linux-kernel - Re: [PATCH v2] tracing: Add test for user space strings when filtering on string pointers

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Date:   Fri, 14 Jan 2022 08:29:02 +0100
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     David Laight <David.Laight@...LAB.COM>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pingfan Liu <kernelfans@...il.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>, hca@...ux.ibm.com,
        deller@....de
Subject: Re: [PATCH v2] tracing: Add test for user space strings when
 filtering on  string pointers

Steven Rostedt <rostedt@...dmis.org> writes:

> On Thu, 13 Jan 2022 16:51:15 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
>
>> We could add something later. As it is currently the merge window, and this
>> is a real bug, I'm going to just leave it as is, and we can work to fix the
>> other archs later. I need to get a pull request ready by tomorrow.
>
> Actually I got this working, and looks like a reasonable answer to the
> problem. It basically requires that the user specify that the pointer
> points into user space for the kernel to read it.
>
> Thus instead of:
>
>   echo 'filename ~ "trace"' > events/syscalls/sys_enter_openat/filter
>
> They must now do:
>
>   echo 'filename.ustring ~ "trace"' > events/syscalls/sys_enter_openat/filter
>
> I updated the documentation to reflect this.

Looks good and works on s390, feel free to add my tested-by:

Tested-by: Sven Schnelle <svens@...ux.ibm.com>

Thanks!