realloc: use Curl_saferealloc to avoid common mistakes

Discussed: https://curl.haxx.se/mail/lib-2016-11/0087.html

lib/content_encoding.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -28,8 +28,8 @@
 #include <curl/curl.h>
 #include "sendf.h"
 #include "content_encoding.h"
+#include "strdup.h"
 #include "curl_memory.h"
-
 #include "memdebug.h"
 
 /* Comment this out if zlib is always going to be at least ver. 1.2.0.4
@@ -371,12 +371,9 @@ Curl_unencode_gzip_write(struct connectdata *conn,
   {
     /* Need more gzip header data state */
     ssize_t hlen;
-    unsigned char *oldblock = z->next_in;
-
     z->avail_in += (uInt)nread;
-    z->next_in = realloc(z->next_in, z->avail_in);
+    z->next_in = Curl_saferealloc(z->next_in, z->avail_in);
     if(z->next_in == NULL) {
-      free(oldblock);
       return exit_zlib(z, &k->zlib_init, CURLE_OUT_OF_MEMORY);
     }
     /* Append the new block of data to the previous one */

lib/curl_ntlm_wb.c

@@ -51,6 +51,7 @@
 #include "curl_ntlm_wb.h"
 #include "url.h"
 #include "strerror.h"
+#include "strdup.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
@@ -293,11 +294,10 @@ static CURLcode ntlm_wb_response(struct connectdata *conn,
       buf[len_out - 1] = '\0';
       break;
     }
-    newbuf = realloc(buf, len_out + NTLM_BUFSIZE);
-    if(!newbuf) {
-      free(buf);
+    newbuf = Curl_saferealloc(buf, len_out + NTLM_BUFSIZE);
+    if(!newbuf)
       return CURLE_OUT_OF_MEMORY;
-    }
+
     buf = newbuf;
   }
 

lib/escape.c

@@ -31,6 +31,7 @@
 #include "warnless.h"
 #include "non-ascii.h"
 #include "escape.h"
+#include "strdup.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
@@ -109,11 +110,9 @@ char *curl_easy_escape(struct Curl_easy *data, const char *string,
       newlen += 2; /* the size grows with two, since this'll become a %XX */
       if(newlen > alloc) {
         alloc *= 2;
-        testing_ptr = realloc(ns, alloc);
-        if(!testing_ptr) {
-          free(ns);
+        testing_ptr = Curl_saferealloc(ns, alloc);
+        if(!testing_ptr)
           return NULL;
-        }
         else {
           ns = testing_ptr;
         }

lib/http.c

@@ -76,6 +76,7 @@
 #include "pipeline.h"
 #include "http2.h"
 #include "connect.h"
+#include "strdup.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -1255,14 +1256,13 @@ CURLcode Curl_add_buffer(Curl_send_buffer *in, const void *inptr, size_t size)
 
     if(in->buffer)
       /* we have a buffer, enlarge the existing one */
-      new_rb = realloc(in->buffer, new_size);
+      new_rb = Curl_saferealloc(in->buffer, new_size);
     else
       /* create a new buffer */
       new_rb = malloc(new_size);
 
     if(!new_rb) {
       /* If we failed, we cleanup the whole buffer and return error */
-      Curl_safefree(in->buffer);
       free(in);
       return CURLE_OUT_OF_MEMORY;
     }

lib/http2.c

@@ -35,7 +35,7 @@
 #include "url.h"
 #include "connect.h"
 #include "strtoofft.h"
-
+#include "strdup.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
@@ -841,10 +841,9 @@ static int on_header(nghttp2_session *session, const nghttp2_frame *frame,
             stream->push_headers_alloc) {
       char **headp;
       stream->push_headers_alloc *= 2;
-      headp = realloc(stream->push_headers,
+      headp = Curl_saferealloc(stream->push_headers,
                                stream->push_headers_alloc * sizeof(char *));
       if(!headp) {
-        free(stream->push_headers);
         stream->push_headers = NULL;
         return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
       }

lib/rtsp.c

@@ -36,6 +36,7 @@
 #include "strcase.h"
 #include "select.h"
 #include "connect.h"
+#include "strdup.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
@@ -614,9 +615,9 @@ static CURLcode rtsp_rtp_readwrite(struct Curl_easy *data,
 
   if(rtspc->rtp_buf) {
     /* There was some leftover data the last time. Merge buffers */
-    char *newptr = realloc(rtspc->rtp_buf, rtspc->rtp_bufsize + *nread);
+    char *newptr = Curl_saferealloc(rtspc->rtp_buf,
+                                    rtspc->rtp_bufsize + *nread);
     if(!newptr) {
-      Curl_safefree(rtspc->rtp_buf);
       rtspc->rtp_buf = NULL;
       rtspc->rtp_bufsize = 0;
       return CURLE_OUT_OF_MEMORY;

lib/security.c

@@ -62,7 +62,7 @@
 #include "sendf.h"
 #include "strcase.h"
 #include "warnless.h"
-
+#include "strdup.h"
 /* The last #include file should be: */
 #include "memdebug.h"
 
@@ -202,7 +202,7 @@ static CURLcode read_data(struct connectdata *conn,
   if(len) {
     /* only realloc if there was a length */
     len = ntohl(len);
-    tmp = realloc(buf->data, len);
+    tmp = Curl_saferealloc(buf->data, len);
   }
   if(tmp == NULL)
     return CURLE_OUT_OF_MEMORY;

lib/ssh.c

@@ -71,7 +71,7 @@
 #include "url.h"
 #include "speedcheck.h"
 #include "getinfo.h"
-
+#include "strdup.h"
 #include "strcase.h"
 #include "vtls/vtls.h"
 #include "connect.h"
@@ -2112,9 +2112,10 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
 
       /* get room for the filename and extra output */
       sshc->readdir_totalLen += 4 + sshc->readdir_len;
-      new_readdir_line = realloc(sshc->readdir_line, sshc->readdir_totalLen);
+      new_readdir_line = Curl_saferealloc(sshc->readdir_line,
+                                          sshc->readdir_totalLen);
       if(!new_readdir_line) {
-        Curl_safefree(sshc->readdir_line);
+        sshc->readdir_line = NULL;
         Curl_safefree(sshc->readdir_filename);
         Curl_safefree(sshc->readdir_longentry);
         state(conn, SSH_SFTP_CLOSE);

lib/strdup.c

@@ -75,3 +75,26 @@ void *Curl_memdup(const void *src, size_t length)
 
   return buffer;
 }
+
+/***************************************************************************
+ *
+ * Curl_saferealloc(ptr, size)
+ *
+ * Does a normal realloc(), but will free the data pointer if the realloc
+ * fails. If 'size' is zero, it will free the data and return a failure.
+ *
+ * This convenience function is provided and used to help us avoid a common
+ * mistake pattern when we could pass in a zero, catch the NULL return and end
+ * up free'ing the memory twice.
+ *
+ * Returns the new pointer or NULL on failure.
+ *
+ ***************************************************************************/
+void *Curl_saferealloc(void *ptr, size_t size)
+{
+  void *datap = realloc(ptr, size);
+  if(size && !datap)
+    /* only free 'ptr' if size was non-zero */
+    free(ptr);
+  return datap;
+}

lib/strdup.h

@@ -27,5 +27,6 @@
 extern char *curlx_strdup(const char *str);
 #endif
 void *Curl_memdup(const void *src, size_t buffer_length);
+void *Curl_saferealloc(void *ptr, size_t size);
 
 #endif /* HEADER_CURL_STRDUP_H */