linux-kernel - Re: [PATCH v3 2/3] x86/signal: Rewire the restart

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Message-ID: <20160623212113.GA14180@redhat.com>
Date:	Thu, 23 Jun 2016 23:21:13 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Borislav Petkov <bp@...en8.de>,
	Pedro Alves <palves@...hat.com>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v3 2/3] x86/signal: Rewire the restart_block() syscall
	to have a constant nr

So I think this series is fine, yesterday I misread it completely.

On 06/20, Andy Lutomirski wrote:
>
> Suppose a 64-bit task A traces a 32-bit task B.

And even if they are both 64-bit ...

> B makes a syscall
> that uses ERESTART_RESTARTBLOCK and gets a signal.  A catches
> syscall exit, snapshots B's regs, changes the regs, and resumes.
> Then A restores the snapshot of B's regs.

perhaps in this case gdb should always turn ERESTART_RESTARTBLOCK
into EINTR, because we can't know if B->restart_block is still the
same; it can be changed if the tracee does another RESTARTBLOCK
syscall after the first resume.

But anyway the patch looks good to me.

Oleg.