<p>Vadim Yanitskiy has uploaded this change for <strong>review</strong>.</p><p><a href="https://gerrit.osmocom.org/10137">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">trxcon/scheduler: fix: check primitive len before encoding<br><br>We used to trust (and still doing this) the messages coming from<br>L1CTL interface too much, and not to check the primitive length<br>before passing the payload to the libosmocoding API. As was<br>discovered and described in OS#3415, sending a L1CTL message<br>(either DATA_REQ, or TRAFFIC_REQ) with an incorrect length<br>(lower than expected) may cause heap overflow.<br><br>Let's explicitly check a primitive before encoding, and drop it<br>if its length doesn't match the expected value(s).<br><br>Change-Id: I258ee9f6d0124b183b1db23a73f1e523fcea89a8<br>Fixes: OS#3415<br>---<br>M src/host/trxcon/sched_lchan_rach.c<br>M src/host/trxcon/sched_lchan_tchf.c<br>M src/host/trxcon/sched_lchan_xcch.c<br>3 files changed, 29 insertions(+), 3 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/37/10137/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/host/trxcon/sched_lchan_rach.c b/src/host/trxcon/sched_lchan_rach.c</span><br><span>index 3f6e2e1..a255efb 100644</span><br><span>--- a/src/host/trxcon/sched_lchan_rach.c</span><br><span>+++ b/src/host/trxcon/sched_lchan_rach.c</span><br><span>@@ -69,6 +69,15 @@</span><br><span>    uint8_t payload[36];</span><br><span>         int rc;</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+   /* Check the prim payload length */</span><br><span style="color: hsl(120, 100%, 40%);">+   if (lchan->prim->payload_len != sizeof(*req)) {</span><br><span style="color: hsl(120, 100%, 40%);">+         LOGP(DSCHD, LOGL_ERROR, "Primitive has odd length %zu (expected %zu), "</span><br><span style="color: hsl(120, 100%, 40%);">+                     "so dropping...\n", lchan->prim->payload_len, sizeof(*req));</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+                sched_prim_drop(lchan);</span><br><span style="color: hsl(120, 100%, 40%);">+               return -EINVAL;</span><br><span style="color: hsl(120, 100%, 40%);">+       }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span>  /* Get the payload from a current primitive */</span><br><span>       req = (struct l1ctl_rach_req *) lchan->prim->payload;</span><br><span> </span><br><span>diff --git a/src/host/trxcon/sched_lchan_tchf.c b/src/host/trxcon/sched_lchan_tchf.c</span><br><span>index 80e4d52..e20b461 100644</span><br><span>--- a/src/host/trxcon/sched_lchan_tchf.c</span><br><span>+++ b/src/host/trxcon/sched_lchan_tchf.c</span><br><span>@@ -232,9 +232,17 @@</span><br><span>          return -EINVAL;</span><br><span>      }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">-   /* Determine payload length */</span><br><span style="color: hsl(0, 100%, 40%);">-  if (lchan->prim->payload_len == GSM_MACBLOCK_LEN)</span><br><span style="color: hsl(0, 100%, 40%);">-         l2_len = GSM_MACBLOCK_LEN;</span><br><span style="color: hsl(120, 100%, 40%);">+    /* Determine and check the payload length */</span><br><span style="color: hsl(120, 100%, 40%);">+  if (lchan->prim->payload_len == GSM_MACBLOCK_LEN) {</span><br><span style="color: hsl(120, 100%, 40%);">+             l2_len = GSM_MACBLOCK_LEN; /* FACCH */</span><br><span style="color: hsl(120, 100%, 40%);">+        } else if (lchan->prim->payload_len != l2_len) {</span><br><span style="color: hsl(120, 100%, 40%);">+                LOGP(DSCHD, LOGL_ERROR, "Primitive has odd length %zu "</span><br><span style="color: hsl(120, 100%, 40%);">+                     "(expected %zu for TCH or %u for FACCH), so dropping...\n",</span><br><span style="color: hsl(120, 100%, 40%);">+                 lchan->prim->payload_len, l2_len, GSM_MACBLOCK_LEN);</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+          sched_prim_drop(lchan);</span><br><span style="color: hsl(120, 100%, 40%);">+               return -EINVAL;</span><br><span style="color: hsl(120, 100%, 40%);">+       }</span><br><span> </span><br><span>        /* Shift buffer by 4 bursts back for interleaving */</span><br><span>         memcpy(buffer, buffer + 464, 464);</span><br><span>diff --git a/src/host/trxcon/sched_lchan_xcch.c b/src/host/trxcon/sched_lchan_xcch.c</span><br><span>index 04c9f4e..b31f727 100644</span><br><span>--- a/src/host/trxcon/sched_lchan_xcch.c</span><br><span>+++ b/src/host/trxcon/sched_lchan_xcch.c</span><br><span>@@ -141,6 +141,15 @@</span><br><span>                       return 0;</span><br><span>    }</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* Check the prim payload length */</span><br><span style="color: hsl(120, 100%, 40%);">+   if (lchan->prim->payload_len != GSM_MACBLOCK_LEN) {</span><br><span style="color: hsl(120, 100%, 40%);">+             LOGP(DSCHD, LOGL_ERROR, "Primitive has odd length %zu (expected %u), "</span><br><span style="color: hsl(120, 100%, 40%);">+                      "so dropping...\n", lchan->prim->payload_len, GSM_MACBLOCK_LEN);</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+            sched_prim_drop(lchan);</span><br><span style="color: hsl(120, 100%, 40%);">+               return -EINVAL;</span><br><span style="color: hsl(120, 100%, 40%);">+       }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span>  /* Encode payload */</span><br><span>         rc = gsm0503_xcch_encode(buffer, lchan->prim->payload);</span><br><span>        if (rc) {</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/10137">change 10137</a>. To unsubscribe, or for help writing mail filters, visit <a href="https://gerrit.osmocom.org/settings">settings</a>.</p><div itemscope itemtype="http://schema.org/EmailMessage"><div itemscope itemprop="action" itemtype="http://schema.org/ViewAction"><link itemprop="url" href="https://gerrit.osmocom.org/10137"/><meta itemprop="name" content="View Change"/></div></div>

<div style="display:none"> Gerrit-Project: osmocom-bb </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-MessageType: newchange </div>
<div style="display:none"> Gerrit-Change-Id: I258ee9f6d0124b183b1db23a73f1e523fcea89a8 </div>
<div style="display:none"> Gerrit-Change-Number: 10137 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: Vadim Yanitskiy <axilirator@gmail.com> </div>