Changing the on-disk Phar after `mapPhar()` reads incorrect files with the `phar://` protocol

Description

The following code:

<?php

$a = new Phar(__DIR__ . '/a.phar');
$a->addFromString(
	'foo.php',
	<<<'EOT'
		<?php
		echo "this is foo.php\n";
		EOT
);
$a->addFromString(
	'bar.php',
	<<<'EOT'
		<?php
		echo "this is bar.php\n";
		EOT
);
$a->setStub(
	<<<'EOT'
		<?php
		Phar::mapPhar('a.phar');

		include 'phar://a.phar/foo.php';
		rename('b.phar', 'a.phar');
		include 'phar://a.phar/bar.php';
		__HALT_COMPILER(); ?>
		EOT
);

$a = new Phar(__DIR__ . '/b.phar');
$a->addFromString(
	'bar.php',
	<<<'EOT'
		<?php
		/* Shift the offsets compared to a.phar. */
		echo "this is bar.php\n";
		EOT
);
$a->addFromString(
	'foo.php',
	<<<'EOT'
		<?php
		echo "this is foo.php\n";
		EOT
);
$a->setStub(
	<<<'EOT'
		<?php
		Phar::mapPhar('b.phar');

		include 'phar://b.phar/foo.php';
		rename('a.phar', 'b.phar');
		include 'phar://b.phar/bar.php';
		__HALT_COMPILER(); ?>
		EOT
);

Running php a.phar resulted in this output:

this is foo.php
PHP Parse error:  Unterminated comment starting line 2 in phar:///*redacted*/a.phar/bar.php on line 2

But I expected this output instead:

this is foo.php
this is bar.php

The reason for this appears to be that the file offsets and lengths are cached during the mapPhar(), but each time the phar is opened with phar://X.phar it is reopened from disk without validating that it's still the same phar / instead of reopening it from a cached file descriptor.

openat(AT_FDCWD, "*redacted*/a.phar", O_RDONLY) = 4
fstat(4, {st_mode=S_IFREG|0664, st_size=343, ...}) = 0
lseek(4, 0, SEEK_CUR)                   = 0
lseek(4, 0, SEEK_SET)                   = 0
read(4, "<?php\nPhar::mapPhar('a.phar');\n\n"..., 8192) = 343
read(4, "", 8192)                       = 0
lseek(4, 144, SEEK_SET)                 = 144
read(4, " ?>\r\nX\0\0\0\2\0\0\0\21\0\0\0\1\0\0\0\0\0\0\0\0\0\7\0\0\0b"..., 8192) = 199
lseek(4, 149, SEEK_SET)                 = 149
read(4, "X\0\0\0\2\0\0\0\21\0\0\0\1\0\0\0\0\0\0\0\0\0\7\0\0\0bar.ph"..., 8192) = 194
lseek(4, -8, SEEK_END)                  = 335
read(4, "\3\0\0\0GBMB", 8192)           = 8
lseek(4, -40, SEEK_END)                 = 303
read(4, "\250\267o[\342\272\367\303\221>\361\307kf&\257\376\335\360;\356=`\244\270#\335\353\277\253\345$"..., 8192) = 40
lseek(4, 0, SEEK_SET)                   = 0
read(4, "<?php\nPhar::mapPhar('a.phar');\n\n"..., 8192) = 343
ioctl(3, TCGETS, 0x7ffc358e61c0)        = -1 ENOTTY (Inappropriate ioctl for device)
fstat(3, {st_mode=S_IFREG|0664, st_size=343, ...}) = 0
fstat(3, {st_mode=S_IFREG|0664, st_size=343, ...}) = 0
read(3, "<?php\nPhar::mapPhar('a.phar');\n\n"..., 4096) = 343
lseek(4, 272, SEEK_SET)                 = 272
read(4, "<?php\necho \"this is foo.php\\n\";\250"..., 8192) = 71
close(4)                                = 0
write(1, "this is foo.php\n", 16this is foo.php
)       = 16
rename("b.phar", "a.phar")              = 0
newfstatat(AT_FDCWD, "*redacted*/a.phar", {st_mode=S_IFREG|0664, st_size=387, ...}, AT_SYMLINK_NOFOLLOW) = 0
newfstatat(AT_FDCWD, "*redacted*", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0
newfstatat(AT_FDCWD, "*redacted*", {st_mode=S_IFDIR|0775, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0
newfstatat(AT_FDCWD, "*redacted*", {st_mode=S_IFDIR|0755, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0
newfstatat(AT_FDCWD, "*redacted*", {st_mode=S_IFDIR|0755, st_size=4096, ...}, AT_SYMLINK_NOFOLLOW) = 0
openat(AT_FDCWD, "*redacted*/a.phar", O_RDONLY) = 4
fstat(4, {st_mode=S_IFREG|0664, st_size=387, ...}) = 0
lseek(4, 0, SEEK_CUR)                   = 0
lseek(4, 241, SEEK_SET)                 = 241
read(4, "<?php\n/* Shift the offsets compa"..., 8192) = 146
close(4)                                = 0
write(2, "PHP Parse error:  Unterminated c"..., 122PHP Parse error:  Unterminated comment starting line 2 in phar://*redacted*/a.phar/bar.php on line 2
) = 122
close(3)                                = 0

This is an issue for self-updating phars where the autoloader needs to load a class after the update has been performed.

PHP Version

PHP 8.3.14

Operating System

Ubuntu 24.04