<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>. 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<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>