A flaw was reported [1] in Xen version 4.1 and later:
If xc_cpumap_alloc() fails then xc_cpupool_getinfo() will free and incorrectly
return the then-free pointer to the result structure.
An attacker may be able to cause a multi-threaded toolstack using this
function to race against itself leading to heap corruption and a
potential DoS.
Depending on the malloc implementation, privilege escalation cannot be
ruled out.
The flaw is present in Xen 4.1 onwards. Only multithreaded toolstacks
are vulnerable. Only systems where management functions (such as
domain creation) are exposed to untrusted users are vulnerable.
xl is not multithreaded, so is not vulnerable. However, multithreaded
toolstacks using libxl as a library are vulnerable. xend is
vulnerable.
[1] http://xenbits.xenproject.org/xsa/advisory-88.html
Acknowledgements:
Red Hat would like to thank the Xen project for reporting this issue.
Statement:
Not vulnerable. This issue did not affect the versions of the kernel-xen package as shipped with Red Hat Enterprise Linux 5.
This issue did not affect Red Hat Enterprise Linux 6 and Red Hat Enterprise MRG 2 as we did not have support for Xen hypervisor.