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Date:      Tue, 7 Dec 2021 15:13:17 -0800
From:      Gleb Smirnoff <glebius@freebsd.org>
To:        Hans Petter Selasky <hps@selasky.org>
Cc:        src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org
Subject:   Re: git: e3044071dec1 - main - in6p_set_multicast_if(): fix malloc(M_WAITOK) with epoch
Message-ID:  <Ya/qjaaabw8sXxMB@FreeBSD.org>
In-Reply-To: <bba8c856-7105-a644-5c73-db7bfd232b60@selasky.org>
References:  <202112062236.1B6Ma4e0073785@gitrepo.freebsd.org> <bba8c856-7105-a644-5c73-db7bfd232b60@selasky.org>

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On Tue, Dec 07, 2021 at 08:36:58AM +0100, Hans Petter Selasky wrote:
H> > --- a/sys/netinet6/in6_mcast.c
H> > +++ b/sys/netinet6/in6_mcast.c
H> > @@ -2454,9 +2454,9 @@ in6p_set_multicast_if(struct inpcb *inp, struct sockopt *sopt)
H> >   			return (EADDRNOTAVAIL);
H> >   		}
H> >   	}
H> > +	NET_EPOCH_EXIT(et);	/* XXXGL: unsafe ifp */
H> >   	imo = in6p_findmoptions(inp);
H> > -	imo->im6o_multicast_ifp = ifp;	/* XXXGL: reference?! */
H> > -	NET_EPOCH_EXIT(et);
H> > +	imo->im6o_multicast_ifp = ifp;
H> >   	INP_WUNLOCK(inp);
H> >   
H> >   	return (0);
H> > 
H> 
H> You can ref the ifp before the EPOCH exit?

Sure. The code should use ifnet_byindex_ref().

Note that d74b7baeb0d4 was a sweep commit to "cover" all
unsafe uses of ifnet_byindex().  It was not my intent to
fix all of them, but rather mark them with a comment
and put NET_EPOCH_ASSERT() inside ifnet_byindex() to prevent
future unsafe calls.

-- 
Gleb Smirnoff



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