list)
Environment:
Last Closed: 2014-10-14 07:39:41 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
fix cleanup in openssh-5.3p1-audit.patch (641 bytes, patch)
2013-11-11 15:33 UTC, Petr Lautrbach 		no flags Details | Diff
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2014:1552 0 normal SHIPPED_LIVE Moderate: openssh security, bug fix, and enhancement update 2014-10-14 01:21:23 UTC

Description Tetsuo Handa 2013-11-09 00:50:00 UTC 
Description of problem:

Please see upstream bug report at https://bugzilla.mindrot.org/show_bug.cgi?id=2167 .
I attached a fix in that report. Please backport to RHEL/Fedora's openssh
package when the fix is committed, for this bug actually blocked an unattended
ssh session (execution of batched job) of an enterprise server.

Version-Release number of selected component (if applicable):

Any.

How reproducible:

100% reproducible when fork() in privsep_postauth() fails.

Steps to Reproduce:

1. Build as usual like "rpmbuild -bb openssh.spec".
2. Go to the build directory and replace fork() in privsep_postauth() in sshd.c
   with -1 and rebuild using "make".
3. Run ./sshd and try to connect as an unprivileged user.

Actual results:

Connection cannot be closed when fork() fails.

Expected results:

Connection should be closed immediately when fork() fails.
Comment 2 Petr Lautrbach 2013-11-11 15:33:52 UTC 
Created attachment 822474 [details]
fix cleanup in openssh-5.3p1-audit.patch

Please apply this patch on your openssh-5.3p1-audit.patch from src.rpm and check if it help you.
Comment 3 Tetsuo Handa 2013-11-12 05:47:15 UTC 
Hello. Thank you for the patch.

The patch fixes fork() failure case in privsep_postauth() but does not fix
fork() failure case in privsep_preauth(), for pmonitor->m_pid == 0 in the
latter function.

I don't know whether it is safe to change privsep_preauth() from

  pid = fork();
  if (pid == -1) {
    fatal("fork of unprivileged child failed");
  } else if (pid != 0) {

to

  pmonitor->m_pid = fork();
  if (pmonitor->m_pid == -1) {
    fatal("fork of unprivileged child failed");
  } else if (pmonitor->m_pid != 0) {

like privsep_postauth() does. But at least changing privsep_preauth() like

   pid = fork();
   if (pid == -1) {
+    pmonitor->m_pid = -1
     fatal("fork of unprivileged child failed");
   } else if (pid != 0) {

can fix fork() failure case in privsep_preauth().

Regards.
Comment 4 Petr Lautrbach 2013-11-12 15:38:16 UTC 
Thanks for testing. You are right about privsep_preauth(). I personally would use:

@@ -633,7 +683,7 @@ privsep_preauth(Authctxt *authctxt)
 	/* Store a pointer to the kex for later rekeying */
 	pmonitor->m_pkex = &xxx_kex;
 
-	pid = fork();
+	pmonitor->m_pid = pid = fork();
 	if (pid == -1) {
 		fatal("fork of unprivileged child failed");
 	} else if (pid != 0) {


but it's only a cosmetic change. The fix will be included in the update.
Comment 10 errata-xmlrpc 2014-10-14 07:39:41 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2014-1552.html
Note You need to log in before you can comment on or make changes to this bug.