linux-kernel - Re: [PATCH] tracing: Fix race where eprobes can be called before the event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 18 Nov 2022 21:18:09 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Rafael Mendonca <rafaelmendsr@...il.com>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH] tracing: Fix race where eprobes can be called before
 the event

On Thu, 17 Nov 2022 21:42:49 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> The flag that tells the event to call its triggers after reading the event
> is set for eprobes after the eprobe is enabled. This leads to a race where
> the eprobe may be triggered at the beginning of the event where the record
> information is NULL. The eprobe then dereferences the NULL record causing
> a NULL kernel pointer bug.
> 
> Test for a NULL record to keep this from happening.
> 
> Link: https://lore.kernel.org/linux-trace-kernel/20221116192552.1066630-1-rafaelmendsr@gmail.com/

This looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

BTW, would other trigger callbacks also need to add similar checks?

Thank you,

> 
> Cc: stable@...r.kernel.org
> Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
> Reported-by: Rafael Mendonca <rafaelmendsr@...il.com>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  kernel/trace/trace_eprobe.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> index 5dd0617e5df6..6b31b74954d9 100644
> --- a/kernel/trace/trace_eprobe.c
> +++ b/kernel/trace/trace_eprobe.c
> @@ -563,6 +563,9 @@ static void eprobe_trigger_func(struct event_trigger_data *data,
>  {
>  	struct eprobe_data *edata = data->private_data;
>  
> +	if (unlikely(!rec))
> +		return;
> +
>  	__eprobe_trace_func(edata, rec);
>  }
>  
> -- 
> 2.35.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>