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From:   Andreas Schwab <schwab@suse.de>
To:     Daniel Bristot de Oliveira <bristot@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rtla: fix double free
References: <mvmzggxl4n1.fsf@suse.de>
        <fd0888a4-099c-95fe-7e20-82be1489061f@kernel.org>
Date:   Mon, 25 Jul 2022 15:46:40 +0200
In-Reply-To: <fd0888a4-099c-95fe-7e20-82be1489061f@kernel.org> (Daniel Bristot
        de Oliveira's message of "Mon, 25 Jul 2022 15:34:56 +0200")
Message-ID: <mvmv8rll2yn.fsf@suse.de>
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On Jul 25 2022, Daniel Bristot de Oliveira wrote:

> Hi Andreas
>
> On 7/25/22 15:10, Andreas Schwab wrote:
>> Don't call trace_instance_destroy in trace_instance_init when it fails,
>> this is done by the caller.
>
> Regarding the Subject, are you seeing a double-free error, or it is just an
> optimization?

A double free nowadays is almost always an error, due to better malloc
checking.

> AFAICS, trace_instance_destroy() checks the pointers before calling free().

That doesn't help when the pointer is not cleared afterwards.  Do you
prefer that?

> Why am I asking? because if it is a double-free bug, we need to add the "Fixes:"
> tag,

It's the first time I tried running rtla, so I don't know whether it is
a regression, but from looking at the history it appears to have been
introduced already in commit 0605bf009f18 ("rtla: Add osnoise tool")

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."