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Bug 1624542 - Fix use-after-free in rpc.statd monitor list when insertion fails for existing entry
Summary: Fix use-after-free in rpc.statd monitor list when insertion fails for existin...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: nfs-utils
Version: 7.5
Hardware: Unspecified
OS: Unspecified
medium
unspecified
Target Milestone: rc
: ---
Assignee: Steve Dickson
QA Contact: Yongcheng Yang
URL:
Whiteboard:
Depends On:
Blocks: 1577173
TreeView+ depends on / blocked
 
Reported: 2018-09-01 05:12 UTC by Frank Sorenson
Modified: 2021-12-10 17:16 UTC (History)
4 users (show)

Fixed In Version: nfs-utils-1.3.0-0.62.el7
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2019-08-06 13:11:50 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
patch to fix statd use-after-free (821 bytes, text/plain)
2018-09-01 05:12 UTC, Frank Sorenson 		no flags Details
reproducer for bz1624542 (1.22 KB, application/x-shellscript)
2018-09-03 17:32 UTC, Frank Sorenson 		no flags Details
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2019:2268 0 None None None 2019-08-06 13:11:59 UTC

Description Frank Sorenson 2018-09-01 05:12:44 UTC 
Created attachment 1480181 [details]
patch to fix statd use-after-free

Description of problem:

If nsm_insert_monitored_host() fails while saving the record to stable storage, we currently just free the entry and return with error.  This can lead to a use-after-free, causing rpc.statd to crash.

We can't just assume the entry was new. Existing records must be removed from the list before being freed.


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

all


How reproducible:

easy


Steps to Reproduce:

using the test program nsm_client:

# /tmp/nsm_client mon client1 1
# /tmp/nsm_client mon client2 1

chown -R root:root /var/lib/nfs/statd/sm{,.bak}

# /tmp/nsm_client mon client1 2


Actual results:

use-after-free; potential crash of statd


Expected results:

entry is removed from the list


Additional info:

the entry is allocated in nlist_new:

notify_list *
nlist_new(char *my_name, char *mon_name, int state)
{
        notify_list     *new;
 
        new = (notify_list *) xmalloc(sizeof(notify_list));


the entry is freed after nsm_insert_monitored_host() fails:
sm_mon_1_svc(struct mon *argp, struct svc_req *rqstp)
...
        /*
         * Now, Create file on stable storage for host, first deleting any
         * existing records on file.
         */
        nsm_delete_monitored_host(dnsname, mon_name, my_name, 0);
 
        if (!nsm_insert_monitored_host(dnsname,
                                (struct sockaddr *)(char *)&my_addr, argp)) {
                nlist_free(NULL, clnt);
                goto failure;
        }

however, note that an existing entry will not be removed from the list, just freed.


this memory may be accessed again while walking the list:

sm_mon_1_svc(struct mon *argp, struct svc_req *rqstp)
...
        clnt = rtnl;
 
        while ((clnt = nlist_gethost(clnt, mon_name, 0))) {
                if (statd_matchhostname(NL_MY_NAME(clnt), my_name) &&
                    NL_MY_PROC(clnt) == id->my_proc &&
                    NL_MY_PROG(clnt) == id->my_prog &&
                    NL_MY_VERS(clnt) == id->my_vers) {
                        if (memcmp(NL_PRIV(clnt), argp->priv, SM_PRIV_SIZE)) {
Comment 3 Frank Sorenson 2018-09-03 17:32:20 UTC 
Created attachment 1480593 [details]
reproducer for bz1624542

reproducer; requires nsm_client test program from nfs-utils source
Comment 4 Frank Sorenson 2018-09-06 17:50:11 UTC 
committed to upstream nfs-utils

commit 86604e2bd536ea48832dd0bf3d95b15de4de2733 (HEAD -> master, origin/master, origin/HEAD)
Author: Steve Dickson <steved>
Date:   2018-09-06 10:22:11 -0400

    statd: fix use-after-free in monitor list if insertion fails
    
    If nsm_insert_monitored_host() fails while saving the record to
    stable storage, we can't just assume the entry was new. Existing
    records must be removed from the list before being freed.
    
    Reviewed-by: Chuck Lever <chuck.lever>
    Signed-off-by: Frank Sorenson <sorenson>
    Signed-off-by: Steve Dickson <steved>
Comment 10 Yongcheng Yang 2019-04-03 01:32:21 UTC 
Have verified in nfs-utils-1.3.0-0.63.el7
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
https://beaker.engineering.redhat.com/recipes/6693240
-----------------------------------------------------
[08:19:11 root@ ~~]# ./repro.sh
doing initial 'monitor' calls
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.1
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.2
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.3
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.4
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.5
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.6
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.7
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.8
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.9
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.10
SM_MON request successful, state: 3

changing directory ownership to root
attempting to 'monitor' with new cookie
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.10
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.9
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.8
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.7
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.6
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.5
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.4
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.3
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.2
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.1
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.6.redhat.com) to monitor 192.168.123.1
SM_MON request failed, state: -1
rpc.statd is still running
^^^^^^^^^^^^^^^^^^^^^^^^^^^ PASS (Expected 0, got 0)
----------------------------------------------------

Compared with previous nfs-utils-1.3.0-0.61.el7
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
https://beaker.engineering.redhat.com/recipes/6693242
-----------------------------------------------------
[08:38:52 root@ ~~]# ./repro.sh
doing initial 'monitor' calls
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.1
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.2
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.3
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.4
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.5
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.6
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.7
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.8
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.9
SM_MON request successful, state: 3
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.10
SM_MON request successful, state: 3

changing directory ownership to root
attempting to 'monitor' with new cookie
RPC:0
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.10
SM_MON request failed, state: -1
RPC:0
Calling 127.0.0.1 (as rhel-7.7.redhat.com) to monitor 192.168.123.9
sm_mon_1: RPC: Unable to receive; errno = Connection refused
rpc.statd has died
^^^^^^^^^^^^^^^^^^^ FAIL - Should not crash the rpc.statd (Expected 0, got 1)
--------------------------------------------------------------------------

Moving to VERIFIED for now.
Comment 12 errata-xmlrpc 2019-08-06 13:11:50 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/RHBA-2019:2268
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