linux-kernel - Re: [PATCH v3] tracing: Have format file honor EVENT_FILE_FL

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Message-ID: <b14bdf3a-b24c-4765-b3e0-971880e40fb0@grsecurity.net>
Date: Tue, 30 Jul 2024 22:40:21 +0200
From: Mathias Krause <minipli@...ecurity.net>
To: Steven Rostedt <rostedt@...dmis.org>, LKML
 <linux-kernel@...r.kernel.org>,
 Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Ajay Kaher <ajay.kaher@...adcom.com>, Ilkka Naulapää
 <digirigawa@...il.com>, Linus Torvalds <torvalds@...ux-foundation.org>,
 Al Viro <viro@...iv.linux.org.uk>, regressions@...mhuis.info,
 Dan Carpenter <dan.carpenter@...aro.org>,
 Beau Belgrave <beaub@...ux.microsoft.com>,
 Florian Fainelli <florian.fainelli@...adcom.com>,
 Alexey Makhalov <alexey.makhalov@...adcom.com>,
 Vasavi Sirnapalli <vasavi.sirnapalli@...adcom.com>
Subject: Re: [PATCH v3] tracing: Have format file honor EVENT_FILE_FL_FREED


On 30.07.24 17:15, Steven Rostedt wrote:
> On Tue, 30 Jul 2024 11:06:57 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
>> Link: https://lore.kernel.org/all/20240719204701.1605950-1-minipli@grsecurity.net/
>>
>> Cc: stable@...r.kernel.org
>> Fixes: b63db58e2fa5d ("eventfs/tracing: Add callback for release of an eventfs_inode")
>> Reported-by: Mathias Krause <minipli@...ecurity.net>
>> Tested-by: Mathias Krause <minipli@...ecurity.net>
> 
> Hi Mathias,
> 
> I kept your "Tested-by" tag because you did test the part that fixes the
> bug you reported. I just added on top of that one to handle other possibly
> cases. Let me know if you want me to drop that tag, or if you tested this
> version as well.

Hi Steven,

I retested this version and it's still fixing the bug, so you can keep
the "Tested-by" tag.

Also nice catch with covering the write part of "filter" as well!
Testing this specifically, I saw a few ENODEV's, so it's definitely
possible to hit this one as well.

Thanks,
Mathias

> 
> Thanks,
> 
> -- Steve
> 
> 
>> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
>> ---
>> Changes since v3: https://lore.kernel.org/20240726132811.306a449e@rorschach.local.home
>>
>> - After inspecting the code, there's several users of event_file_data()
>>   that return the trace_event_file descriptor when it could be set to be
>>   freed. Add a new helper function: event_file_file() that will make sure
>>   the event_mutex is held and check the flag and return NULL if the file is
>>   freed.