• Mark Rutland's avatar
    ARM: 8692/1: mm: abort uaccess retries upon fatal signal · 746a272e
    Mark Rutland authored
    
    
    When there's a fatal signal pending, arm's do_page_fault()
    implementation returns 0. The intent is that we'll return to the
    faulting userspace instruction, delivering the signal on the way.
    
    However, if we take a fatal signal during fixing up a uaccess, this
    results in a return to the faulting kernel instruction, which will be
    instantly retried, resulting in the same fault being taken forever. As
    the task never reaches userspace, the signal is not delivered, and the
    task is left unkillable. While the task is stuck in this state, it can
    inhibit the forward progress of the system.
    
    To avoid this, we must ensure that when a fatal signal is pending, we
    apply any necessary fixup for a faulting kernel instruction. Thus we
    will return to an error path, and it is up to that code to make forward
    progress towards delivering the fatal signal.
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Reviewed-by: default avatarSteve Capper <steve.capper@arm.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
    746a272e
fault.c 14.9 KB