• Linus Torvalds's avatar
    Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace · 644473e9
    Linus Torvalds authored
    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
       - 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
stat.c 11 KB