osmo-bts-trx: refactor parse_rsp(), fix compilation warnings

For a long time, we see this annoying -Wstringop-truncation warning:

  In function ‘parse_rsp’,
      inlined from ‘trx_ctrl_read_cb’ at trx_if.c:647:6:
  trx_if.c:416:2: warning: ‘strncat’ output may be truncated copying
                  between 0 and 45 bytes from a string of length 1495
    416 |  strncat(rsp->cmd, buf_in + 4, p - buf_in - 4);
        |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is no real need to use strncat() in parse_rsp(), because we
do not concatenate any strings but simply copy TRXC response parts
from the input buffer to the corresponding 'name' and 'parameters'
buffers.  Let's use memcpy() instead.  This also fixes the warning.

Change-Id: Ia10adf7d76abe9a423b07e828852fbfb53b95125

1 files changed, 20 insertions, 12 deletions

diff --git a/src/osmo-bts-trx/trx_if.c b/src/osmo-bts-trx/trx_if.c
index 18c5011a..ff631874 100644
--- a/src/osmo-bts-trx/trx_if.c
+++ b/src/osmo-bts-trx/trx_if.c
@@ -397,6 +397,7 @@ struct trx_ctrl_rsp {
 
 static int parse_rsp(const char *buf_in, size_t len_in, struct trx_ctrl_rsp *rsp)
 {
+	size_t nlen, plen;
 	char *p, *k;
 
 	if (strncmp(buf_in, "RSP ", 4))
@@ -406,14 +407,17 @@ static int parse_rsp(const char *buf_in, size_t len_in, struct trx_ctrl_rsp *rsp
 	if (!(p = strchr(buf_in + 4, ' ')))
 		goto parse_err;
 
-	if (p - buf_in >= sizeof(rsp->cmd)) {
-		LOGP(DTRX, LOGL_ERROR, "cmd buffer too small %lu >= %zu\n",
-		     (long unsigned) (p - buf_in), sizeof(rsp->cmd));
+	/* Calculate length of the name part */
+	nlen = p - (buf_in + 4);
+
+	if (nlen >= sizeof(rsp->cmd)) {
+		LOGP(DTRX, LOGL_ERROR, "TRXC command name part is too long: "
+		     "%zu >= %zu\n", nlen, sizeof(rsp->cmd));
 		goto parse_err;
 	}
 
-	rsp->cmd[0] = '\0';
-	strncat(rsp->cmd, buf_in + 4, p - buf_in - 4);
+	memcpy(&rsp->cmd[0], buf_in + 4, nlen);
+	rsp->cmd[nlen] = '\0';
 
 	/* Now comes the status code of the response */
 	p++;
@@ -427,18 +431,22 @@ static int parse_rsp(const char *buf_in, size_t len_in, struct trx_ctrl_rsp *rsp
 	else
 		k = p + strlen(p);
 
-	if (strlen(k) >= sizeof(rsp->params)) {
-		LOGP(DTRX, LOGL_ERROR, "params buffer too small %zu >= %zu\n",
-			strlen(k), sizeof(rsp->params));
+	/* Calculate length of the parameters part */
+	plen = strlen(k);
+
+	if (plen >= sizeof(rsp->params)) {
+		LOGP(DTRX, LOGL_ERROR, "TRXC command parameters part is too long: "
+		     "%zu >= %zu\n", plen, sizeof(rsp->params));
 		goto parse_err;
 	}
-	rsp->params[0] = '\0';
-	strcat(rsp->params, k);
+
+	memcpy(&rsp->params[0], k, plen);
+	rsp->params[plen] = '\0';
+
 	return 0;
 
 parse_err:
-	LOGP(DTRX, LOGL_NOTICE, "Unknown message on ctrl port: %s\n",
-		buf_in);
+	LOGP(DTRX, LOGL_NOTICE, "Unknown TRXC message: %s\n", buf_in);
 	return -1;
 }