Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
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.
A defect in the library made it possible for a corrupt NIS request to cause the library to allocate unbounded amounts of memory and eventually crash. The library has been fixed to limit the size of NIS records to at most 16MB and no longer crashes when processing corrupt NIS requests. It is possible that some configurations with very large NIS maps may no longer work if those maps exceed the new NIS record maximum of 16MB.
Description of problem:
This issue has been found during analysing of bug #845283.
Let's have NIS client and server configured. glibc's functions like yp_match then send UDP packets to NIS server to ask for network information like login names, passwords etc. Requests are byte strings containing e.g. "...<domainname length><domainname string>...".
When we change length field of the xdr request, while the rest of the string is unchanged and pass such malformed request to the ypserv daemon for example, glibc routine allocates huge memory and then tries to read huge amount of such unallocated memory.
ypserv has a bug #845283, that causes not freeing memory when request is not parsed properly, which results in huge memory leaks and daemon failure. While freeing memory after failed parsing has to be fixed in ypserv, glibc should prevent such behaviour and not allocate more memory than necessary to avoid reading unallocated memory.
There are already limits for NIS fields like domainname, mapname, etc., but they're not used in the parsing functions. Valgrind prints then the following error:
==16566== Conditional jump or move depends on uninitialised value(s)
==16566== at 0x4A077F9: __GI_strlen (mc_replace_strmem.c:284)
==16566== by 0x51587F6: xdr_string (xdr.c:680)
==16566== by 0x4E2D5AD: xdr_ypreq_key (yp_xdr.c:50)
==16566== by 0x10B092: ypprog_2 (ypserv.c:222)
==16566== by 0x5156398: svc_getreq_common (svc.c:485)
==16566== by 0x5155ED0: svc_getreq_poll (svc.c:415)
==16566== by 0x5156A02: svc_run (svc_run.c:94)
==16566== by 0x10B84C: main (ypserv.c:726)
Using the following sane limits to NIS fields should prevent such behaviour:
#define YPMAXRECORD 1024
#define YPMAXDOMAIN 64
#define YPMAXMAP 64
#define YPMAXPEER 64
Version-Release number of selected component (if applicable):
glibc-2.12-1.80.el6.x86_64
How reproducible:
every-time
Steps to Reproduce:
1. start ypserv daemon
2. configure ypbind to use that ypserv daemon
3. create a malformed request string (example of such request will be attached as ypserv-packet-bin)
4. cat ypserv-packet-bin |nc -u 192.168.122.70 811 (192.168.122.70:811 is where ypserv listens for UDP requests)
Actual results:
huge amount of memory is allocated and then uninitialized memory is read during parsing request
Expected results:
amount of memory allocated during request parsing is limited to a sane amount
Created attachment 604885[details]
malformed request that can cause huge memory allocations
Use this like this (having ypserv listening for UDP on 192.168.122.70:788:
cat ypserv-packet-bin |nc -u 192.168.122.70 788
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-2013-1605.html