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

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Message-ID: <YjtCY1QaA6GI3b+7@alley>
Date:   Wed, 23 Mar 2022 16:53:07 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     trix@...hat.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 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.

Best Regards,
Petr