94ac69c182
CVE-2020-14339 When building domain's private /dev in a namespace, libdevmapper is consulted for getting full dependency tree of domain's disks. The reason is that for a multipath devices all dependent devices must be created in the namespace and allowed in CGroups. However, this approach is very fragile as building of namespace happens in the forked off child process, after mass close of FDs and just before dropping privileges and execing QEMU. And it so happens that when calling libdevmapper APIs, one of them opens /dev/mapper/control and saves the FD into a global variable. The FD is kept open until the lib is unlinked or dm_lib_release() is called explicitly. We are doing neither. However, the virDevMapperGetTargets() function is called also from libvirtd (when setting up CGroups) and thus has to be thread safe. Unfortunately, libdevmapper APIs are not thread safe (nor async signal safe) and thus we can't use them. Reimplement what libdevmapper would do using plain C (ioctl()-s, /proc/devices parsing, /dev/mapper dirwalking, and so on). Fixes: a30078cb832646177defd256e77c632905f1e6d0 Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1858260 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> cherry-pick from commit 22494556542c676d1b9e7f1c1f2ea13ac17e1e3e Signed-off-by: Jiajie Li <lijiajie11@huawei.com>