• Davidlohr Bueso's avatar
    ipc/msg: introduce msgctl(MSG_STAT_ANY) · 23c8cec8
    Davidlohr Bueso authored
    There is a permission discrepancy when consulting msq ipc object
    metadata between /proc/sysvipc/msg (0444) and the MSG_STAT shmctl
    command.  The later does permission checks for the object vs S_IRUGO.
    As such there can be cases where EACCESS is returned via syscall but the
    info is displayed anyways in the procfs files.
    
    While this might have security implications via info leaking (albeit no
    writing to the msq metadata), this behavior goes way back and showing
    all the objects regardless of the permissions was most likely an
    overlook - so we are stuck with it.  Furthermore, modifying either the
    syscall or the procfs file can cause userspace programs to break (ie
    ipcs).  Some applications require getting the procfs info (without root
    privileges) and can be rather slow in comparison with a syscall -- up to
    500x in some reported cases for shm.
    
    This patch introduces a new MSG_STAT_ANY command such that the msq ipc
    object permissions are ignored, and only audited instead.  In addition,
    I've left the lsm security hook checks in place, as if some policy can
    block the call, then the user has no other choice than just parsing the
    procfs file.
    
    Link: http://lkml.kernel.org/r/20180215162458.10059-4-dave@stgolabs.netSigned-off-by: 's avatarDavidlohr Bueso <dbueso@suse.de>
    Reported-by: 's avatarRobert Kettler <robert.kettler@outlook.com>
    Cc: Eric W. Biederman <ebiederm@xmission.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Manfred Spraul <manfred@colorfullife.com>
    Cc: Michael Kerrisk <mtk.manpages@gmail.com>
    Cc: Michal Hocko <mhocko@kernel.org>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    23c8cec8
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