Date: Tue, 18 Feb 2020 12:37:49 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Gleb Smirnoff <glebius@freebsd.org>, bz@freebsd.org Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r358013 - in head/sys: net netinet netinet6 Message-ID: <6bbdea0e-c42e-6296-2a13-3dbae1d1cdc7@selasky.org> In-Reply-To: <20200218004423.GG5741@FreeBSD.org> References: <202002170946.01H9kWAh078738@repo.freebsd.org> <20200218004423.GG5741@FreeBSD.org>
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On 2020-02-18 01:44, Gleb Smirnoff wrote: > On Mon, Feb 17, 2020 at 09:46:32AM +0000, Hans Petter Selasky wrote: > H> Author: hselasky > H> Date: Mon Feb 17 09:46:32 2020 > H> New Revision: 358013 > H> URL: https://svnweb.freebsd.org/changeset/base/358013 > H> > H> Log: > H> Fix kernel panic while trying to read multicast stream. > H> > H> When VIMAGE is enabled make sure the "m_pkthdr.rcvif" pointer is set > H> for all mbufs being input by the IGMP/MLD6 code. Else there will be a > H> NULL-pointer dereference in the netisr code when trying to set the > H> VNET based on the incoming mbuf. Add an assert to catch this when > H> queueing mbufs on a netisr to make debugging of similar cases easier. > H> > H> Found by: Vladislav V. Prodan > H> PR: 244002 > H> Reviewed by: bz@ > H> MFC after: 1 week > H> Sponsored by: Mellanox Technologies > H> > H> Modified: > H> head/sys/net/netisr.c > H> head/sys/netinet/igmp.c > H> head/sys/netinet6/mld6.c > H> > H> Modified: head/sys/net/netisr.c > H> ============================================================================== > H> --- head/sys/net/netisr.c Mon Feb 17 01:59:55 2020 (r358012) > H> +++ head/sys/net/netisr.c Mon Feb 17 09:46:32 2020 (r358013) > H> @@ -1056,6 +1056,8 @@ netisr_queue_src(u_int proto, uintptr_t source, struct > H> if (m != NULL) { > H> KASSERT(!CPU_ABSENT(cpuid), ("%s: CPU %u absent", __func__, > H> cpuid)); > H> + VNET_ASSERT(m->m_pkthdr.rcvif != NULL, > H> + ("%s:%d rcvif == NULL: m=%p", __func__, __LINE__, m)); > H> error = netisr_queue_internal(proto, m, cpuid); > H> } else > H> error = ENOBUFS; > H> > H> Modified: head/sys/netinet/igmp.c > H> ============================================================================== > H> --- head/sys/netinet/igmp.c Mon Feb 17 01:59:55 2020 (r358012) > H> +++ head/sys/netinet/igmp.c Mon Feb 17 09:46:32 2020 (r358013) > H> @@ -303,6 +303,7 @@ igmp_save_context(struct mbuf *m, struct ifnet *ifp) > H> #ifdef VIMAGE > H> m->m_pkthdr.PH_loc.ptr = ifp->if_vnet; > H> #endif /* VIMAGE */ > H> + m->m_pkthdr.rcvif = ifp; > H> m->m_pkthdr.flowid = ifp->if_index; > H> } > H> > H> > H> Modified: head/sys/netinet6/mld6.c > H> ============================================================================== > H> --- head/sys/netinet6/mld6.c Mon Feb 17 01:59:55 2020 (r358012) > H> +++ head/sys/netinet6/mld6.c Mon Feb 17 09:46:32 2020 (r358013) > H> @@ -283,6 +283,7 @@ mld_save_context(struct mbuf *m, struct ifnet *ifp) > H> #ifdef VIMAGE > H> m->m_pkthdr.PH_loc.ptr = ifp->if_vnet; > H> #endif /* VIMAGE */ > H> + m->m_pkthdr.rcvif = ifp; > H> m->m_pkthdr.flowid = ifp->if_index; > H> } > > This functions igmp_save_context() and mld_save_context() were clearly > designed to avoid dereferencing an ifnet pointer after a packet has been > queued and dequeued on IGMP/MLD internal queue. > > This patch now replicates the exactly same problem but with netisr > queue. Of course netisr not always queues, sometimes dispatches > directly, but it may do queue. > > I think same thing needs to be done to netisr internally - don't > dereference m->m_pkthdr.rcvif on dequeued packets, but store the > vnet info in the m->m_pkthdr.PH_loc.ptr before queueing. > Hi, I agree the if_vnet could be de-referenced in general when queueing a packet for the netisr. Are we certain that m->m_pkthdr.PH_loc.ptr is always available? Should then the netisr clear the rcvif? Or is this too dangerous? Then further, overriding the VNET inside the IGMP/MLD6 packet handler should be removed, because this is done inside the netisr. --HPS
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