From e750980d6c89cf7052daa62745366a743badd384 Mon Sep 17 00:00:00 2001 From: Neels Hofmeyr Date: Thu, 16 Nov 2017 23:34:33 +0100 Subject: 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 --- include/osmocom/gsm/tlv.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/include/osmocom/gsm/tlv.h b/include/osmocom/gsm/tlv.h index 5bf4a87b..8654893b 100644 --- a/include/osmocom/gsm/tlv.h +++ b/include/osmocom/gsm/tlv.h @@ -90,13 +90,24 @@ static inline uint8_t *lv_put(uint8_t *buf, uint8_t len, 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; } -- cgit v1.2.3