linux-kernel - Re: [PATCH 1/2] liveupdate: luo_file: do not clear serialized

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Message-ID: <aXnwvkuTBL1NLt7f@kernel.org>
Date: Wed, 28 Jan 2026 13:19:26 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Pratyush Yadav <pratyush@...nel.org>
Cc: Pasha Tatashin <pasha.tatashin@...een.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] liveupdate: luo_file: do not clear serialized_data
 on unfreeze

On Tue, Jan 27, 2026 at 12:02:52AM +0100, Pratyush Yadav wrote:
> From: "Pratyush Yadav (Google)" <pratyush@...nel.org>
> 
> The unfreeze operation is supposed to undo the effects of the freeze
> operation. serialized_data is not set by freeze, but by preserve.
> Consequently, the unpreserve operation needs to access serialized_data
> to undo the effects of the preserve operation. This includes freeing
> the serialized data structures for example.
> 
> If a freeze callback fails, unfreeze is called for all frozen files.
> This would clear serialized_data for them. Since live update has failed,
> it can be expected that userspace aborts, releasing all sessions. When
> the sessions are released, unpreserve will be called for all files. The
> unfrozen files will see 0 in their serialized_data. This is not expected
> by file handlers, and they might either fail, leaking data and state, or
> might even crash or cause invalid memory access.
> 
> Do not clear serialized_data on unfreeze so it gets passed on to
> unpreserve. There is no need to clear it on unpreserve since luo_file
> will be freed immediately after.
> 
> Fixes: 7c722a7f44e0 ("liveupdate: luo_file: implement file systems callbacks")
> Signed-off-by: Pratyush Yadav (Google) <pratyush@...nel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

> ---
>  kernel/liveupdate/luo_file.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
> index a32a777f6df8..9f7283379ebc 100644
> --- a/kernel/liveupdate/luo_file.c
> +++ b/kernel/liveupdate/luo_file.c
> @@ -402,8 +402,6 @@ static void luo_file_unfreeze_one(struct luo_file_set *file_set,
>  
>  		luo_file->fh->ops->unfreeze(&args);
>  	}
> -
> -	luo_file->serialized_data = 0;
>  }
>  
>  static void __luo_file_unfreeze(struct luo_file_set *file_set,
> -- 
> 2.52.0.457.g6b5491de43-goog
> 

-- 
Sincerely yours,
Mike.