Fix a possible integer overflow

CHANGELOG.md

@@ -94,6 +94,8 @@ and this project adheres to
   - [#1572](https://github.com/iovisor/bpftrace/pull/1572)
 - Check string comparison size
   - [#1573](https://github.com/iovisor/bpftrace/pull/1573)
+- Fix a possible integer overflow
+  - [#1580](https://github.com/iovisor/bpftrace/pull/1580)
 
 #### Tools
 - Hook up execsnoop.bt script onto `execveat` call

src/clang_parser.cpp

@@ -221,8 +221,19 @@ static bool getBitfield(CXCursor c, Bitfield &bitfield)
 
   size_t bitfield_offset = clang_Cursor_getOffsetOfField(c) % 8;
   size_t bitfield_bitwidth = clang_getFieldDeclBitWidth(c);
+  size_t bitfield_bitdidth_max = sizeof(uint64_t) * 8;
 
-  bitfield.mask = (1 << bitfield_bitwidth) - 1;
+  if (bitfield_bitwidth > bitfield_bitdidth_max)
+  {
+    LOG(WARNING) << "bitfiled bitwidth " << bitfield_bitwidth
+                 << "is not supporeted."
+                 << " Use bitwidth " << bitfield_bitdidth_max;
+    bitfield_bitwidth = bitfield_bitdidth_max;
+  }
+  if (bitfield_bitwidth == bitfield_bitdidth_max)
+    bitfield.mask = std::numeric_limits<uint64_t>::max();
+  else
+    bitfield.mask = (1ULL << bitfield_bitwidth) - 1;
   bitfield.access_rshift = bitfield_offset;
   // Round up to nearest byte
   bitfield.read_bytes = (bitfield_offset + bitfield_bitwidth + 7) / 8;

src/struct.h

@@ -15,7 +15,7 @@ struct Bitfield
   // Then rshift the resulting value by `access_rshift` to get field value
   size_t access_rshift;
   // Then logical AND `mask` to mask out everything but this bitfield
-  size_t mask;
+  uint64_t mask;
 };
 
 struct Field