linux-kernel - Re: [PATCH v2] livepatch: Reorder to use before freeing a pointer

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Message-ID: <be3ac729-8d1d-0c2e-6d63-aeb23ca04bbd@redhat.com>
Date:   Wed, 23 Mar 2022 09:17:35 -0700
From:   Tom Rix <trix@...hat.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     jpoimboe@...hat.com, jikos@...nel.org, mbenes@...e.cz,
        joe.lawrence@...hat.com, nathan@...nel.org,
        ndesaulniers@...gle.com, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v2] livepatch: Reorder to use before freeing a pointer


On 3/23/22 8:53 AM, Petr Mladek wrote:
> On Sat 2022-03-19 18:51:43, trix@...hat.com wrote:
>> From: Tom Rix <trix@...hat.com>
>>
>> Clang static analysis reports this issue
>> livepatch-shadow-fix1.c:113:2: warning: Use of
>>    memory after it is freed
>>    pr_info("%s: dummy @ %p, prevented leak @ %p\n",
>>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> The pointer is freed in the previous statement.
>> Reorder the pr_info to report before the free.
>>
>> Similar issue in livepatch-shadow-fix2.c
> I have added the following paragraph:
>
> <snip>
> Note that it is a false positive. pr_info() just prints the address.
> The freed memory is not accessed. Well, the static analyzer could not
> know this easily.
> </snip>
>
>> Signed-off-by: Tom Rix <trix@...hat.com>
> and pushed the patch into livepatching/livepatching.git,
> branch for-5.18/selftests-fixes.
>
> IMHO, the patch is so trivial and can be added even in this merge
> window. There is no need to create more dances around it ;-)
>
> Let me know if you disagree. I am going to send the pull request
> on Friday or Monday.

Do whatever is easier for you.  The addition to the commit log is fine.

Thanks

Tom

>
> Best Regards,
> Petr
>