• Al Viro's avatar
    aio_run_iocb(): kill dead check · 47e39362
    Al Viro authored
    
    
    We check if ->ki_pos is positive.  However, by that point we have
    already done rw_verify_area(), which would have rejected such
    unless the file had been one of /dev/mem, /dev/kmem and /proc/kcore.
    All of which do not have vectored rw methods, so we would've bailed
    out even earlier.
    
    This check had been introduced before rw_verify_area() had been added there
    - in fact, it was a subset of checks done on sync paths by rw_verify_area()
    (back then the /dev/mem exception didn't exist at all).  The rest of checks
    (mandatory locking, etc.) hadn't been added until later.  Unfortunately,
    by the time the call of rw_verify_area() got added, the /dev/mem exception
    had already appeared, so it wasn't obvious that the older explicit check
    downstream had become dead code.  It *is* a dead code, though, since the few
    files for which the exception applies do not have ->aio_{read,write}() or
    ->{read,write}_iter() and for them we won't reach that check anyway.
    
    What's more, even if we ever introduce vectored methods for /dev/mem
    and friends, they'll have to cope with negative positions anyway, since
    readv(2) and writev(2) are using the same checks as read(2) and write(2) -
    i.e. rw_verify_area().
    
    Let's bury it.
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    47e39362