i2c: fix dereference beyond the end of buffer

Print the contents of the buffer as an array of bytes in hex, which
avoids endian issues and reading beyond the end of the buffer.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

core/i2c.c

@@ -138,6 +138,8 @@ int64_t i2c_request_sync(struct i2c_request *req)
 	uint64_t timer_period = msecs_to_tb(5), timer_count;
 	uint64_t time_to_wait = 0;
 	int64_t rc, waited, retries;
+	size_t i, count;
+	char buf[17]; /* 8 bytes in hex + NUL */
 
 	for (retries = 0; retries <= MAX_NACK_RETRIES; retries++) {
 		waited = 0;
@@ -175,10 +177,16 @@ int64_t i2c_request_sync(struct i2c_request *req)
 		req->req_state = i2c_req_new;
 	}
 
-	prlog(PR_DEBUG, "I2C: %s req op=%x offset=%x buf=%016llx buflen=%d "
+	count = 0;
+	for (i = 0; i < req->rw_len && count < sizeof(buf); i++) {
+		count += snprintf(buf+count, sizeof(buf)-count, "%02x",
+				*(unsigned char *)(req->rw_buf+i));
+	}
+
+	prlog(PR_DEBUG, "I2C: %s req op=%x offset=%x buf=%s buflen=%d "
 	      "delay=%lu/%lld rc=%lld\n",
 	      (rc) ? "!!!!" : "----", req->op, req->offset,
-	      *(uint64_t*) req->rw_buf, req->rw_len, tb_to_msecs(waited), req->timeout, rc);
+	      buf, req->rw_len, tb_to_msecs(waited), req->timeout, rc);
 
 	return rc;
 }