• Linus Torvalds's avatar
    Sanitize 'move_pages()' permission checks · 61332dc5
    Linus Torvalds authored
    commit 197e7e52 upstream.
    
    The 'move_paghes()' system call was introduced long long ago with the
    same permission checks as for sending a signal (except using
    CAP_SYS_NICE instead of CAP_SYS_KILL for the overriding capability).
    
    That turns out to not be a great choice - while the system call really
    only moves physical page allocations around (and you need other
    capabilities to do a lot of it), you can check the return value to map
    out some the virtual address choices and defeat ASLR of a binary that
    still shares your uid.
    
    So change the access checks to the more common 'ptrace_may_access()'
    model instead.
    
    This tightens the access checks for the uid, and also effectively
    changes the CAP_SYS_NICE check to CAP_SYS_PTRACE, but it's unlikely that
    anybody really _uses_ this legacy system call any more (we hav ebetter
    NUMA placement models these days), so I expect nobody to notice.
    
    Famous last words.
    Reported-by: 's avatarOtto Ebeling <otto.ebeling@iki.fi>
    Acked-by: 's avatarEric W. Biederman <ebiederm@xmission.com>
    Cc: Willy Tarreau <w@1wt.eu>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    61332dc5