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

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Message-ID: <2vxzv7gj7wv7.fsf@kernel.org>
Date: Fri, 30 Jan 2026 19:56:28 +0100
From: Pratyush Yadav <pratyush@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Pratyush Yadav <pratyush@...nel.org>,  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 Wed, Jan 28 2026, Mike Rapoport wrote:

> 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>

Thanks.

Andrew, do you mind taking this patch in v6.19-rc8/v6.19 hotfixes? The
second patch needs a re-roll and I don't think I would be able to do it
this week.

This is an independent fix and I see no reason to block this waiting for
the other one.

[...]

-- 
Regards,
Pratyush Yadav