fix(#6671): fix possible stack buffer overflow in gen-s-parser.inc (#6678)

The stack buffer overflow is occurring because memcpy(buf, op.data(),
op.size()); can write up to op.size() bytes into buf, but buf is only 33
bytes long. If op.size() is greater than 33, this will result in a
buffer overflow.

1 files changed, 6 insertions, 0 deletions

diff --git a/scripts/gen-s-parser.py b/scripts/gen-s-parser.py
index d75be7635..2aa158c59 100755
--- a/scripts/gen-s-parser.py
+++ b/scripts/gen-s-parser.py
@@ -708,6 +708,10 @@ def instruction_parser():
 
     printer.print_line("auto op = *keyword;")
     printer.print_line("char buf[{}] = {{}};".format(inst_length + 1))
+    printer.print_line("// Ensure we do not copy more than the buffer can hold")
+    printer.print_line("if (op.size() >= sizeof(buf)) {")
+    printer.print_line("  goto parse_error;")
+    printer.print_line("}")
     printer.print_line("memcpy(buf, op.data(), op.size());")
 
     def print_leaf(expr, inst):
@@ -754,9 +758,11 @@ def instruction_parser():
 def print_header():
     print("// DO NOT EDIT! This file generated by scripts/gen-s-parser.py\n")
     print("// clang-format off\n")
+    print("// NOLINTBEGIN\n")
 
 
 def print_footer():
+    print("\n// NOLINTEND")
     print("\n// clang-format on")