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Date:   Wed, 20 Mar 2019 14:27:32 +0100
From:   Oleg Nesterov <oleg@redhat.com>
To:     Andrei Vagin <avagin@gmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [RESEND PATCH] ptrace: take into account saved_sigmask in
 PTRACE_{GET,SET}SIGMASK
Message-ID: <20190320132731.GC21673@redhat.com>
References: <20190319191957.27156-1-avagin@gmail.com>
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On 03/19, Andrei Vagin wrote:
>
> There are a few system calls (pselect, ppoll, etc) which replace a task
> sigmask while they are running in a kernel-space
>
> When a task calls one of these syscalls, the kernel saves a current
> sigmask in task->saved_sigmask and sets a syscall sigmask.
>
> On syscall-exit-stop, ptrace traps a task before restoring the
> saved_sigmask, so PTRACE_GETSIGMASK returns the syscall sigmask and
> PTRACE_SETSIGMASK does nothing, because its sigmask is replaced by
> saved_sigmask, when the task returns to user-space.
>
> This patch fixes this problem.  PTRACE_GET_SIGMASK returns saved_sigmask
> is it's set.  PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.

Acked-by: Oleg Nesterov <oleg@redhat.com>