util: Fix and replace nullvec2str utility function with concatenate()

Multiple issues were found and fixed in previously-unused nullvec2str
function, including major problem with possible stack corruption via
long parameters.

This commit completely rewrites the function to dynamically resize the
buffer while appending new parameters to avoid previous problems.

Additionally, name is changed to somewhat more developer friendly name.

Influenced-by: Mateusz Mościcki and Michał Bloch
Change-Id: Ia97e3851bb4b5779a14704098752e3644c487f0b

diff --git a/src/shared/util.c b/src/shared/util.c
index 775d6be..bdb8259 100644 (file)
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -828,17 +828,34 @@ char* get_exe_path(pid_t pid)
        return result;
 }
 
-char *nullvec2str(char *const vec[])
+/* This function is supposed to accept same data as passed to execve
+ * (argv and envp), which can be arrays of strings as well as NULL
+ * pointer.
+ */
+char* concatenate(char *const vec[])
 {
-       char command[PATH_MAX] = {0, };
+       size_t length = 0;
+       for (char *const *p = vec; p && *p; p++)
+               length += strlen(*p) + 1;
+
+       if (length == 0)
+               return strdup("");
+
+       char *str = (char *)malloc(length);
+       if (!str)
+               return NULL;
 
-       for (char *const *p = vec; *p; ++p) {
-               strncat(command, *p, sizeof(command)-1);
-               strncat(command, " ", sizeof(command)-1);
+       char *destp = str;
+       char *const *vecp = vec;
+       while (*vecp) {
+               destp = stpcpy(destp, *(vecp++));
+               if (*vecp)
+                       destp = stpcpy(destp, " ");
        }
-       command[sizeof(command)-1] = 0;
-       return strdup(command);
+
+       return str;
 }
+
 /**
  * @}
  */

diff --git a/src/shared/util.h b/src/shared/util.h
index dfe40bf..53e0c7d 100644 (file)
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -67,7 +67,7 @@ char* get_exe_path(pid_t pid);
 
 char* get_cmd_line(pid_t pid);
 
-char *nullvec2str(char *const vec[]);
+char* concatenate(char *const vec[]);
 
 #ifdef __cplusplus
 }