<p>laforge <strong>submitted</strong> this change.</p><p><a href="https://gerrit.osmocom.org/c/libosmocore/+/21666">View Change</a></p><div style="white-space:pre-wrap">Approvals:
Jenkins Builder: Verified
laforge: Looks good to me, approved
</div><pre style="font-family: monospace,monospace; white-space: pre-wrap;">gprs_ns2_fr: guard against race between socket(AF_PACKET) and bind()<br><br>An AF_PACKET socket will immediately receive packets of _all_ interfaces<br>until it is bound to one specific interface. This introduces a race<br>condition between the socket() and the bind() syscall.<br><br>Let's use the ifindex passed for each packet in recvmsg() to drop<br>any packets received for other interfaces.<br><br>Change-Id: I8f708ba4f9b7f76525acce17b24a8f7b125a1c1c<br>Related: SYS#5245<br>---<br>M src/gb/gprs_ns2_fr.c<br>1 file changed, 23 insertions(+), 12 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/gb/gprs_ns2_fr.c b/src/gb/gprs_ns2_fr.c</span><br><span>index c774e11..0e4e2d3 100644</span><br><span>--- a/src/gb/gprs_ns2_fr.c</span><br><span>+++ b/src/gb/gprs_ns2_fr.c</span><br><span>@@ -86,6 +86,7 @@</span><br><span> struct osmo_fd fd;</span><br><span> char netif[IF_NAMESIZE];</span><br><span> struct osmo_fr_link *link;</span><br><span style="color: hsl(120, 100%, 40%);">+ int ifindex;</span><br><span> bool if_running;</span><br><span> };</span><br><span> </span><br><span>@@ -196,12 +197,14 @@</span><br><span> struct gprs_ns2_vc_bind *bind = bfd->data;</span><br><span> struct priv_bind *priv = bind->priv;</span><br><span> struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "Gb/NS/FR/GRE Rx");</span><br><span style="color: hsl(120, 100%, 40%);">+ struct sockaddr_ll sll;</span><br><span style="color: hsl(120, 100%, 40%);">+ socklen_t sll_len = sizeof(sll);</span><br><span> int rc = 0;</span><br><span> </span><br><span> if (!msg)</span><br><span> return -ENOMEM;</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- rc = read(bfd->fd, msg->data, NS_ALLOC_SIZE);</span><br><span style="color: hsl(120, 100%, 40%);">+ rc = recvfrom(bfd->fd, msg->data, NS_ALLOC_SIZE, 0, (struct sockaddr *)&sll, &sll_len);</span><br><span> if (rc < 0) {</span><br><span> LOGP(DLNS, LOGL_ERROR, "recv error %s during NS-FR-GRE recv\n",</span><br><span> strerror(errno));</span><br><span>@@ -210,6 +213,11 @@</span><br><span> goto out_err;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* ignore any packets that we might have received for a different interface, between</span><br><span style="color: hsl(120, 100%, 40%);">+ * the socket() and the bind() call */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (sll.sll_ifindex != priv->ifindex)</span><br><span style="color: hsl(120, 100%, 40%);">+ goto out_err;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> msgb_put(msg, rc);</span><br><span> msg->dst = priv->link;</span><br><span> return osmo_fr_rx(msg);</span><br><span>@@ -299,18 +307,11 @@</span><br><span> return ifr.ifr_ifindex;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">-static int open_socket(const char *ifname)</span><br><span style="color: hsl(120, 100%, 40%);">+static int open_socket(int ifindex)</span><br><span> {</span><br><span> struct sockaddr_ll addr;</span><br><span style="color: hsl(0, 100%, 40%);">- int ifindex;</span><br><span> int fd, rc;</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- ifindex = devname2ifindex(ifname);</span><br><span style="color: hsl(0, 100%, 40%);">- if (ifindex < 0) {</span><br><span style="color: hsl(0, 100%, 40%);">- LOGP(DLNS, LOGL_ERROR, "Can not get interface index for interface %s\n", ifname);</span><br><span style="color: hsl(0, 100%, 40%);">- return ifindex;</span><br><span style="color: hsl(0, 100%, 40%);">- }</span><br><span style="color: hsl(0, 100%, 40%);">-</span><br><span> memset(&addr, 0, sizeof(addr));</span><br><span> addr.sll_family = AF_PACKET;</span><br><span> addr.sll_protocol = htons(ETH_P_ALL);</span><br><span>@@ -318,13 +319,16 @@</span><br><span> </span><br><span> fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));</span><br><span> if (fd < 0) {</span><br><span style="color: hsl(0, 100%, 40%);">- LOGP(DLNS, LOGL_ERROR, "Can not get socket for interface %s. Are you root or have CAP_RAW_SOCKET?\n", ifname);</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGP(DLNS, LOGL_ERROR, "Can not create AF_PACKET socket. Are you root or have CAP_RAW_SOCKET?\n");</span><br><span> return fd;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* there's a race condition between the above syscall and the bind() call below,</span><br><span style="color: hsl(120, 100%, 40%);">+ * causing other packets to be received in between */</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> rc = bind(fd, (struct sockaddr *)&addr, sizeof(addr));</span><br><span> if (rc < 0) {</span><br><span style="color: hsl(0, 100%, 40%);">- LOGP(DLNS, LOGL_ERROR, "Can not bind for interface %s\n", ifname);</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGP(DLNS, LOGL_ERROR, "Can not bind AF_PACKET socket to ifindex %d\n", ifindex);</span><br><span> close(fd);</span><br><span> return rc;</span><br><span> }</span><br><span>@@ -496,7 +500,14 @@</span><br><span> fr_link->tx_cb = fr_tx_cb;</span><br><span> fr_link->tx_cb_data = bind;</span><br><span> priv->link = fr_link;</span><br><span style="color: hsl(0, 100%, 40%);">- priv->fd.fd = rc = open_socket(netif);</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ priv->ifindex = devname2ifindex(netif);</span><br><span style="color: hsl(120, 100%, 40%);">+ if (priv->ifindex < 0) {</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGP(DLNS, LOGL_ERROR, "Can not get interface index for interface %s\n", netif);</span><br><span style="color: hsl(120, 100%, 40%);">+ goto err_fr;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ priv->fd.fd = rc = open_socket(priv->ifindex);</span><br><span> if (rc < 0)</span><br><span> goto err_fr;</span><br><span> </span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/libosmocore/+/21666">change 21666</a>. 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<div style="display:none"> Gerrit-Project: libosmocore </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I8f708ba4f9b7f76525acce17b24a8f7b125a1c1c </div>
<div style="display:none"> Gerrit-Change-Number: 21666 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-Reviewer: Jenkins Builder </div>
<div style="display:none"> Gerrit-Reviewer: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-MessageType: merged </div>