linux-kernel - Re: [PATCH] perf probe: Fix null pointer dereference in convert_variable

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Message-ID: <YLY06O/Dk/2jpCB7@kernel.org>
Date:   Tue, 1 Jun 2021 10:23:52 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Li Huafei <lihuafei1@...wei.com>
Cc:     mhiramat@...nel.org, namhyung@...nel.org, peterz@...radead.org,
        mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        srikar@...ux.vnet.ibm.com, fche@...hat.com, Jianlin.Lv@....com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        yangjihong1@...wei.com, zhangjinhao2@...wei.com
Subject: Re: [PATCH] perf probe: Fix null pointer dereference in
 convert_variable_location()

Em Tue, Jun 01, 2021 at 05:27:50PM +0800, Li Huafei escreveu:
> If we just check whether the variable can be converted, 'tvar' should be
> a null pointer. However, the null pointer check is missing in the
> 'Constant value' execution path.
> 
> The following cases can trigger this problem:
> 
> 	$ cat test.c
> 	#include <stdio.h>

Thanks for providing the detailed analysis and test steps, I've
reproduced the problem before the patch and it now works with your
patch:

[acme@...e tmp]$ sudo perf probe -x ./test main:6
Added new event:
  probe_test:main_L6   (on main:6 in /tmp/test)

You can now use it in all perf tools, such as:

	perf record -e probe_test:main_L6 -aR sleep 1

[acme@...e tmp]$

Thanks, applied.

- Arnaldo