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d51023d4c2
Latent bug introduced in commit2d6a581960(Aug 2009), but not exposed until commit1859939a(Jan 2011). Basically, when virExec creates a pipe, it always marks libvirt's side as cloexec. If libvirt then wants to hand that pipe to another child process, things work great if the fd is dup2()'d onto stdin or stdout (as with stdin: or exec: migration), but if the pipe is instead used as-is (such as with fd: migration) then qemu sees EBADF because the fd was closed at exec(). This is a minimal fix for the problem at hand; it is slightly racy, but no more racy than the rest of libvirt fd handling, including the case of uncompressed save images. A more invasive fix, but ultimately safer at avoiding leaking unintended fds, would be to _always and atomically_ open all fds as cloexec in libvirt (thanks to primitives like open(O_CLOEXEC), pipe2(), accept4(), ...), then teach virExec to clear that bit for all fds explicitly marked to be handed to the child only after forking. * src/qemu/qemu_command.c (qemuBuildCommandLine): Clear cloexec flag. * tests/qemuxml2argvtest.c (testCompareXMLToArgvFiles): Tweak test.
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>