linux-kernel - Re: [PATCH] ptrace: take into account saved_sigmask in PTRACE

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Message-ID: <20181127162326.GB13284@redhat.com>
Date:   Tue, 27 Nov 2018 17:23:27 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrei Vagin <avagin@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] ptrace: take into account saved_sigmask in
 PTRACE_{GET,SET}SIGMASK

On 11/26, Andrei Vagin wrote:
>
> > IOW, could you please explain how PTRACE_SETSIGMASK should be used, and why
> > it doesn't do something like
> >
>
> CRIU uses PTRACE_SETSIGMASK when it injects a parasite code into a
> target process. In this case, we have to be sure that when the process
> is resumed by PTRACE_CONT, it will not start handling signals and
> executing signal handlers.

So iiuc CRUI uses PTRACE_SETSIGMASK to block all signals, run the parasite
code, then restore the original sigmask.

Assuming that CRIU also turns ERESTARTNOHAND into syscall-restart (I think
it does ;) everything looks correct...

OK, I think the patch is fine.

Oleg.