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Cause:
If client_migrate_info was called once with
cert-host-subject and then again without
cert-host-subject, on a third call to
client_migrate info, the cert-host-subject from the first
call would have been freed for the second time.
[ An even more detailed explanation:
In the first call with cert-host-subject a pointer was
allocated.
In the second call without cert-host-subject the pointer
was freed, but not set to NULL.
In the third call that same pointer was freed again.
]
Consequence:
glibc complains about double free and later it causes
a segmentation fault.
Fix:
Set the pointer to NULL, if cert-host-subject is not given.
[ That's fix happens in the "second" migrate-info ]
Result:
The pointer is freed only once and qemu-kvm/spice-server does not crash.
Created attachment 614861[details]
qemu backtrace
Description of problem:
repeated client_migrate_info caused freeing invalid pointer, followed ultimately by segfault in _int_malloc.
The freeing of invalid pointer seems to be quite common (I see it second time in fairly short time frame) but the segmentation fault happened to me for the first time.
Version-Release number of selected component (if applicable):
qemu-kvm-0.12.1.2-2.312.el6.x86_64
spice-server-0.11.3-1_test2.el6.x86_64
How reproducible:
didn't try to reproduce
Steps to Reproduce:
0. have a set of x509 certs/keys in /etc/pki/libvirt-spice
1. run source qemu: qemu-kvm -monitor stdio -spice addr=::,tls-port=5811,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on,disable-ticketing
2. run dest qemu: qemu-kvm -monitor stdio -spice addr=::,tls-port=5813,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on,disable-ticketing -incoming tcp::5712
3. connect with client: remote-viewer --spice-ca-file /etc/pki/libvirt-spice/ca-cert.pem spice://<hostame>/?tls-port=5811
NOTE: <hostname> must match CN in Subject of ${x509-dir}/server-cert.pem
4. issue repeatedly this command on qemu CLI: client_migrate_info spice 127.0.0.1 0 5813 <Subject_of_server-cert.pem>
note: you may try without host subject specified as well
Actual results:
after several cycles, freeing invalid pointers appear:
*** glibc detected *** qemu-kvm: free(): invalid pointer: 0x00007f6a0e43a710 ***
after several more cycles, full segmentation fault occurs
Expected results:
qemu will never segfault
Additional info:
When I tried to run source qemu in valgrind:
valgrind -v --error-limit=no --tool=memcheck --track-origins=yes --leak-check=full qemu-kvm -monitor stdio -spice addr=::,tls-port=5811,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on,disable-ticketing
it got crazy as soon as I connected to it, repeating this stuff over an over (even when I rerun it with plaintext-port only and no x509-dir):
==23650== Use of uninitialised value of size 8
==23650== at 0x9970C20: bn_mul_mont (x86_64-mont.s:152)
==23650== by 0x152F1A6801292306: ???
==23650== by 0x8CD975FE1C327A67: ???
==23650== by 0xD0E8B5EB10CDE393: ???
==23650== by 0xEF2A0D7A89142F69: ???
==23650== by 0x1800C336037BE0BF: ???
==23650== by 0xF933698707AE7DBD: ???
==23650== by 0x8F86049E00EC185C: ???
==23650== by 0x644D9C308B6DECCD: ???
==23650== Uninitialised value was created by a heap allocation
==23650== at 0x4A05FDE: malloc (vg_replace_malloc.c:236)
==23650== by 0x993995D: CRYPTO_malloc (mem.c:306)
==23650== by 0x996BDDD: bnrand (bn_rand.c:134)
==23650== by 0x996BC47: bn_rand_range (bn_rand.c:281)
==23650== by 0x996EC3A: BN_is_prime_fasttest_ex (bn_prime.c:322)
==23650== by 0x996F203: BN_generate_prime_ex (bn_prime.c:199)
==23650== by 0x997854A: RSA_generate_key_ex (rsa_gen.c:213)
==23650== by 0x657C587: reds_handle_read_link_done (reds.c:1539)
==23650== by 0x6577D75: spice_server_add_client (reds.c:3035)
==23650== by 0x6577DD9: reds_accept (reds.c:3012)
==23650== by 0x16B06E: main_loop_wait (vl.c:3999)
==23650== by 0x18C9A9: kvm_main_loop (qemu-kvm.c:2244)
qemu just passes on the info to spice server, reassigning.
Comment 4RHEL Program Management
2012-12-14 08:01:14 UTC
This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.
Hi,
Is it possible that you called client_migrate_info once with <host-subject> and then at a following call you (maybe accidently) omitted the <host-subject> and then the following call crashed?
I posted a patch for the above bug http://patchwork.freedesktop.org/patch/13728/
Please let me know if you manage to reproduce the bug without omitting the host-subject.
(In reply to Yonit Halperin from comment #6)
> Hi,
>
> Is it possible that you called client_migrate_info once with <host-subject>
> and then at a following call you (maybe accidently) omitted the
> <host-subject> and then the following call crashed?
>
> I posted a patch for the above bug
> http://patchwork.freedesktop.org/patch/13728/
>
> Please let me know if you manage to reproduce the bug without omitting the
> host-subject.
Yes, IIRC it was this case.
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-2013-1571.html
Created attachment 614861 [details] qemu backtrace Description of problem: repeated client_migrate_info caused freeing invalid pointer, followed ultimately by segfault in _int_malloc. The freeing of invalid pointer seems to be quite common (I see it second time in fairly short time frame) but the segmentation fault happened to me for the first time. Version-Release number of selected component (if applicable): qemu-kvm-0.12.1.2-2.312.el6.x86_64 spice-server-0.11.3-1_test2.el6.x86_64 How reproducible: didn't try to reproduce Steps to Reproduce: 0. have a set of x509 certs/keys in /etc/pki/libvirt-spice 1. run source qemu: qemu-kvm -monitor stdio -spice addr=::,tls-port=5811,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on,disable-ticketing 2. run dest qemu: qemu-kvm -monitor stdio -spice addr=::,tls-port=5813,x509-dir=/etc/pki/libvirt-spice,seamless-migration=on,disable-ticketing -incoming tcp::5712 3. connect with client: remote-viewer --spice-ca-file /etc/pki/libvirt-spice/ca-cert.pem spice://<hostame>/?tls-port=5811 NOTE: <hostname> must match CN in Subject of ${x509-dir}/server-cert.pem 4. issue repeatedly this command on qemu CLI: client_migrate_info spice 127.0.0.1 0 5813 <Subject_of_server-cert.pem> note: you may try without host subject specified as well Actual results: after several cycles, freeing invalid pointers appear: *** glibc detected *** qemu-kvm: free(): invalid pointer: 0x00007f6a0e43a710 *** after several more cycles, full segmentation fault occurs Expected results: qemu will never segfault Additional info: