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Fix fseek undefined behavior #20965

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Fix fseek undefined behavior #20965

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5f49264
Fix fseek undefined behavior
arshidkv12 Jan 18, 2026
69b4e6d
Fix fseek undefined behavior
arshidkv12 Jan 18, 2026
40c76b2
Fix fseek undefined behavior
arshidkv12 Jan 19, 2026
015fc48
Fix fseek undefined behavior
arshidkv12 Jan 19, 2026
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5 changes: 5 additions & 0 deletions main/streams/memory.c
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,11 @@ static int php_stream_memory_seek(php_stream *stream, zend_off_t offset, int whe
php_stream_memory_data *ms = (php_stream_memory_data*)stream->abstract;
assert(ms != NULL);

if (offset == ZEND_LONG_MIN) {
zend_argument_value_error(2, "must be greater than " ZEND_LONG_FMT, ZEND_LONG_MIN);
return FAILURE;
}

switch(whence) {
case SEEK_CUR:
if (offset < 0) {
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15 changes: 15 additions & 0 deletions tests/basic/bug20964.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
--TEST--
Bug #20964 fseek with PHP_INT_MIN on php://memory
--FILE--
<?php
$stream = fopen('php://memory', 'r+');

$result = fseek($stream, PHP_INT_MIN, SEEK_END);
var_dump($result);
?>
--EXPECTF--
Fatal error: Uncaught ValueError: fseek(): Argument #2 ($offset) must be greater than -%d in %s:%d
Stack trace:
#0 %s(%d): fseek(Resource id #%d, -%d, %d)
#1 {main}
thrown in %s on line %d
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