Re: Possible regression: unable to mount CIFS 1.0 shares from older machines since 76a3c92ec9e0668e4cd0e9ff1782eb68f61a179c

From: Thorsten Leemhuis <regressions@leemhuis.info>
To: Davyd McColl <davydm@gmail.com>,
	"lsahlber@redhat.com" <lsahlber@redhat.com>,
	"stfrench@microsoft.com" <stfrench@microsoft.com>
Cc: "linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"regressions@lists.linux.dev" <regressions@lists.linux.dev>
Subject: Re: Possible regression: unable to mount CIFS 1.0 shares from older machines since 76a3c92ec9e0668e4cd0e9ff1782eb68f61a179c
Date: Mon, 10 Jan 2022 13:15:02 +0100	[thread overview]
Message-ID: <ff982786-4033-7450-c10c-8ce71c28d6eb@leemhuis.info> (raw)
In-Reply-To: <D58238A4-F04E-458E-AB05-4A74235B2C65@getmailspring.com>

Hi, this is your Linux kernel regression tracker speaking.

On 10.01.22 06:53, Davyd McColl wrote:
> 
> I'm following advice from the thread at
> https://bugzilla.kernel.org/show_bug.cgi?id=215375
> <https://bugzilla.kernel.org/show_bug.cgi?id=215375> as to how to report
> this, so please bear with me and redirect me as necessary.
> 
> Since commit 76a3c92ec9e0668e4cd0e9ff1782eb68f61a179c,

FWIW, that is "cifs: remove support for NTLM and weaker authentication
algorithms"

> I'm unable to
> mount a CIFS 1.0 share ( from a media player: mede8er med600x3d, which
> runs some older linux). Apparently I'm not the only one, according to
> that thread, though the other affected party there is windows-based.
> 
> I first logged this in the Gentoo bugtracker
> (https://bugs.gentoo.org/821895 <https://bugs.gentoo.org/821895>) and a
> reversion patch is available there for the time being.
> 
> I understand that some of the encryption methods upon which the original
> feature relied are to be removed and, as such, the ability to mount
> these older shares was removed. This is sure to affect anyone running
> older Windows virtual machines (or older, internally-visible windows
> hosts) in addition to anyone attempting to connect to shares from
> esoteric devices like mine.

> Whilst I understand the desire to clean up code and remove dead
> branches, I'd really appreciate it if this particular feature remains
> available either by kernel configuration (which suits me fine, but is
> likely to be a hassle for anyone running a binary distribution) or via
> boot parameters. In the mean-time, I'm updating my own sync software to
> support this older device because if I can't sync media to the player,
> the device is not very useful to me.

From my point of view this afaics looks like one of those issues where
the "no regressions" rule gets tricky. But I told Davyd to bring it
forward here to get it discussed in the open. I also wonder if some
middle-ground solution could be found in this particular case -- e.g.
one where the commit stated above gets reverted and the code then
slightly changed to only allow weaker authentication if the user
manually requests in somehow, for example using a module parameter or
something in /proc or /sys.

Ciao, Thorsten

P.S.: Anyway, getting this tracked:

#regzbot ^introduced 76a3c92ec9e0668e4cd0e9ff1782eb68f61a179c
#regzbot title cifs: unable to shares that require NTLM or weaker
authentication algorithms
#regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=215375