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

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Date:   Thu, 27 Jul 2023 15:45:26 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
Cc:     Scott Branden <sbranden@...adcom.com>,
        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 Fri, Jul 28, 2023 at 12:14:22AM +0200, Mirsad Todorovac wrote:
> On 7/27/23 17:36, Luis Chamberlain wrote:
> > On Thu, Jul 27, 2023 at 08:16:17AM +0200, Mirsad Todorovac wrote:
> > > 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?
> > 
> > Did you resend a new v5 with the requested changes?
> 
> Actually, I am not sure what is the procedure, for it is accepted and visible in 5.10+ trees?

Ah its upstream but not on v5.4. Just send a patch to stable folks and
include its commit IDs as stable patches typically do.

  Luis