Protect against recursive processing of the fat header in MachOImageReader.

chrome/common/safe_browsing/mach_o_image_reader_mac.cc

Index: chrome/common/safe_browsing/mach_o_image_reader_mac.cc
diff --git a/chrome/common/safe_browsing/mach_o_image_reader_mac.cc b/chrome/common/safe_browsing/mach_o_image_reader_mac.cc
index 8d1c946d8f663cd0df15a04895881e07cc7b185c..3ce37516c723e9390373a607536df48e9c402b5b 100644
--- a/chrome/common/safe_browsing/mach_o_image_reader_mac.cc
+++ b/chrome/common/safe_browsing/mach_o_image_reader_mac.cc
@@ -122,6 +122,11 @@ bool MachOImageReader::Initialize(const uint8_t* image, size_t image_size) {
       uint32_t arch_offset = do_swap ? OSSwapInt32(arch->offset) : arch->offset;
       uint32_t arch_size = do_swap ? OSSwapInt32(arch->size) : arch->size;
 
+      // Cannot refer back to headers of previous arches to cause
+      // recursive processing.
+      if (arch_offset < offset)
+        return false;
+
       ByteSlice slice = data_->Slice(arch_offset, arch_size);
       if (!slice.IsValid())
         return false;