linux-kernel - Re: [PATCH RESEND v4 1/1] test_firmware: fix some memory leaks and racing conditions

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Message-ID: <e9af482f-5b8a-70c0-d767-e98703cd1b03@alu.unizg.hr>
Date:   Thu, 27 Jul 2023 08:16:17 +0200
From:   Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Scott Branden <sbranden@...adcom.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russ Weight <russell.h.weight@...el.com>,
        linux-kernel@...r.kernel.org,
        Tianfei zhang <tianfei.zhang@...el.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Zhengchao Shao <shaozhengchao@...wei.com>,
        Colin Ian King <colin.i.king@...il.com>,
        Takashi Iwai <tiwai@...e.de>,
        Kees Cook <keescook@...omium.org>,
        Dan Carpenter <error27@...il.com>,
        Vincenzo Palazzo <vincenzopalazzodev@...il.com>
Subject: Re: [PATCH RESEND v4 1/1] test_firmware: fix some memory leaks and
 racing conditions

On 25.4.2023. 20:27, Luis Chamberlain wrote:
> On Fri, Apr 21, 2023 at 08:52:06PM +0200, Mirsad Goran Todorovac wrote:
>> Some functions were called both from locked and unlocked context, so
>> the lock was dropped prematurely, introducing a race condition when
>> deadlock was avoided.
>>
>> Having two locks wouldn't assure a race-proof mutual exclusion.
>>
>> __test_dev_config_update_bool(), __test_dev_config_update_u8() and
>> __test_dev_config_update_size_t() unlocked versions of the functions
>> were introduced to be called from the locked contexts as a workaround
>> without releasing the main driver's lock and causing a race condition.
>>
>> This should guarantee mutual exclusion and prevent any race conditions.
>>
>> Locked versions simply allow for mutual exclusion and call the unlocked
>> counterparts, to avoid duplication of code.
>>
>> trigger_batched_requests_store() and trigger_batched_requests_async_store()
>> now return -EBUSY if called with test_fw_config->reqs already allocated,
>> so the memory leak is prevented.
>>
>> The same functions now keep track of the allocated buf for firmware in
>> req->fw_buf as release_firmware() will not deallocate this storage for us.
>>
>> Additionally, in __test_release_all_firmware(), req->fw_buf is released
>> before calling release_firmware(req->fw),
>> foreach test_fw_config->reqs[i], i = 0 .. test_fw_config->num_requests-1
>>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: Luis Chamberlain <mcgrof@...nel.org>
>> Cc: Russ Weight <russell.h.weight@...el.com>
>> Cc: Tianfei zhang <tianfei.zhang@...el.com>
>> Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> Cc: Zhengchao Shao <shaozhengchao@...wei.com>
>> Cc: Colin Ian King <colin.i.king@...il.com>
>> Cc: linux-kernel@...r.kernel.org
>> Cc: Takashi Iwai <tiwai@...e.de>
>> Cc: Kees Cook <keescook@...omium.org>
>> Cc: Scott Branden <sbranden@...adcom.com>
>> Cc: Luis R. Rodriguez <mcgrof@...nel.org>
>> Suggested-by: Dan Carpenter <error27@...il.com>
>> Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
> 
> Mirad, thanks for this work, good stuff! So the patch just needs to be
> adjust with:
> 
> Fixes: 7feebfa487b92 ("test_firmware: add support for request_firmware_into_buf"
> Cc: stable@...r.kernel.org # v5.4
> 
> Then, can you split the patch in two, one which fixes the memory leaks
> and another that deals with the mutexes. The second patch might be a fix
> for the original code but I can't tell until I see the changes split out.
> 
> The commit log should account for the memory leak and be clear how it
> happens. The other commit log for the second patch should clarify what
> it fixes and why as well.

It seems to me that there is something wrong with the patchwork, as this commit
had not yet appeared in 5.4 LTS stable tree?

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/log/?qt=grep&q=Mirsad&h=linux-5.4.y

I was accidentally looking whether it passed, and it seems like more than a month
since the other commits propagated :-/

Thanks,
Mirsad

-- 
Mirsad Todorovac
System engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb
Republic of Croatia, the European Union

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