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Date:   Thu, 6 Jun 2019 13:05:22 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     David Laight <David.Laight@ACULAB.COM>
Cc:     'Linus Torvalds' <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Deepa Dinamani <deepa.kernel@gmail.com>,
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        stable <stable@vger.kernel.org>,
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Subject: Re: [PATCH -mm 0/1] signal: simplify
 set_user_sigmask/restore_user_sigmask
Message-ID: <20190606110522.GA4691@redhat.com>
References: <20190522032144.10995-1-deepa.kernel@gmail.com>
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 <20190604134117.GA29963@redhat.com>
 <20190605155801.GA25165@redhat.com>
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On 06/06, David Laight wrote:
>
> If a signal handler is called, I presume that the trampoline
> calls back into the kernel to get further handlers called
> and to finally restore the original signal mask?

See sigmask_to_save(), this is what the kernel records in uc.uc_sigmask
before the signal handler runs, after that current->saved_sigmask has no
meaning.

When signal handler returns it does sys_rt_sigreturn() which restores
the original mask saved in uc_sigmask.

> What happens if a signal handler calls something that
> would normally write to current->saved_sigmask?

See above.

Oleg.