tlv_put: guard against NULL val and 0 len
For example encode_auth_info() from gsup.c calls
msgb_tlv_put(msg, iei, 0, NULL)
to put a tag and len with content data following later.
However, this would cause a memcpy() from a NULL pointer, in tlv_put(). Allow
passing NULL and len = 0 for cases like the above:
If val is NULL, use memset(0) instead of memcpy().
If len is zero, do not copy nor memset anything.
Hence make tlv_put() behave in a well-defined and valid way for any and all
input args; no negative fallout is possible from this patch.
Add proper API doc comment.
Fixes a sanitizer build failure in gsup_test:
../../../../src/libosmocore/include/osmocom/gsm/tlv.h:99:2: runtime error: null pointer passed as argument 2, which is declared to never be null
Helps fix sanitizer build on debian 9.
Change-Id: I13dce9cd1228817890d3e81edeeb660c893c1d64
diff --git a/include/osmocom/gsm/tlv.h b/include/osmocom/gsm/tlv.h
index 5bf4a87..8654893 100644
--- a/include/osmocom/gsm/tlv.h
+++ b/include/osmocom/gsm/tlv.h
@@ -90,13 +90,24 @@
return buf + len;
}
-/*! put (append) a TLV field */
+/*! Append a TLV field, a Tag-Length-Value field.
+ * \param[out] buf Location in a buffer to append TLV at.
+ * \param[in] tag Tag id to write.
+ * \param[in] len Length field to write and amount of bytes to append.
+ * \param[in] val Pointer to data to append, or NULL to append zero data.
+ * Always append tag and length. Append \a len bytes read from \a val. If val is NULL, append \a len zero
+ * bytes instead. If \a len is zero, do not append any data apart from tag and length. */
static inline uint8_t *tlv_put(uint8_t *buf, uint8_t tag, uint8_t len,
const uint8_t *val)
{
*buf++ = tag;
*buf++ = len;
- memcpy(buf, val, len);
+ if (len) {
+ if (val)
+ memcpy(buf, val, len);
+ else
+ memset(buf, 0, len);
+ }
return buf + len;
}