linux-hardening - Re: [RFC PATCH 0/2] Add cleanup_plugin for detecting problematic cleanup patterns

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Message-ID: <19a5480e34c.81108d211707508.5372983468552631527@linux.beauty>
Date: Wed, 05 Nov 2025 22:52:04 +0800
From: Li Chen <me@...ux.beauty>
To: "Peter Zijlstra" <peterz@...radead.org>
Cc: "Kees Cook" <kees@...nel.org>, "Nathan Chancellor" <nathan@...nel.org>,
	"Nicolas Schier" <nicolas.schier@...ux.dev>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"linux-hardening" <linux-hardening@...r.kernel.org>,
	"linux-kbuild" <linux-kbuild@...r.kernel.org>,
	"Dan Williams" <dan.j.williams@...el.com>,
	"Bjorn Helgaas" <bhelgaas@...gle.com>
Subject: Re: [RFC PATCH 0/2] Add cleanup_plugin for detecting problematic
 cleanup patterns

Hi Peter,

 ---- On Wed, 05 Nov 2025 17:49:04 +0800  Peter Zijlstra <peterz@...radead.org> wrote --- 
 > On Wed, Nov 05, 2025 at 05:04:02PM +0800, Li Chen wrote:
 > > +Peter, Dan, and Bjorn
 > > 
 > > (My apologies for the oversight)
 > > 
 > >  ---- On Wed, 05 Nov 2025 16:46:55 +0800  Li Chen <me@...ux.beauty> wrote --- 
 > >  > From: Li Chen <chenl311@...natelecom.cn>
 > >  > 
 > >  > Hello,
 > >  > 
 > >  > This patch series introduces a new GCC plugin called cleanup_plugin that
 > >  > warns developers about problematic patterns when using variables with
 > >  > __attribute__((cleanup(...))). The plugin addresses concerns documented
 > >  > in include/linux/cleanup.h regarding resource leaks and interdependency
 > >  > issues.
 > >  > 
 > >  > The cleanup attribute helpers (__free, DEFINE_FREE, etc.) are designed
 > >  > to automatically clean up resources when variables go out of scope,
 > >  > following LIFO (last in first out) ordering. However, certain patterns
 > >  > can lead to subtle bugs:
 > >  > 
 > >  > 1. Uninitialized cleanup variables: Variables declared with cleanup
 > >  >    attributes but not initialized can cause issues when cleanup functions
 > >  >    are called on undefined values.
 > >  > 
 > >  > 2. NULL-initialized cleanup variables: The "__free(...) = NULL" pattern
 > >  >    at function top can cause interdependency problems, especially when
 > >  >    combined with guards or multiple cleanup variables, as the cleanup
 > >  >    may run in unexpected contexts.
 > >  > 
 > >  > The plugin detects both of these problematic patterns and provides clear
 > >  > warnings to developers, helping prevent  incorrect cleanup ordering.
 > >  > Importantly, the plugin's warnings are not converted
 > >  > to errors by -Werror, allowing builds to continue while still alerting
 > >  > developers to potential issues.
 > >  > 
 > >  > The plugin is enabled by default as it provides valuable compile-time
 > >  > feedback without impacting build performance.
 > 
 > IIRC GCC also allow dumb stuff like gotos into the scope of a cleanup
 > variable, where clang will fail the compile. Does this plugin also fix
 > this?
 > 

I'm sorry, but I don't fully understand what you mean by "gotos into the 
scope of a cleanup variable". Could you please provide a sample to illustrate this issue?
And I would try to fix it here if I can.

Regards,

Li