linux-kernel - Re: [PATCH v6 1/2] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

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Date:   Thu, 26 Jan 2023 01:30:08 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Gregory Price <gourry.memverge@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        avagin@...il.com, peterz@...radead.org, luto@...nel.org,
        krisman@...labora.com, tglx@...utronix.de, corbet@....net,
        shuah@...nel.org, Gregory Price <gregory.price@...verge.com>
Subject: Re: [PATCH v6 1/2] ptrace,syscall_user_dispatch: Implement Syscall
 User Dispatch Suspension

On 01/24, Gregory Price wrote:
>
> Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and
> modify Syscall User Dispatch to suspend interception when enabled.
>
> This is modeled after the SUSPEND_SECCOMP feature, which suspends
> SECCOMP interposition.  Without doing this, software like CRIU will
> inject system calls into a process and be intercepted by Syscall
> User Dispatch, either causing a crash (due to blocked signals) or
> the delivery of those signals to a ptracer (not the intended behavior).

Cough... Gregory, I am sorry ;)

but can't we drop this patch to ?

CRIU needs to do PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG and check
config->mode anyway as we discussed.

Then it can simply set *config->selector = SYSCALL_DISPATCH_FILTER_ALLOW
with the same effect, no?

Oleg.