Fixed google::FindSymbol reading past end of a section

base/third_party/symbolize/symbolize.cc

 // Copyright (c) 2006, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 278 matching lines @@
     // 32 elements (to keep stack consumption low), otherwise we can
     // have a 64 element Elf32_Sym array.
 #if __WORDSIZE == 64
 #define NUM_SYMBOLS 32
 #else
 #define NUM_SYMBOLS 64
 #endif
 
     // Read at most NUM_SYMBOLS symbols at once to save read() calls.
     ElfW(Sym) buf[NUM_SYMBOLS];
-    const ssize_t len = ReadFromOffset(fd, &buf, sizeof(buf), offset);
+    int num_symbols_to_read = num_symbols - i;

[hamaji, 2016/12/16 07:21:14]

Use std::min?

+    if (num_symbols_to_read > NUM_SYMBOLS)
+      num_symbols_to_read = NUM_SYMBOLS;
+    const ssize_t len =
+        ReadFromOffset(fd, &buf, sizeof(buf[0]) * num_symbols_to_read, offset);
     SAFE_ASSERT(len % sizeof(buf[0]) == 0);
     const ssize_t num_symbols_in_buf = len / sizeof(buf[0]);
-    SAFE_ASSERT(num_symbols_in_buf <= sizeof(buf)/sizeof(buf[0]));
+    SAFE_ASSERT(num_symbols_in_buf <= num_symbols_to_read);
     for (int j = 0; j < num_symbols_in_buf; ++j) {
       const ElfW(Sym)& symbol = buf[j];
       uint64_t start_address = symbol.st_value;
       start_address += symbol_offset;
       uint64_t end_address = start_address + symbol.st_size;
       if (symbol.st_value != 0 &&  // Skip null value symbols.
           symbol.st_shndx != 0 &&  // Skip undefined symbols.
           start_address <= pc && pc < end_address) {
         ssize_t len1 = ReadFromOffset(fd, out, out_size,
                                       strtab->sh_offset + symbol.st_name);
@@ skipping 548 matching lines @@
 
 // TODO: Support other environments.
 bool Symbolize(void *pc, char *out, int out_size) {
   assert(0);
   return false;
 }
 
 _END_GOOGLE_NAMESPACE_
 
 #endif