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LibC: Stop stdio from adding null terminators out of bounds (#685)

When using the bounded string operations (e.g. snprintf), the null
terminator was always being written even if there was no space for
it (or indeed any valid buffer at all)

This overwriting caused segmentation faults and memory corruption
Vincent Sanders 5 年之前
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1be4c6e9cf
共有 1 个文件被更改,包括 3 次插入3 次删除
  1. 3 3
      Libraries/LibC/stdio.cpp

+ 3 - 3
Libraries/LibC/stdio.cpp

@@ -395,7 +395,6 @@ int sprintf(char* buffer, const char* fmt, ...)
     va_list ap;
     va_start(ap, fmt);
     int ret = vsprintf(buffer, fmt, ap);
-    buffer[ret] = '\0';
     va_end(ap);
     return ret;
 }
@@ -413,7 +412,9 @@ int vsnprintf(char* buffer, size_t size, const char* fmt, va_list ap)
 {
     __vsnprintf_space_remaining = size;
     int ret = printf_internal(sized_buffer_putch, buffer, fmt, ap);
-    buffer[ret] = '\0';
+    if (__vsnprintf_space_remaining) {
+	    buffer[ret] = '\0';
+    }
     return ret;
 }
 
@@ -422,7 +423,6 @@ int snprintf(char* buffer, size_t size, const char* fmt, ...)
     va_list ap;
     va_start(ap, fmt);
     int ret = vsnprintf(buffer, size, fmt, ap);
-    buffer[ret] = '\0';
     va_end(ap);
     return ret;
 }