[php-src] master: Fix use-after-free on re-entrant ftp_close() during a transfer

Author: Ilia Alshanetsky (iliaal)
Date: 2026-07-12T20:55:06-04:00

Commit: https://github.com/php/php-src/commit/1feb20156bbfc4450e455a92a026e5a53eba5937
Raw diff: https://github.com/php/php-src/commit/1feb20156bbfc4450e455a92a026e5a53eba5937.diff

Fix use-after-free on re-entrant ftp_close() during a transfer

A user stream wrapper passed to a blocking or non-blocking FTP transfer can
re-enter the engine from its stream_read/stream_write handler while the
engine still holds the freed ftpbuf_t/databuf_t on the C stack, so the
transfer resumes on freed memory. Guard every operation that opens a data
connection with an in_use flag: ftp_close() throws while it is set, and the
transfer and listing functions refuse to run. The non-blocking checks sit
at the userland entry, before the wrapper mutates ftp->direction/stream, so
a rejected re-entrant call cannot corrupt the outer transfer; the nb cleanup
clears ftp->stream before closing the stream so a stream_close() that calls
ftp_close() cannot double-close it.

Closes GH-22400

Changed paths:
  A  ext/ftp/tests/ftp_close_during_transfer.phpt
  A  ext/ftp/tests/ftp_nb_close_during_transfer.phpt
  A  ext/ftp/tests/ftp_nb_get_during_nb_transfer.phpt
  A  ext/ftp/tests/ftp_nb_get_during_transfer.phpt
  M  ext/ftp/ftp.c
  M  ext/ftp/ftp.h
  M  ext/ftp/php_ftp.c


Diff:

diff --git a/ext/ftp/ftp.c b/ext/ftp/ftp.c
index 17a3e10e0d61..1345e378d8e3 100644
--- a/ext/ftp/ftp.c
+++ b/ext/ftp/ftp.c
@@ -892,6 +892,11 @@ ftp_get(ftpbuf_t *ftp, php_stream *outstream, const char *path, const size_t pat
 	if (ftp == NULL) {
 		return 0;
 	}
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return 0;
+	}
+	ftp->in_use = true;
 	if (!ftp_type(ftp, type)) {
 		goto bail;
 	}
@@ -967,9 +972,11 @@ ftp_get(ftpbuf_t *ftp, php_stream *outstream, const char *path, const size_t pat
 		goto bail;
 	}
 
+	ftp->in_use = false;
 	return 1;
 bail:
 	data_close(ftp);
+	ftp->in_use = false;
 	return 0;
 }
 /* }}} */
@@ -1057,6 +1064,11 @@ ftp_put(ftpbuf_t *ftp, const char *path, const size_t path_len, php_stream *inst
 	if (ftp == NULL) {
 		return 0;
 	}
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return 0;
+	}
+	ftp->in_use = true;
 	if (!ftp_type(ftp, type)) {
 		goto bail;
 	}
@@ -1097,9 +1109,11 @@ ftp_put(ftpbuf_t *ftp, const char *path, const size_t path_len, php_stream *inst
 	if (!ftp_getresp(ftp) || (ftp->resp != 226 && ftp->resp != 250 && ftp->resp != 200)) {
 		goto bail;
 	}
+	ftp->in_use = false;
 	return 1;
 bail:
 	data_close(ftp);
+	ftp->in_use = false;
 	return 0;
 }
 /* }}} */
@@ -1114,6 +1128,11 @@ ftp_append(ftpbuf_t *ftp, const char *path, const size_t path_len, php_stream *i
 	if (ftp == NULL) {
 		return 0;
 	}
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return 0;
+	}
+	ftp->in_use = true;
 	if (!ftp_type(ftp, type)) {
 		goto bail;
 	}
@@ -1141,9 +1160,11 @@ ftp_append(ftpbuf_t *ftp, const char *path, const size_t path_len, php_stream *i
 	if (!ftp_getresp(ftp) || (ftp->resp != 226 && ftp->resp != 250 && ftp->resp != 200)) {
 		goto bail;
 	}
+	ftp->in_use = false;
 	return 1;
 bail:
 	data_close(ftp);
+	ftp->in_use = false;
 	return 0;
 }
 /* }}} */
@@ -2055,6 +2076,10 @@ ftp_genlist(ftpbuf_t *ftp, const char *cmd, const size_t cmd_len, const char *pa
 	char		**entry;
 	char		*text;
 
