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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id y29sm1546916qkj.8.2019.06.21.07.56.04 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 21 Jun 2019 07:56:04 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1heKxQ-00014G-1d; Fri, 21 Jun 2019 11:56:04 -0300 Date: Fri, 21 Jun 2019 11:56:04 -0300 From: Jason Gunthorpe To: Dag Moxnes Cc: dledford@redhat.com, leon@kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Parav Pandit Subject: Re: [PATCH] RDMA/core: Fix race when resolving IP address Message-ID: <20190621145604.GS19891@ziepe.ca> References: <1561126156-10162-1-git-send-email-dag.moxnes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1561126156-10162-1-git-send-email-dag.moxnes@oracle.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 21, 2019 at 04:09:16PM +0200, Dag Moxnes wrote: > Use neighbour lock when copying MAC address from neighbour data struct > in dst_fetch_ha. > > When not using the lock, it is possible for the function to race with > neigh_update, causing it to copy an invalid MAC address. > > It is possible to provoke this error by calling rdma_resolve_addr in a > tight loop, while deleting the corresponding ARP entry in another tight > loop. > > Signed-off-by: Dag Moxnes > Change-Id: I3c5f982b304457f0a83ea7def2fac70315ed38b4 > drivers/infiniband/core/addr.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c > index 2f7d141598..e4945fd1bb 100644 > +++ b/drivers/infiniband/core/addr.c > @@ -333,12 +333,16 @@ static int dst_fetch_ha(const struct dst_entry *dst, > if (!n) > return -ENODATA; > > + read_lock_bh(&n->lock) > if (!(n->nud_state & NUD_VALID)) { > - neigh_event_send(n, NULL); > ret = -ENODATA; > } else { > memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN); > } > + read_unlock_bh(&n->lock); > + > + if (ret) > + neigh_event_send(n, NULL); > > neigh_release(n); Can we write this with less spaghetti please, maybe: static int dst_fetch_ha(const struct dst_entry *dst, struct rdma_dev_addr *dev_addr, const void *daddr) { struct neighbour *n; int ret = 0; n = dst_neigh_lookup(dst, daddr); if (!n) return -ENODATA; read_lock_bh(&n->lock); if (!(n->nud_state & NUD_VALID)) { read_unlock_bh(&n->lock); goto out_send; } memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN); read_unlock_bh(&n->lock); goto out_release; out_send: neigh_event_send(n, NULL); ret = -ENODATA; out_release: neigh_release(n); return ret; } Also, Parav should look at it. Thanks, Jason