linux-kernel - Re: [PATCH AUTOSEL 4.20 34/81] debugfs: return error values, not NULL

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Date:   Mon, 11 Mar 2019 13:22:28 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.20 34/81] debugfs: return error values, not NULL

On Thu, Feb 28, 2019 at 04:25:01PM +0100, Greg Kroah-Hartman wrote:
>On Thu, Feb 28, 2019 at 10:07:26AM -0500, Sasha Levin wrote:
>> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>
>> [ Upstream commit ff9fb72bc07705c00795ca48631f7fffe24d2c6b ]
>>
>> When an error happens, debugfs should return an error pointer value, not
>> NULL.  This will prevent the totally theoretical error where a debugfs
>> call fails due to lack of memory, returning NULL, and that dentry value
>> is then passed to another debugfs call, which would end up succeeding,
>> creating a file at the root of the debugfs tree, but would then be
>> impossible to remove (because you can not remove the directory NULL).
>>
>> So, to make everyone happy, always return errors, this makes the users
>> of debugfs much simpler (they do not have to ever check the return
>> value), and everyone can rest easy.
>>
>> Reported-by: Gary R Hook <ghook@....com>
>> Reported-by: Heiko Carstens <heiko.carstens@...ibm.com>
>> Reported-by: Masami Hiramatsu <mhiramat@...nel.org>
>> Reported-by: Michal Hocko <mhocko@...nel.org>
>> Reported-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>> Reported-by: Ulf Hansson <ulf.hansson@...aro.org>
>> Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
>> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  fs/debugfs/inode.c | 39 ++++++++++++++++++++++-----------------
>>  1 file changed, 22 insertions(+), 17 deletions(-)
>
>As much as I would love to backport this patch, no, please do not, I did
>not mark it for stable on purpose.  It can cause regressions with code
>that is not expecting this behavior (I have a fix that needs to go into
>5.0 for this very reason.)
>
>Please drop it from all queues.

I've dropped this and the rest of the debugfs related patches you've
pointed out, thank you.

--
Thanks,
Sasha