[XS] Change in libosmo-sccp[master]: coverity CID#216830

[neels]

neels has uploaded this change for review. ( 
https://gerrit.osmocom.org/c/libosmo-sccp/+/37995?usp=email )


Change subject: coverity CID#216830
......................................................................

coverity CID#216830

sanity-check par->len received on the wire.

Change-Id: I3e6283154268f97a66b2b3f2ec8e3e9631424434
---
M src/sua.c
1 file changed, 5 insertions(+), 1 deletion(-)



  git pull ssh://gerrit.osmocom.org:29418/libosmo-sccp refs/changes/95/37995/1

diff --git a/src/sua.c b/src/sua.c
index 9e281e0..d4c8b29 100644
--- a/src/sua.c
+++ b/src/sua.c
@@ -436,7 +436,11 @@
                par = (struct xua_parameter_hdr *) &param->dat[pos];
                par_tag = ntohs(par->tag);
                par_len = ntohs(par->len);
-               par_datalen = par_len - sizeof(*par);
+               /* sanity: check par->len received on the wire, make sure the 
subtraction does not wrap past zero */
+               if (par_len >= sizeof(*par))
+                       par_datalen = par_len - sizeof(*par);
+               else
+                       par_datalen = 0;

                LOGP(DLSUA, LOGL_DEBUG, "SUA IEI 0x%04x pos %hu/%hu: subpart 
tag 0x%04x, len %hu\n",
                     param->tag, pos, param->len, par_tag, par_len);

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Gerrit-MessageType: newchange
Gerrit-Project: libosmo-sccp
Gerrit-Branch: master
Gerrit-Change-Id: I3e6283154268f97a66b2b3f2ec8e3e9631424434
Gerrit-Change-Number: 37995
Gerrit-PatchSet: 1
Gerrit-Owner: neels <nhofm...@sysmocom.de>