linux-ext4 - Re: [PATCH v5.15.y] Revert "fanotify: Allow users to request FAN_FS

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Message-ID: <CAOQ4uxjDM00vuQfw4m3+eph4iSxqrvFu7-WNfuZ4BApv58gQ-g@mail.gmail.com>
Date: Wed, 24 Jul 2024 09:42:57 +0300
From: Amir Goldstein <amir73il@...il.com>
To: Gabriel Krisman Bertazi <gabriel@...sman.be>
Cc: cel@...nel.org, gregkh@...uxfoundation.org, jack@...e.cz, 
	sashal@...nel.org, stable@...r.kernel.org, adilger.kernel@...ger.ca, 
	linux-ext4@...r.kernel.org, tytso@....edu, alexey.makhalov@...adcom.com, 
	vasavi.sirnapalli@...adcom.com, florian.fainelli@...adcom.com, 
	Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v5.15.y] Revert "fanotify: Allow users to request
 FAN_FS_ERROR events"

On Wed, Jul 24, 2024 at 2:24 AM Gabriel Krisman Bertazi
<gabriel@...sman.be> wrote:
>
> cel@...nel.org writes:
>
> > From: Chuck Lever <chuck.lever@...cle.com>
> >
> > Gabriel says:
> >> 9709bd548f11 just enabled a new feature -
> >> which seems against stable rules.  Considering that "anything is
> >> a CVE", we really need to be cautious about this kind of stuff in
> >> stable kernels.
> >>
> >> Is it possible to drop 9709bd548f11 from stable instead?
> >
> > The revert wasn't clean, but adjusting it to fit was straightforward.
> > This passes NFSD CI, and adds no new failures to the fanotify ltp
> > tests.
> >
> > Reported-by: Gabriel Krisman Bertazi <gabriel@...sman.be>
> > Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
> > ---
> >  fs/notify/fanotify/fanotify_user.c | 4 ----
> >  include/linux/fanotify.h           | 6 +-----
> >  2 files changed, 1 insertion(+), 9 deletions(-)
> >
> > Gabriel, is this what you were thinking?
>
> Thanks Chuck.
>
> This looks good to me as a way to disable it in stable and prevent
> userspace from trying to use it. Up to fanotify maintainers to decide
> whether to bring the rest of the series or merge this,

First of all, the "rest of the series" is already queued for 5.10.y.

I too was a bit surprised from willingness of stable tree maintainers
to allow backports of entire features along with Chuck's nfsd backports.
I understand the logic, I was just not aware when this shift in stable ideology
had happened.

But having backported the entire fanotify 6.1 code as is to 5.15 and 5.10
I see no reason to make an exception for FAN_FS_ERROR.
Certainly not because two patches were left out of 5.10.y (and are now queued).

I think that the benefits of fanotify code parity across 6.1 5.15 5.10
outweigh the risk of regressions introduced by this specific feature.

So please do not revert.

Thanks,
Amir.