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This bug is created as a clone of upstream ticket:
https://fedorahosted.org/sssd/ticket/2405
We have a use-after-free situation in the dyndns code, found by Chris Hartman and reported on sssd-users:
{{{
==13038== 1 errors in context 9 of 14:
==13038== Invalid read of size 1
==13038== at 0x807C747: resolv_get_string_ptr_address (async_resolv.c:1442)
==13038== by 0x8069777: be_nsupdate_create_ptr_msg (dp_dyndns.c:366)
==13038== by 0x54F824E: sdap_dyndns_update_ptr_step (sdap_dyndns.c:402)
==13038== by 0x54F8663: sdap_dyndns_update_done (sdap_dyndns.c:378)
==13038== by 0x4051D7A: _tevent_req_notify_callback (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x4051DB9: _tevent_req_done (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x8067CF3: be_nsupdate_done (dp_dyndns.c:1093)
==13038== by 0x4051D7A: _tevent_req_notify_callback (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x4051DB9: _tevent_req_done (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x8068347: nsupdate_child_handler (dp_dyndns.c:915)
==13038== by 0x4197163: child_invoke_callback (child_common.c:603)
==13038== by 0x4051577: tevent_common_loop_immediate (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== Address 0x6b086af is 55 bytes inside a block of size 176 free'd
==13038== at 0x402B3D8: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==13038== by 0x40622B2: ??? (in /usr/lib/i386-linux-gnu/libtalloc.so.2.1.0)
==13038== by 0x406223E: ??? (in /usr/lib/i386-linux-gnu/libtalloc.so.2.1.0)
==13038== by 0x406223E: ??? (in /usr/lib/i386-linux-gnu/libtalloc.so.2.1.0)
==13038== by 0x405EA0E: _talloc_free (in /usr/lib/i386-linux-gnu/libtalloc.so.2.1.0)
==13038== by 0x54F7101: sdap_dyndns_dns_addrs_done (sdap_dyndns.c:207)
==13038== by 0x4051D7A: _tevent_req_notify_callback (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x4051DB9: _tevent_req_done (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x8067483: nsupdate_get_addrs_done (dp_dyndns.c:726)
==13038== by 0x4051D7A: _tevent_req_notify_callback (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x4051DB9: _tevent_req_done (in /usr/lib/i386-linux-gnu/libtevent.so.0.9.19)
==13038== by 0x807A079: resolv_gethostbyname_done (async_resolv.c:1367)
==13038==
==13038==
}}}
The crash can be reproduced if ip addresses are obtained from network interface
e.g.
dyndns_iface = eth0
and an interface should have assigned at least two IP addresses (IPv4, IPv6)
It needn't crash every time; therefore it is better to export environment variable TALLOC_FREE_FILL
man talloc says:
If TALLOC_FREE_FILL environment variable is set, the memory occupied by
the context is filled with the value of this variable; when memory is
freed. The value should be a numeric representation of the character
you want to use.
For example:
echo "TALLOC_FREE_FILL=253" >> /etc/sysconfig/sssd
Environment variables from file /etc/sysconfig/sssd are used also on rhel7,
because sssd.service file contains option EnvironmentFile option in Service section
bash-4.2# grep -C1 EnvironmentFile /usr/lib/systemd/system/sssd.service
[Service]
EnvironmentFile=-/etc/sysconfig/sssd
ExecStart=/usr/sbin/sssd -D -f
Unable to reproduce the bug using sssd-1.11.6-28.el6.x86_64 on RHEL6. Followed the steps adding TALLOC_FREE_FILL=253 to /etc/sysconfig/sssd and environment variable on a host with two interfaces, eth0:ipv4:ipv6.
Marking this fix as verified.
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/RHBA-2014-1375.html