On Tue, Jul 02, 2013 at 10:56:37AM +0200, Richard Weinberger wrote: > Am 02.07.2013 10:44, schrieb Eric W. Biederman: > > Gao feng <gaofeng@xxxxxxxxxxxxxx> writes: > > > >> On 07/02/2013 12:16 AM, Daniel P. Berrange wrote: > >>> I'm struggling debugging a strange problem with interaction between user > >>> namespaces, cap_set and ownership of files in /proc/1/ > >>> > >> > >> This problem is occured after we call setuid/gid. > >> > >> for example, a task whose pid is 1234 calls > >> setregid(10,10); > >> setreuid(10,10); If seems to get reset to the right values (0:0) when we execve() the init binary though. This doesn't happen if we have invoked the capset() syscall in between the setregid & the execve() calls. > >> > >> > >> The uid/gid of the /proc/1234 is 10:0 > >> ll /proc/1234 -d > >> dr-xr-xr-x 8 uucp wheel 0 Jul 2 10:57 /proc/1234 > >> > >> the uid/gid of the files under /proc/1234 are two kinds... > >> ll /proc/1234 > >> dr-xr-xr-x 2 uucp wheel 0 Jul 2 10:58 attr > >> -rw-r--r-- 1 root root 0 Jul 2 10:58 autogroup > >> ... > >> dr-xr-xr-x 5 uucp wheel 0 Jul 2 10:58 net > >> dr-x--x--x 2 root root 0 Jul 2 10:58 ns > >> ... > >> dr-xr-xr-x 3 uucp wheel 0 Jul 2 10:58 task > >> > >> I checked the pre_revalidate and found the owner of the files under /proc/<pid> > >> will be set to the GLOBAL_ROOT_UID if the task executed setuid/setgid(task_dumpable is false). > >> Is this what we expected? why? > > > > Expected yes. Perfect perhaps not. > > > > That piece of code has not been examined to see if it is safe to use > > make_kuid(task_user_ns(task), 0), instead of GLOBAL_ROOT_UID. > > > >> For user namespace,the owner of /proc/1/* is incorrect and > >> after task call setuid/gid in user namespace, the owner of /proc/<pid-of-this-task>/* is incorrect > >> too. > > > > From the current semantics of dumpable GLOBAL_ROOT_UID is correct. > > > > Please double check but I believe /proc/self should continue to work, > > despite this. > > /proc/self is not an option. systemd (in particular some of it's tools with pid != 1) read from /proc/1/environ to find out > what environment variables it got to detect LXC and other visualization environments. > With userns enabled this check fails and systemd goes nuts because it thinks that it lives on top of a "real" Linux. I don't even see how /proc/self would solve this, since it is just a symlink pointing to /proc/1 in this scenario, so the ownership of files at /proc/1/XXXX would still be wrong. This isn't really a systemd specific problem either, I think any app would expect to be able to read its own files under /proc/$PID/ Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
