Use open instead of fopen to avoid calls to malloc

Signed-off-by: Giuliano Belinassi <[email protected]>

lib/ulp.c

@@ -88,30 +88,31 @@ begin(void)
   msgq_push("libpulp loaded...\n");
 }
 
-/** @brief Attempt to get FILE pointer to /proc/self/mem
+/** @brief Attempt to get file descriptor to /proc/self/mem
  *
  * Chroots may change the path to the /proc folder.  This function attempts to
  * discover it.
  *
  * @return file pointer.
  */
-FILE *
+int
 get_proc_mem(void)
 {
-  FILE *file = fopen("/proc/self/mem", "r+");
+  int fd = open("/proc/self/mem", O_WRONLY);
 
   /* SLE have some processes which chroots into /proc.  If the above fopen
      fails then try this to check if this is the case.  */
-  if (file == NULL && errno == ENOENT) {
+  if (fd < 0 && errno == ENOENT) {
     /* Process has chroot'ed.  Check if it was chroot'ed to /proc itself.  */
-    file = fopen("/self/mem", "r+");
+    fd = open("/self/mem", O_WRONLY);
   }
 
-  if (file == NULL) {
+  if (fd < 0) {
     WARN("Attempting to open /proc/self/mem failed: %s", libpulp_strerror(errno));
+    set_libpulp_error_state(EPROCMEM);
   }
 
-  return file;
+  return fd;
 }
 
 /** @brief Write into memory bypassing memory protections
@@ -128,14 +129,18 @@ get_proc_mem(void)
 void *
 memwrite(void *dest, const void *src, size_t n)
 {
-  FILE *file = get_proc_mem();
-  libpulp_assert(file);
+  int fd = get_proc_mem();
+  off_t dst = (off_t) dest;
 
-  libpulp_assert(fseek(file, (size_t)dest, SEEK_SET) == 0);
-  libpulp_assert(fwrite(src, 1, n, file) == n);
+  if (fd < 0) {
+    return NULL;
+  }
 
-  fflush(file);
-  fclose(file);
+  libpulp_assert(lseek(fd, dst, SEEK_SET) == dst);
+  libpulp_assert(write(fd, src, n) == (ssize_t) n);
+
+  fsync(fd);
+  close(fd);
 
   return dest;
 }