Description:
------------
OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=19044

Valgrind:

==12951== Invalid read of size 1
==12951==    at 0x4C335B8: __strncmp_sse42 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==12951==    by 0x533ECF: exif_process_IFD_in_MAKERNOTE (exif.c:3168)
==12951==    by 0x535852: exif_process_IFD_TAG (exif.c:3547)
==12951==    by 0x537787: exif_process_IFD_in_TIFF (exif.c:4219)
==12951==    by 0x537D1B: exif_scan_FILE_header (exif.c:4316)
==12951==    by 0x5385F2: exif_read_from_impl (exif.c:4427)
==12951==    by 0x53866D: exif_read_from_stream (exif.c:4444)
==12951==    by 0x53873A: exif_read_from_file (exif.c:4471)
==12951==    by 0x538FB2: zif_exif_read_data (exif.c:4544)
==12951==    by 0xA7D72F: ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER (zend_vm_execute.h:621)
==12951==    by 0xB040D0: execute_ex (zend_vm_execute.h:59766)
==12951==    by 0xB094CF: zend_execute (zend_vm_execute.h:63792)
==12951==  Address 0x1088dd5e is 0 bytes after a block of size 30 alloc'd
==12951==    at 0x4C31D2F: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==12951==    by 0x9DE192: __zend_realloc (zend_alloc.c:2851)
==12951==    by 0x9DD53B: _erealloc (zend_alloc.c:2466)
==12951==    by 0x9DD773: _safe_erealloc (zend_alloc.c:2505)
==12951==    by 0x531343: exif_file_sections_realloc (exif.c:2045)
==12951==    by 0x536D3A: exif_process_IFD_in_TIFF (exif.c:4059)
==12951==    by 0x537D1B: exif_scan_FILE_header (exif.c:4316)
==12951==    by 0x5385F2: exif_read_from_impl (exif.c:4427)
==12951==    by 0x53866D: exif_read_from_stream (exif.c:4444)
==12951==    by 0x53873A: exif_read_from_file (exif.c:4471)
==12951==    by 0x538FB2: zif_exif_read_data (exif.c:4544)
==12951==    by 0xA7D72F: ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER (zend_vm_execute.h:621)
==12951== 

Test script:
---------------
<?php
  
var_dump(exif_read_data('data:image/jpg;base64,TU0AKgAAAAwgICAgAAIBDwAEAAAAAgAAACKSfCAgAAAAAEZVSklGSUxN'));