linux-kernel - Re: d7be102f29 ("cfg80211: initialize regulatory keys/database later"): kernel BUG at crypto/asymmetric_keys/public

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Message-ID: <23794.1511825150@warthog.procyon.org.uk>
Date:   Mon, 27 Nov 2017 23:25:50 +0000
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com, Fengguang Wu <fengguang.wu@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Josh Boyer <jwboyer@...hat.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Xiaolong Ye <xiaolong.ye@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>
Subject: Re: d7be102f29 ("cfg80211: initialize regulatory keys/database later"): kernel BUG at crypto/asymmetric_keys/public_key.c:80!

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> I'm not seeing why it would ever be ok to do BUG_ON() instead of just
> returning an error, though.

This function has a list of requisite parameters for the caller:

	BUG_ON(!pkey);		<-- You need the public key to use,
	BUG_ON(!sig);
	BUG_ON(!sig->digest);	<-- the message digest to check
	BUG_ON(!sig->s);	<-- and you need the signature.

If you fail to obtain any one of these parameters, you can't use this function
and you should have errored out before calling this function.  It seems
reasonable for the function to assume that you've provided them - they're kind
of essential to the operation.  If you want, I can just remove the checks
entirely.  Many of the kernel's functions don't perform argument checking, but
just assume you've done it right and will oops if you haven't.

I could just return -EINVAL, yes, but I'm not sure that's really the right
thing to do, at least not without printing an error message, since it's a
kernel programming error not a userspace error or data error.

David