netdev - RE: [PATCH net] sctp: prevent info leak in sctp_make

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Date:   Tue, 29 Jun 2021 10:37:48 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andreas Fink' <afink@...t.fink.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
CC:     Vlad Yasevich <vyasevich@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        "Neil Horman" <nhorman@...driver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Jakub Kicinski" <kuba@...nel.org>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: RE: [PATCH net] sctp: prevent info leak in sctp_make_heartbeat()

> > -	struct sctp_sender_hb_info hbinfo;
> > +	struct sctp_sender_hb_info hbinfo = {};

> Does that gcc extension work with all compilers, especially clang?

> > So that's nice, because adding memset()s to zero everywhere was ugly.

The 'real fun' (tm) starts when the bit pattern for the NULL
pointer isn't 'all zeros'.
Using memset() is then broken - I suspect the compiler is
expected to initialise pointers to the correct NULL pattern.

Not that I think anyone sane would consider trying to compile
any 'normal' C code for such a system.

OTOH it is probably why clang is bleating about (int)((char *)0 + 4)
being undefined behaviour.

	David

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