Note: This is a public test instance of Red Hat Bugzilla. The data contained within is a snapshot of the live data so any changes you make will not be reflected in the production Bugzilla. Email is disabled so feel free to test any aspect of the site that you want. File any problems you find or give feedback at bugzilla.redhat.com.
Bug 1213603 - glibc: nss_db: get*ent crashes without preceding set*ent
Summary: glibc: nss_db: get*ent crashes without preceding set*ent
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: glibc
Version: 7.2
Hardware: All
OS: Linux
urgent
medium
Target Milestone: rc
: ---
Assignee: Florian Weimer
QA Contact: Sergey Kolosov
URL:
Whiteboard:
Depends On: 1344480
Blocks: 1388635
TreeView+ depends on / blocked
 
Reported: 2015-04-20 21:39 UTC by Frank Hirtz
Modified: 2020-02-14 17:29 UTC (History)
11 users (show)

Fixed In Version: glibc-2.17-158.el7
Doc Type: Bug Fix
Doc Text:
Cause: The nss_db Name Service Switch module incorrectly initializes itself. Consequence: If nss_db is enabled and any of the get*ent functions (such as getservent) are called before a corresponding set*ent call, the application crashes. Fix: The nss_db initialization sequence was updated to support this call sequence. Result: It is possible to call get*ent functions without calling set*ent first.
Clone Of:
: 1344480 1388635 (view as bug list)
Environment:
Last Closed: 2017-08-01 18:06:55 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Bugzilla 1318890 0 urgent CLOSED glibc: nss_db: long group entries are skipped 2022-05-16 11:32:56 UTC
Red Hat Bugzilla 1370630 0 high CLOSED glibc: nss_db: Endless loop in services database processing 2022-05-16 11:32:56 UTC
Red Hat Bugzilla 1698015 0 medium CLOSED glibc: Calling getpwent after endpwent should not crash? 2022-05-16 11:32:56 UTC
Red Hat Product Errata RHSA-2017:1916 0 normal SHIPPED_LIVE Moderate: glibc security, bug fix, and enhancement update 2017-08-01 18:05:43 UTC
Sourceware 20237 0 None None None 2019-06-13 20:41:09 UTC

Internal Links: 1318890 1370630 1698015

Description Frank Hirtz 2015-04-20 21:39:15 UTC 
Description of problem:
Baseline, with nsswitch set to use db, but no .db files. This works:

<snip>
root@garabaldi ~]# grep services /etc/nsswitch.conf | grep -v '^#'
services:   db files sss
[root@garabaldi ~]# rm -f /var/db/*
rm: cannot remove ‘/var/db/sudo’: Is a directory
[root@garabaldi ~]# perl -e getservent
[root@garabaldi ~]# 
<snip>

Now let;s build a default db file set (this is a clean install):

<snip>
[root@garabaldi ~]# perl -e getservent
[root@garabaldi ~]# cd /var/db/; make; cd -
passwd... done.
group... done.
protocols... done.
rpc... done.
services... done.
shadow... done.

Warning: The shadow password database /var/db/shadow.db
has been set to be readable only by root.  You may want
to make it readable by the `shadow' group depending
on your configuration.

gshadow... done.

Warning: The shadow group database /var/db/gshadow.db
has been set to be readable only by root.  You may want
to make it readable by the `shadow' group depending
on your configuration.

/root
[root@garabaldi ~]# perl -e getservent
Segmentation fault
<snip>
Core was generated by `perl -e getservent'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007f90955685bf in __rawmemchr_sse2 () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install perl-5.16.3-285.el7.x86_64
(gdb) bt
#0  0x00007f90955685bf in __rawmemchr_sse2 () from /lib64/libc.so.6
#1  0x00007f908eba81c1 in _nss_db_getservent_r () from /lib64/libnss_db.so.2
#2  0x00007f90955e0c11 in __nss_getent_r () from /lib64/libc.so.6
#3  0x00007f90955e983a in getservent_r@@GLIBC_2.2.5 () from /lib64/libc.so.6
#4  0x00007f9096931a96 in Perl_pp_gservent () from /usr/lib64/perl5/CORE/libperl.so
#5  0x00007f90968dca46 in Perl_runops_standard ()
   from /usr/lib64/perl5/CORE/libperl.so
#6  0x00007f9096879855 in perl_run () from /usr/lib64/perl5/CORE/libperl.so
#7  0x0000000000400d99 in main ()
<snip>

Version-Release number of selected component (if applicable):
glibc-2.17-78.el7.x86_64

How reproducible:


Steps to Reproduce:
1. Set nsswitch to use 'db' for services
    > grep services /etc/nsswitch.conf | grep -v '^#'
    > services:   db files sss
2. cd /var/db/; make; cd -
3. perl -e getservent

Actual results:
Segfault

Expected results:
No Segfault

Additional info:
Comment 3 Florian Weimer 2015-12-15 18:14:49 UTC 
It appears the cause is that that implicit initialization of the service by get*ent (without a preceding set*ent) does not cause initialization of the entidex variable.  _nss_db_get*_r does this:

   247	  if (state.header == NULL)
   248	    {
   249	      status = internal_setent (DBFILE, &state);
   250	      if (status != NSS_STATUS_SUCCESS)
   251		{
   252		  *errnop = errno;
   253		  H_ERRNO_SET (NETDB_INTERNAL);
   254		  goto out;
   255		}
   256	    }

While _nss_db_set* has:

    72	  status = internal_setent (DBFILE, &state);
    73	
    74	  if (status == NSS_STATUS_SUCCESS)
    75	    {
    76	      /* Remember STAYOPEN flag.  */
    77	      keep_db |= stayopen;
    78	
    79	      /* Reset the sequential index.  */
    80	      entidx  = (const char *) state.header + state.header->valstroffset;
    81	    }

As far as I can see, the bug is present upstream as well.
Comment 5 Florian Weimer 2016-06-10 08:56:08 UTC 
Patch posted upstream:

  https://sourceware.org/ml/libc-alpha/2016-06/msg00346.html
Comment 8 Florian Weimer 2016-06-13 05:11:33 UTC 
Upstream fix:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=31d0a4fa646db8b8c97ce24e0ec0a7b73de4fca1
Comment 25 errata-xmlrpc 2017-08-01 18:06:55 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.

https://access.redhat.com/errata/RHSA-2017:1916
Note You need to log in before you can comment on or make changes to this bug.