Re: [PATCH] mhi: Fix double dma free

[Bhaumik Bhatt <bbhatt@codeaurora.org>]

Hi Loic, Mani, Hemant,

On 2021-02-09 10:17 AM, Loic Poulain wrote:
> Hi Bhaumik,
> 
> On Tue, 9 Feb 2021 at 18:27, Bhaumik Bhatt <bbhatt@codeaurora.org> 
> wrote:
>> 
>> On 2021-02-09 08:06 AM, Loic Poulain wrote:
>> > On Tue, 9 Feb 2021 at 16:55, Jeffrey Hugo <jhugo@codeaurora.org> wrote:
>> >>
>> >> On 2/9/2021 8:53 AM, Loic Poulain wrote:
>> >> > mhi_deinit_chan_ctxt functionthat takes care of unitializing channel
>> >> > resources, including unmapping coherent MHI areas, can be called
>> >> > from different path in case of controller unregistering/removal:
>> >> >   - From a client driver remove callback, via mhi_unprepare_channel
>> >> >   - From mhi_driver_remove that unitialize all channels
>> >> >
>> >> > mhi_driver_remove()
>> >> > |-> driver->remove()
>> >> > |    |-> mhi_unprepare_channel()
>> >> > |        |-> mhi_deinit_chan_ctxt()
>> >> > |...
>> >> > |-> mhi_deinit_chan_ctxt()
>> >> >
>> >> > This leads to double dma freeing...
>> >> >
>> >> > Fix that by preventing deinit for already uninitialized channel.
>> >> >
>> >> > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
>> >> > Reported-by: Kalle Valo <kvalo@codeaurora.org>
>> >> > ---
>> >>
>> >> Seems like this should have a Fixes: tag, no?
>> >
>> > Right, thanks, i'll add it in V2 once I get feedback.
>> 
>> Hi Loic, Mani,
>> 
>> I saw this same issue a while back but could not collect the logs for
>> it.
>> 
>> I had already pushed a patch to fix this differently [1] which was
>> recently reviewed by Hemant.
>> 
>> Although there wasn't a purposeful fixes tag for it. I think the 
>> culprit
>> for this issue is [2]:
>> 
>> As it allows the unprepare to go through on remove(), which was
>> traditionally not allowed and
>> ends up uncovering this issue as it fixes another.
>> 
>> Channel updates [3] address that and provide a bunch of other
>> improvements. Please consider them.
> 
> Yes, patch [2] is the culprit. I would recommend merging this tiny fix
> so that it can be easily grab for 5.11 or backported, and keep your
> series (rebased on top), for mhi-next (going to review/test it btw).
> 
> Regards,
> Loic

If priority is to get this fix in ASAP, your suggestion is OK. I just 
see some
typo fixes and a title update to "bus: mhi: core: Fix double dma free() 
call"
or something as review comments for your patch.

Another option is that I can send my patch [1] separately and remove it 
from my
"channel updates" patch series, if that helps.

I'd like to see what Mani and Hemant on what they prefer. Please advise.

Thanks,
Bhaumik

[1] https://lkml.org/lkml/2021/2/4/1161

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