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Fix undefined behavior in php_stream_memory_seek() #21353

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Fix undefined behavior in php_stream_memory_seek() #21353

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58 changes: 58 additions & 0 deletions ext/standard/tests/streams/memory_stream_seek_int_min.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,58 @@
--TEST--
php://memory and php://temp stream seek with PHP_INT_MIN does not trigger undefined behavior
--FILE--
<?php
foreach (['php://memory', 'php://temp'] as $wrapper) {
echo "=== $wrapper ===\n";

$stream = fopen($wrapper, 'r+');
fwrite($stream, 'hello');

// SEEK_CUR with PHP_INT_MIN from middle of stream
fseek($stream, 2, SEEK_SET);
var_dump(fseek($stream, PHP_INT_MIN, SEEK_CUR));

// SEEK_CUR with PHP_INT_MIN from beginning of stream
fseek($stream, 0, SEEK_SET);
var_dump(fseek($stream, PHP_INT_MIN, SEEK_CUR));

// SEEK_END with PHP_INT_MIN
var_dump(fseek($stream, PHP_INT_MIN, SEEK_END));

// Normal negative SEEK_CUR that should succeed
fseek($stream, 4, SEEK_SET);
var_dump(fseek($stream, -2, SEEK_CUR));
var_dump(ftell($stream));

// Normal negative SEEK_END that should succeed
var_dump(fseek($stream, -3, SEEK_END));
var_dump(ftell($stream));

// Verify stream still works after all edge-case seeks
fseek($stream, 0, SEEK_SET);
var_dump(fread($stream, 5));

fclose($stream);
}
echo "Done\n";
?>
--EXPECT--
=== php://memory ===
int(-1)
int(-1)
int(-1)
int(0)
int(2)
int(0)
int(2)
string(5) "hello"
=== php://temp ===
int(-1)
int(-1)
int(-1)
int(0)
int(2)
int(0)
int(2)
string(5) "hello"
Done
4 changes: 2 additions & 2 deletions main/streams/memory.c
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Original file line number Diff line number Diff line change
Expand Up @@ -128,7 +128,7 @@ static int php_stream_memory_seek(php_stream *stream, zend_off_t offset, int whe
switch(whence) {
case SEEK_CUR:
if (offset < 0) {
if (ms->fpos < (size_t)(-offset)) {
if (ms->fpos < (size_t)0 - (size_t)offset) {
ms->fpos = 0;
*newoffs = -1;
return -1;
Expand Down Expand Up @@ -165,7 +165,7 @@ static int php_stream_memory_seek(php_stream *stream, zend_off_t offset, int whe
stream->eof = 0;
stream->fatal_error = 0;
return 0;
} else if (ZSTR_LEN(ms->data) < (size_t)(-offset)) {
} else if (ZSTR_LEN(ms->data) < (size_t)0 - (size_t)offset) {
ms->fpos = 0;
*newoffs = -1;
return -1;
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