linux/fs/proc/root.c, branch v3.9

userns: Restrict when proc and sysfs can be mounted

2013-03-27T14:50:08Z

Only allow unprivileged mounts of proc and sysfs if they are already mounted when the user namespace is created. proc and sysfs are interesting because they have content that is per namespace, and so fresh mounts are needed when new namespaces are created while at the same time proc and sysfs have content that is shared between every instance. Respect the policy of who may see the shared content of proc and sysfs by only allowing new mounts if there was an existing mount at the time the user namespace was created. In practice there are only two interesting cases: proc and sysfs are mounted at their usual places, proc and sysfs are not mounted at all (some form of mount namespace jail). Cc: stable@vger.kernel.org Acked-by: Serge Hallyn Signed-off-by: "Eric W. Biederman"

userns: Allow unprivilged mounts of proc and sysfs

2012-11-20T12:19:18Z

- The context in which proc and sysfs are mounted have no effect on the the uid/gid of their files so no conversion is needed except allowing the mount. Acked-by: Serge Hallyn Signed-off-by: "Eric W. Biederman"

pidns: Make the pidns proc mount/umount logic obvious.

2012-11-19T13:59:10Z

Track the number of pids in the proc hash table. When the number of pids goes to 0 schedule work to unmount the kernel mount of proc. Move the mount of proc into alloc_pid when we allocate the pid for init. Remove the surprising calls of pid_ns_release proc in fork and proc_flush_task. Those code paths really shouldn't know about proc namespace implementation details and people have demonstrated several times that finding and understanding those code paths is difficult and non-obvious. Because of the call path detach pid is alwasy called with the rtnl_lock held free_pid is not allowed to sleep, so the work to unmounting proc is moved to a work queue. This has the side benefit of not blocking the entire world waiting for the unnecessary rcu_barrier in deactivate_locked_super. In the process of making the code clear and obvious this fixes a bug reported by Gao feng where we would leak a mount of proc during clone(CLONE_NEWPID|CLONE_NEWNET) if copy_pid_ns succeeded and copy_net_ns failed. Acked-by: "Serge E. Hallyn" Signed-off-by: "Eric W. Biederman"

pidns: Use task_active_pid_ns where appropriate

2012-11-19T13:59:09Z

The expressions tsk->nsproxy->pid_ns and task_active_pid_ns aka ns_of_pid(task_pid(tsk)) should have the same number of cache line misses with the practical difference that ns_of_pid(task_pid(tsk)) is released later in a processes life. Furthermore by using task_active_pid_ns it becomes trivial to write an unshare implementation for the the pid namespace. So I have used task_active_pid_ns everywhere I can. In fork since the pid has not yet been attached to the process I use ns_of_pid, to achieve the same effect. Signed-off-by: Eric W. Biederman

procfs: Don't cache a pid in the root inode.

2012-11-19T11:09:35Z

Now that we have s_fs_info pointing to our pid namespace the original reason for the proc root inode having a struct pid is gone. Caching a pid in the root inode has led to some complicated code. Now that we don't need the struct pid, just remove it. Signed-off-by: Eric W. Biederman

procfs: Use the proc generic infrastructure for proc/self.

2012-11-19T11:09:34Z

I had visions at one point of splitting proc into two filesystems. If that had happened proc/self being the the part of proc that actually deals with pids would have been a nice cleanup. As it is proc/self requires a lot of unnecessary infrastructure for a single file. The only user visible change is that a mounted /proc for a pid namespace that is dead now shows a broken proc symlink, instead of being completely invisible. I don't think anyone will notice or care. Signed-off-by: Eric W. Biederman

fs/proc/root.c: use NULL instead of 0 for pointer

2012-10-05T18:05:19Z

This cleanup also fixes the following sparse warning: fs/proc/root.c:64:45: warning: Using plain integer as NULL pointer Signed-off-by: Sachin Kamat Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

VFS: Pass mount flags to sget()

2012-07-14T12:38:34Z

Pass mount flags to sget() so that it can use them in initialising a new superblock before the set function is called. They could also be passed to the compare function. Signed-off-by: David Howells Signed-off-by: Al Viro

stop passing nameidata to ->lookup()

2012-07-14T12:34:32Z

Just the flags; only NFS cares even about that, but there are legitimate uses for such argument. And getting rid of that completely would require splitting ->lookup() into a couple of methods (at least), so let's leave that alone for now... Signed-off-by: Al Viro

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2012-05-24T00:42:39Z

Pull user namespace enhancements from Eric Biederman: "This is a course correction for the user namespace, so that we can reach an inexpensive, maintainable, and reasonably complete implementation. Highlights: - Config guards make it impossible to enable the user namespace and code that has not been converted to be user namespace safe. - Use of the new kuid_t type ensures the if you somehow get past the config guards the kernel will encounter type errors if you enable user namespaces and attempt to compile in code whose permission checks have not been updated to be user namespace safe. - All uids from child user namespaces are mapped into the initial user namespace before they are processed. Removing the need to add an additional check to see if the user namespace of the compared uids remains the same. - With the user namespaces compiled out the performance is as good or better than it is today. - For most operations absolutely nothing changes performance or operationally with the user namespace enabled. - The worst case performance I could come up with was timing 1 billion cache cold stat operations with the user namespace code enabled. This went from 156s to 164s on my laptop (or 156ns to 164ns per stat operation). - (uid_t)-1 and (gid_t)-1 are reserved as an internal error value. Most uid/gid setting system calls treat these value specially anyway so attempting to use -1 as a uid would likely cause entertaining failures in userspace. - If setuid is called with a uid that can not be mapped setuid fails. I have looked at sendmail, login, ssh and every other program I could think of that would call setuid and they all check for and handle the case where setuid fails. - If stat or a similar system call is called from a context in which we can not map a uid we lie and return overflowuid. The LFS experience suggests not lying and returning an error code might be better, but the historical precedent with uids is different and I can not think of anything that would break by lying about a uid we can't map. - Capabilities are localized to the current user namespace making it safe to give the initial user in a user namespace all capabilities. My git tree covers all of the modifications needed to convert the core kernel and enough changes to make a system bootable to runlevel 1." Fix up trivial conflicts due to nearby independent changes in fs/stat.c * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (46 commits) userns: Silence silly gcc warning. cred: use correct cred accessor with regards to rcu read lock userns: Convert the move_pages, and migrate_pages permission checks to use uid_eq userns: Convert cgroup permission checks to use uid_eq userns: Convert tmpfs to use kuid and kgid where appropriate userns: Convert sysfs to use kgid/kuid where appropriate userns: Convert sysctl permission checks to use kuid and kgids. userns: Convert proc to use kuid/kgid where appropriate userns: Convert ext4 to user kuid/kgid where appropriate userns: Convert ext3 to use kuid/kgid where appropriate userns: Convert ext2 to use kuid/kgid where appropriate. userns: Convert devpts to use kuid/kgid where appropriate userns: Convert binary formats to use kuid/kgid where appropriate userns: Add negative depends on entries to avoid building code that is userns unsafe userns: signal remove unnecessary map_cred_ns userns: Teach inode_capable to understand inodes whose uids map to other namespaces. userns: Fail exec for suid and sgid binaries with ids outside our user namespace. userns: Convert stat to return values mapped from kuids and kgids userns: Convert user specfied uids and gids in chown into kuids and kgid userns: Use uid_eq gid_eq helpers when comparing kuids and kgids in the vfs ...