Red Hat Bugzilla – Bug 983691
libguestfs double free when kernel link fails during launch
Last modified: 2014-06-17 22:00:21 EDT
+++ This bug was initially created as a clone of Bug #983218 +++
--- Additional comment from Richard W.M. Jones on 2013-07-11 12:25:20 EDT ---
I can see how a double free could occur.
The key observation is the last error message which was captured
in the guestfs handle:
(gdb) print g->last_error
$5 = 0x7f296400c370 "link: /var/tmp/.guestfs-1002/kernel /var/tmp/.guestfs-1002/kernel.29013: Operation not permitted"
This errors occurs in hard_link_to_cached_appliance:
In hard_link_to_cached_appliance, along this error path
params.kernel would be allocated and then free (but not set
back to NULL).
Two levels higher up in the stack, the libvirt backend returns
from guestfs___build_appliance with an error:
and jumps to cleanup: which frees params.kernel again. A
The fix may be to set the kernel pointer to NULL after
freeing it the first time, but I need to systematically
check this code.
--- Additional comment from Richard W.M. Jones on 2013-07-11 12:53:49 EDT ---
Attached is a reproducer (although I think what it may be
reproducing is a related but ever so slightly different
bug in the same area of code).
It requires a working 'sudo' command in order to run
sudo chattr +i /some/temporary/file
Install perl-Sys-Guestfs, download the attached script,
chmod +x the script, and just run it.
If it *segfaults* => bug reproduced.
If it prints "bug 983218 appears to be fixed" => bug fixed.
If it does/prints anything else, result is INVALID. Please
let me know if this happens.
Created attachment 772358 [details]
Updated reproducer script.
Updated reproducer script. Ignore link in previous comment.
Upstream fix is:
Reproduce with libguestfs-1.22.4-1.el7.x86_64 using attached script
[root@intel-5405-32-3 home]# ./test.pl
Segmentation fault (core dumped)
Verified with libguestfs-1.22.6-15.el7
1. Install perl-Sys-Guestfs-1.22.6-15.el7
2. Download test script from Comment 1
3. [lkong@rhel7libguestfs ~]$ sudo ./test.pl
[sudo] password for lkong:
bug 983218 appears to be fixed
(In reply to Lingfei Kong from comment #5)
> 3. [lkong@rhel7libguestfs ~]$ sudo ./test.pl
Note that the test script requires 'sudo'. That doesn't mean
you should run the test script under sudo. Run the
test program as you.
(In reply to Richard W.M. Jones from comment #6)
> Note that the test script requires 'sudo'. That doesn't mean
> you should run the test script under sudo. Run the
> test program as you.
Thanks for your reminding, I read the test script and understand that the test code need 'sudo' permission but not means that I should do the test under "sudo".
This request was resolved in Red Hat Enterprise Linux 7.0.
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