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Fuzz exif thumbnail handling #24722

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Merged
ndossche merged 2 commits into from
Oct 28, 2026
Merged

Fuzz exif thumbnail handling #24722

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53ec7fe
Fuzz exif thumbnail handling
yumasansansan Oct 26, 2026
418677b
Store the stream in args[0] directly
yumasansansan Oct 27, 2026
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21 changes: 17 additions & 4 deletions sapi/fuzzer/fuzzer-exif.c
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@
int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
#ifdef HAVE_EXIF
php_stream *stream;
zval stream_zv;
zval args[4];

if (Size > 256 * 1024) {
/* Large inputs have a large impact on fuzzer performance,
Expand All @@ -45,11 +45,24 @@ int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {

stream = php_stream_memory_create(TEMP_STREAM_DEFAULT);
php_stream_write(stream, (const char *) Data, Size);
php_stream_to_zval(stream, &stream_zv);
php_stream_to_zval(stream, &args[0]);

fuzzer_call_php_func_zval("exif_read_data", 1, &stream_zv);
/* exif_read_data($stream, null, false, true): the thumbnail is only read if requested. */
ZVAL_NULL(&args[1]);
ZVAL_FALSE(&args[2]);
ZVAL_TRUE(&args[3]);
fuzzer_call_php_func_zval("exif_read_data", 4, args);

zval_ptr_dtor(&stream_zv);
/* exif_thumbnail($stream, $width, $height, $type): the thumbnail is only scanned for its
* dimensions if they are requested. */
for (int i = 1; i < 4; i++) {
ZVAL_NEW_EMPTY_REF(&args[i]);
ZVAL_NULL(Z_REFVAL(args[i]));
}
fuzzer_call_php_func_zval("exif_thumbnail", 4, args);
for (int i = 0; i < 4; i++) {
zval_ptr_dtor(&args[i]);
}

/* cleanup */
php_request_shutdown(NULL);
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