[llvm-readelf] - Do not read past the end of file when dumping SHT_GNU_HASH.

[grimar]

Summary

We have unobvious issue in the condition that is used to check
that we do not read past the EOF.

The problem is that the result of "GnuHashTable->nbuckets * 4" expression is uint32.
Because of that it was still possible to overflow it and pass the check.

There was no such problem with the "GnuHashTable->maskwords * sizeof(typename ELFT::Off)"
condition, because of sizeof on the right (which gives 64-bits value on x64),
but I've added an explicit conversion to 64-bit value for GnuHashTable->maskwords too.

[MaskRay]

Do not try to read past the end of the file when dumping the the SHT_GNU_HASH.

Do not read past the end of file when dumping SHT_GNU_HASH?

[grimar]

In D81103#2072024, @MaskRay wrote:

Do not try to read past the end of the file when dumping the the SHT_GNU_HASH.

Do not read past the end of file when dumping SHT_GNU_HASH?

Thanks!

[jhenderson]

LGTM too.

llvm/test/tools/llvm-readobj/ELF/hash-histogram.test

Sections:
       - Section: .hash
       - Section: .gnu.hash
       - Section: .dynamic
 
 ## Check we report a proper warning when the GNU hash table goes past the end of the file.
 
 ## Case A: the 'nbuckets' field is set so that the GNU hash table goes past the end of the file.
 ##         The value of 1 for the NBUCKETS is no-op.
-# RUN: yaml2obj --docnum=6 -D MASKWORDS=4294967295 -D NBUCKETS=1 %s -o %t7
+# RUN: yaml2obj --docnum=6 -D MASKWORDS=0x80000000 -D NBUCKETS=1 %s -o %t7
 # RUN: llvm-readelf --elf-hash-histogram %t7 2>&1 | \
 # RUN:   FileCheck %s -DFILE=%t7 --check-prefix=ERR5 --implicit-check-not="Histogram"
 
 # ERR5: warning: '[[FILE]]': unable to dump the SHT_GNU_HASH section at 0x78: it goes past the end of the file
 
 ## Case B: the 'maskwords' field is set so that the GNU hash table goes past the end of the file.
 ##         The value of 1 for the MASKWORDS is no-op.
-# RUN: yaml2obj --docnum=6 -D MASKWORDS=1 -D NBUCKETS=4294967295 %s -o %t8
+# RUN: yaml2obj --docnum=6 -D MASKWORDS=1 -D NBUCKETS=0x80000000 %s -o %t8
 # RUN: llvm-readelf --elf-hash-histogram %t8 2>&1 | \
 # RUN:   FileCheck %s -DFILE=%t8 --check-prefix=ERR5 --implicit-check-not="Histogram"
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_DYN

llvm/tools/llvm-readobj/ELFDumper.cpp

static Error checkGNUHashTable(const ELFFile<ELFT> *Obj,
   const uint8_t *TableData = reinterpret_cast<const uint8_t *>(GnuHashTable);
   assert(TableData >= Obj->base() &&
          TableData < Obj->base() + Obj->getBufSize() &&
          "GnuHashTable must always point to a location inside the file");
 
   uint64_t TableOffset = TableData - Obj->base();
   if (IsHeaderValid)
     *IsHeaderValid = TableOffset + /*Header size:*/ 16 < Obj->getBufSize();
-  if (TableOffset + 16 + GnuHashTable->nbuckets * 4 +
-          GnuHashTable->maskwords * sizeof(typename ELFT::Off) >=
+  if (TableOffset + 16 + (uint64_t)GnuHashTable->nbuckets * 4 +
+          (uint64_t)GnuHashTable->maskwords * sizeof(typename ELFT::Off) >=
       Obj->getBufSize())
     return createError("unable to dump the SHT_GNU_HASH "
                        "section at 0x" +
                        Twine::utohexstr(TableOffset) +
                        ": it goes past the end of the file");
   return Error::success();
 }