Jann,
Thanks for the feedback. I will post a revised patch shortly.
On the related topic of "pdeath_signal", there are several inconsistencies
by preserving the flag across execve(2). The flag is cleared under several
conditions in different places. I will start a separate thread to see if
it can still be cleaned up.
PR_SET_PDEATHSIG (since Linux 2.1.57)
Set the parent death signal of the calling process to arg2
(either a signal value in the range 1..maxsig, or 0 to clear).
This is the signal that the calling process will get when its
parent dies. This value is cleared for the child of a fork(2)
and (since Linux 2.4.36 / 2.6.23) when executing a set-user-ID
or set-group-ID binary, or a binary that has associated
capabilities (see capabilities(7)). This value is preserved
across execve(2).
-- Enke
On 10/22/18 8:40 AM, Jann Horn wrote:
> On Sat, Oct 20, 2018 at 1:01 AM Enke Chen <enkechen@xxxxxxxxx> wrote:
>> Regarding the security considerations, it seems simpler and more secure to
>> just clear the "pre-coredump signal" cross execve(2), and let the new program
>> decide for itself. What do you think?
>
> I don't have a problem with these semantics.
>
> I could imagine someone being unhappy about the theoretical race
> window if they want to perform an in-place reexecution of a running
> service, but I don't know whether anyone actually cares about that.
>
>> Changes to prctl(2):
>>
>> DESCRIPTION
>>
>> PR_SET_PREDUMP_SIG (since Linux 4.20.x)
>> This allows the calling process to receive a signal (arg2,
>> if nonzero) from a child process prior to the coredump of
>> the child process. arg2 must be SIGUSR1, or SIGUSR2, or
>> SIGCHLD, or 0 (for clear).
>>
>> When SIGCHLD is specified, the signal code is set to
>> CLD_PREDUMP in such an SIGCHLD signal.
>>
>> The value of the pre-coredump signal is cleared across
>> execve(2), or for the child of a fork(2).
>>
>> PR_GET_PREDUMP_SIG (since Linux 4.20.x)
>> Return the current value of the pre-coredump signal for the
>> calling process, in the location pointed to by (int *) arg2.
