Description of problem:
An issue was discovered in pspp 1.2.0. There is a buffer overflow at function read_bytes_internal, will leads to denial of service.

Version-Release number of selected component (if applicable):
pspp 1.2.0, pspp-dump-sav

How reproducible:
run in shell
$ pspp-dump-sav poc

Actual results:
crash


Additional info:
asan report
```
=================================================================
==6378==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000011 at pc 0x00000049beec bp 0x7ffc260fd5f0 sp 0x7ffc260fcda0
WRITE of size 199 at 0x602000000011 thread T0
    #0 0x49beeb in __interceptor_fread.part.47 /home/pwd/llvm_dev/llvm/projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:978
    #1 0x52605c in read_bytes_internal /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/utilities/pspp-dump-sav.c:1585:23
    #2 0x52605c in read_bytes /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/utilities/pspp-dump-sav.c:1601
    #3 0x52605c in open_text_record /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/utilities/pspp-dump-sav.c:1399
    #4 0x51f39d in read_long_var_name_map /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/utilities/pspp-dump-sav.c:912:10
    #5 0x51f39d in read_extension_record /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/utilities/pspp-dump-sav.c:626
    #6 0x51f39d in main /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/utilities/pspp-dump-sav.c:218
    #7 0x7fc5a43a4b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #8 0x41a4c9 in _start (/home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/installed-asan/bin/pspp-dump-sav+0x41a4c9)

0x602000000011 is located 0 bytes to the right of 1-byte region [0x602000000010,0x602000000011)
allocated by thread T0 here:
    #0 0x4da380 in malloc /home/pwd/llvm_dev/llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:88
    #1 0x52bb7d in xmalloc /home/pwd/fuzz/fuzz-pspp/pspp-1.2.0/gl/xmalloc.c:41:13
    #2 0x61600000007f  (<unknown module>)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/pwd/llvm_dev/llvm/projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:978 in __interceptor_fread.part.47
Shadow bytes around the buggy address:
  0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa[01]fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==6378==ABORTING

```

gdb info

```
   1582	 read_bytes_internal (struct sfm_reader *r, bool eof_is_ok,
   1583	                      void *buf, size_t byte_cnt)
   1584	 {
 → 1585	   size_t bytes_read = fread (buf, 1, byte_cnt, r->file);
   1586	   if (bytes_read == byte_cnt)
   1587	     return true;
   1588	   else if (ferror (r->file))
   1589	     sys_error (r, "System error: %s.", strerror (errno));
   1590	   else if (!eof_is_ok || bytes_read != 0)
// buf=0x602000000010, byte_cnt=0xffffffffffffffff
```