linux-kernel - Re: [PATCH v5] printk: Userspace format enumeration support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YHmXi303WxVZzVwI@chrisdown.name>
Date:   Fri, 16 Apr 2021 14:56:27 +0100
From:   Chris Down <chris@...isdown.name>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>, kernel-team@...com
Subject: Re: [PATCH v5] printk: Userspace format enumeration support

Hey Petr, Rasmus,

Apologies for the delay, I've been out ill for a while so I'm just coming back 
to look at this.

Petr Mladek writes:
>> Anyway, on to the other thing I mentioned on dev_err and friends: I
>> think it would improve readability and make it a lot easier to (probably
>> in a later patch) add support for all those dev_* and net_* and whatever
>> other subsystems have their own wrappers
>
>This is great point! There are many other subsystem specific wrappers,
>e,g, ata_dev_printk(), netdev_printk(), snd_printk(), dprintk().
>We should make it easy to index them as well.

These would be nice to have, but we should agree about how we store things 
internally.

For example, in printk we typically store the level inline as part of the 
format string at compile time. However, for `dev_printk`, it's passed entirely 
separately from the format string after preprocessing is already concluded (or 
at least, not in a way we can easily parse it the same way we do for 
printk()):

	void dev_printk(const char *level, const struct device *dev, const char *fmt, ...)

One (ugly) way to handle this would be to have a new "level" field in the 
printk index entry, with semantics that if it's some sentinel value, look at 
the format itself for the format, otherwise if it's some other value, the level 
field itself is the level.

This will work, but it's pretty ugly. Any better suggestions? :-)

Thanks,

Chris