Re: [PATCH 0/3] signal: requeuing undeliverable signals

From: Eric W. Biederman
Date: Wed Nov 17 2021 - 11:51:17 EST

Kyle Huey <me@xxxxxxxxxxxx> writes:

> On Mon, Nov 15, 2021 at 9:31 PM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:
>> Kyle Huey recently reported[1] that rr gets confused if SIGKILL prevents
>> ptrace_signal from delivering a signal, as the kernel setups up a signal
>> frame for a signal that rr did not have a chance to observe with ptrace.
>> In looking into it I found a couple of bugs and a quality of
>> implementation issue.
>> - The test for signal_group_exit should be inside the for loop in get_signal.
>> - Signals should be requeued on the same queue they were dequeued from.
>> - When a fatal signal is pending ptrace_signal should not return another
>> signal for delivery.
>> Kyle Huey has verified[2] an earlier version of this change.
>> I have reworked things one more time to completely fix the issues
>> raised, and to keep the code maintainable long term.
>> I have smoke tested this code and combined with a careful review I
>> expect this code to work fine. Kyle if you can double check that
>> my last round of changes still works for rr I would appreciate it.
> This still fixes the race we reported.

> Tested-by: Kyle Huey <khuey@xxxxxxxxxxxx>

Thank you very much for retesting.