From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Starke, Daniel" <daniel.starke@siemens.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v2] tty: n_gsm: restrict tty devices to attach
Date: Sun, 21 Apr 2024 22:28:19 +0900 [thread overview]
Message-ID: <6103a212-f84f-4dad-9d33-a18235bd970a@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <CAHk-=wjW3PdOZ7PJ+RHUKRc8SqQhcWXCACOvmwBkKUKABHKqwg@mail.gmail.com>
On 2024/04/21 3:05, Linus Torvalds wrote:
> On Sat, 20 Apr 2024 at 11:02, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> Most other normal tty devices just expect ->write() to be called in
>> normal process context, so if we do a line discipline flag, it would
> ^^^^^^^^^^^^^^^^^^^^
>> have to be something like "I'm ok with being called with interrupts
>> disabled", and then the n_gsm ->open function would just check that.
>
> Not line discipline - it would be a 'struct tty_operations' flag
> saying 'my ->write() function is ok with atomic context".
"struct tty_ldisc_ops" says that ->write() function (e.g. gsmld_write())
is allowed to sleep and "struct tty_operations" says that ->write() function
(e.g. con_write()) is not allowed to sleep. Thus, I initially proposed
https://lkml.kernel.org/r/9cd9d3eb-418f-44cc-afcf-7283d51252d6@I-love.SAKURA.ne.jp
which makes con_write() no-op when called with IRQs disabled.
My major/minor approach is based on a suggestion from Jiri that we just somehow
disallow attaching this line discipline to a console, with a concern from Starke
that introducing cross references is hard to maintain taken into account.
https://lkml.kernel.org/r/DB9PR10MB5881526A2B8F27FE36C49134E0CBA@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM
Now, your 'struct tty_operations' flag saying 'my ->write() function is OK with
atomic context' is expected to be set to all drivers.
Do we instead want to add 'struct tty_operations' flag saying 'my ->write() function
is NOT OK with atomic context' and turn on the flag for the console driver?
next prev parent reply other threads:[~2024-04-21 13:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-20 11:12 [PATCH v2] tty: n_gsm: restrict tty devices to attach Tetsuo Handa
2024-04-20 13:13 ` Greg Kroah-Hartman
2024-04-20 17:34 ` Linus Torvalds
2024-04-20 18:02 ` Linus Torvalds
2024-04-20 18:05 ` Linus Torvalds
2024-04-21 13:28 ` Tetsuo Handa [this message]
2024-04-21 16:04 ` Linus Torvalds
2024-04-21 17:18 ` Linus Torvalds
2024-04-23 15:26 ` Tetsuo Handa
2024-04-23 16:37 ` Linus Torvalds
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