linux-kernel - Re: [PATCH] cgroup: debug: Fix multiple issues in debug controller implementation

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Message-ID: <aLzeVZmxuNH1sxCq@bombadil.infradead.org>
Date: Sat, 6 Sep 2025 18:22:29 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: Fidal Palamparambil <rootuserhere@...il.com>
Cc: linux-modules@...r.kernel.org, petr.pavlu@...e.com, da.gomez@...nel.org,
	samitolvanen@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cgroup: debug: Fix multiple issues in debug controller
 implementation

On Sat, Sep 06, 2025 at 04:44:17PM +0400, Fidal Palamparambil wrote:
> From: Fidal palamparambil <rootuserhere@...il.com>
> 
> This commit addresses several issues in the cgroup debug controller:
> 
> 1. Memory leak protection in current_css_set_cg_links_read():
>    - Initialize name_buf to NULL and use proper error handling with goto
>    - Ensure memory is freed in all code paths
> 
> 2. RCU locking correctness:
>    - Use lockdep_is_held() for proper lock dependency tracking in
>      rcu_dereference_protected() calls
>    - Ensure proper locking context is passed to RCU checks
> 
> 3. Buffer size safety:
>    - Remove off-by-one in snprintf() size calculation
>    - Use sizeof(buffer) instead of sizeof(buffer)-1
> 
> 4. Code robustness:
>    - Add proper initialization of variables
>    - Use consistent error handling patterns
>    - Fix potential integer underflow in extra reference calculation
> 
> The debug controller is for internal debugging only, but these fixes
> ensure it doesn't introduce stability issues or memory leaks when
> used for debugging purposes.
> 
> Signed-off-by: Fidal palamparambil <rootuserhere@...il.com>

We really need to just ban you.

 Luis