From: Kees Cook <keescook@chromium.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
Alex Elder <elder@linaro.org>,
corbet@lwn.net, workflows@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Documentation: coding-style: don't encourage WARN*()
Date: Mon, 15 Apr 2024 09:26:40 -0700 [thread overview]
Message-ID: <202404150919.042E6FF@keescook> (raw)
In-Reply-To: <2024041544-fester-undead-7949@gregkh>
On Mon, Apr 15, 2024 at 10:35:21AM +0200, Greg KH wrote:
> On Mon, Apr 15, 2024 at 01:07:41AM -0700, Christoph Hellwig wrote:
> > No, this advice is wronger than wrong. If you set panic_on_warn you
> > get to keep the pieces.
> >
>
> But don't add new WARN() calls please, just properly clean up and handle
> the error. And any WARN() that userspace can trigger ends up triggering
> syzbot reports which also is a major pain, even if you don't have
> panic_on_warn enabled.
Here's what was more recently written on WARN:
https://docs.kernel.org/process/deprecated.html#bug-and-bug-on
Specifically:
- never use BUG*()
- WARN*() should only be used for "expected to be unreachable" situations
This, then, maps correctly to panic_on_warn: System owners may have set
the panic_on_warn sysctl, to make sure their systems do not continue
running in the face of "unreachable" conditions.
As in, userspace should _never_ be able to reach a WARN(). If it can,
either the logic leading to it needs to be fixed, or the WARN() needs to
be changed to a pr_warn().
--
Kees Cook
next prev parent reply other threads:[~2024-04-15 16:26 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-14 17:08 [PATCH] Documentation: coding-style: don't encourage WARN*() Alex Elder
2024-04-14 19:48 ` Laurent Pinchart
2024-04-14 20:06 ` Alex Elder
2024-04-15 5:21 ` Greg KH
2024-04-15 8:25 ` Laurent Pinchart
2024-04-15 8:33 ` Greg KH
2024-04-15 8:42 ` Laurent Pinchart
2024-04-15 5:22 ` Greg KH
2024-04-15 8:07 ` Christoph Hellwig
2024-04-15 8:35 ` Greg KH
2024-04-15 8:46 ` Christoph Hellwig
2024-04-15 16:26 ` Kees Cook [this message]
2024-04-18 15:57 ` Jason Gunthorpe
2024-04-18 16:14 ` Eric Biggers
2024-04-18 17:12 ` Kees Cook
2024-04-18 22:33 ` John Hubbard
2024-04-19 7:16 ` David Hildenbrand
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