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From: Kees Cook <keescook@chromium.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Christoph Hellwig <hch@lst.de>, Iurii Zaikin <yzaikin@google.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sysctl: Make sure proc handlers can't expose heap memory
Date: Tue, 5 May 2020 16:23:14 -0700	[thread overview]
Message-ID: <202005051621.90DE28B@keescook> (raw)
In-Reply-To: <20200505220327.GV11244@42.do-not-panic.com>

On Tue, May 05, 2020 at 10:03:27PM +0000, Luis Chamberlain wrote:
> On Tue, May 05, 2020 at 01:41:44PM -0700, Kees Cook wrote:
> > Right -- while it'd be nice if the developer noticed it, it is _usually_
> > an unsuspecting end user (or fuzzer), in which case we absolutely want a
> > WARN (and not a BUG![1]) and have the situations handled gracefully, so
> > it can be reported and fixed.
> 
> I've been using WARN*() for this exact purpose before, so I am as
> surprised as you are bout these concerns. However if we have folks

I don't see any mismatch here: it's not user-reachable, which is what
Greg said. WARN is for non-user-reachable "impossible situations". We
want to know if those can be hit (via bad API usage, races, etc). If
it's reachable from userspace, then it can't be a WARN() any more and
needs to be pr_warn().

> shipping with panic-on-warn this would be rather detrimental to our
> goals.
> 
> Greg, are you aware of folks shipping with panic-on-warn on some products?

People shipping with panic_on_warn are expecting to panic for WARNs like
this. :P

-- 
Kees Cook

  reply	other threads:[~2020-05-05 23:23 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-04 19:08 [PATCH] sysctl: Make sure proc handlers can't expose heap memory Kees Cook
2020-05-04 19:59 ` Luis Chamberlain
2020-05-04 20:32   ` Kees Cook
2020-05-04 21:59     ` Luis Chamberlain
2020-05-05  6:34       ` Greg KH
2020-05-05 20:41         ` Kees Cook
2020-05-05 22:03           ` Luis Chamberlain
2020-05-05 23:23             ` Kees Cook [this message]
2020-05-05  5:58 ` Christoph Hellwig

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