[Bug libfortran/62094] New: Program crash when executing DEALLOCATE with addresses that have 0 in bits 26 and higher (little-endian)

[shamsundar at uh dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62094

            Bug ID: 62094
           Summary: Program crash when executing DEALLOCATE with addresses
                    that have 0 in bits 26 and higher (little-endian)
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shamsundar at uh dot edu

Created attachment 33293
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33293&action=edit
Fortran program that will exhibit the bug on a Linux x86-64 system, eg.
openSuse 12.3 desktop

The library routine free() in libc.so.6 on some X86-64 Linux systems will
deference address zero when the argument has bits 26 and up all zero. This will
cause the program to crash. A Fortran program that exposes this bug is
attached. Here are a few instructions from free(), from libc.so.6, stable
release 2.17, configured for x86_64_linux, gcc 4.7.2:

__libc_free: (argument in %rdi)
...
   7ea08:       48 8d 77 f0             lea    -0x10(%rdi),%rsi
...
   7ea1b:       48 89 f0                mov    %rsi,%rax
   7ea1e:       48 25 00 00 00 fc       and    $0xfffffffffc000000,%rax
   7ea24:       48 8b 38                mov    (%rax),%rdi            <<<====
crash if %rax =  0