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return NULL;
+	}
 
 	if ((tmpstream = php_stream_fopen_tmpfile()) == NULL) {
 		php_error_docref(NULL, E_WARNING, "Unable to create temporary file.  Check permissions in temporary files directory.");
@@ -2156,6 +2181,11 @@ ftp_nb_get(ftpbuf_t *ftp, php_stream *outstream, const char *path, const size_t
 		return PHP_FTP_FAILED;
 	}
 
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return PHP_FTP_FAILED;
+	}
+
 	if (ftp->data != NULL) {
 		/* If there is a transfer in action, abort it.
 		 * If we don't, we get an invalid state and memory leaks when the new connection gets opened. */
@@ -2223,11 +2253,17 @@ ftp_nb_continue_read(ftpbuf_t *ftp)
 
 	data = ftp->data;
 
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return PHP_FTP_FAILED;
+	}
+
 	/* check if there is already more data */
 	if (!data_available(ftp, data->fd, false)) {
 		return PHP_FTP_MOREDATA;
 	}
 
+	ftp->in_use = true;
 	type = ftp->type;
 
 	lastch = ftp->lastch;
@@ -2251,6 +2287,7 @@ ftp_nb_continue_read(ftpbuf_t *ftp)
 		}
 
 		ftp->lastch = lastch;
+		ftp->in_use = false;
 		return PHP_FTP_MOREDATA;
 	}
 
@@ -2265,9 +2302,11 @@ ftp_nb_continue_read(ftpbuf_t *ftp)
 	}
 
 	ftp->nb = 0;
+	ftp->in_use = false;
 	return PHP_FTP_FINISHED;
 bail:
 	ftp->nb = 0;
+	ftp->in_use = false;
 	data_close(ftp);
 	return PHP_FTP_FAILED;
 }
@@ -2283,6 +2322,10 @@ ftp_nb_put(ftpbuf_t *ftp, const char *path, const size_t path_len, php_stream *i
 	if (ftp == NULL) {
 		return 0;
 	}
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return PHP_FTP_FAILED;
+	}
 	if (!ftp_type(ftp, type)) {
 		goto bail;
 	}
@@ -2330,16 +2373,24 @@ ftp_nb_put(ftpbuf_t *ftp, const char *path, const size_t path_len, php_stream *i
 int
 ftp_nb_continue_write(ftpbuf_t *ftp)
 {
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		return PHP_FTP_FAILED;
+	}
+
 	/* check if we can write more data */
 	if (!data_writeable(ftp, ftp->data->fd)) {
 		return PHP_FTP_MOREDATA;
 	}
 
+	ftp->in_use = true;
+
 	if (ftp_send_stream_to_data_socket(ftp, ftp->data, ftp->stream, ftp->type, true) != SUCCESS) {
 		goto bail;
 	}
 
 	if (!php_stream_eof(ftp->stream)) {
+		ftp->in_use = false;
 		return PHP_FTP_MOREDATA;
 	}
 
@@ -2349,10 +2400,12 @@ ftp_nb_continue_write(ftpbuf_t *ftp)
 		goto bail;
 	}
 	ftp->nb = 0;
+	ftp->in_use = false;
 	return PHP_FTP_FINISHED;
 bail:
 	data_close(ftp);
 	ftp->nb = 0;
+	ftp->in_use = false;
 	return PHP_FTP_FAILED;
 }
 /* }}} */
diff --git a/ext/ftp/ftp.h b/ext/ftp/ftp.h
index 94abc588ca85..91aafad02b79 100644
--- a/ext/ftp/ftp.h
+++ b/ext/ftp/ftp.h
@@ -73,6 +73,7 @@ typedef struct ftpbuf
 	databuf_t		*data;	/* Data connection for "nonblocking" transfers */
 	php_stream		*stream; /* output stream for "nonblocking" transfers */
 	bool			nb;		/* "nonblocking" transfer in progress */
+	bool			in_use;		/* engine transfer in progress; blocks re-entrant ftp_close */
 	char			lastch;		/* last char of previous call */
 	bool			direction;	/* recv = 0 / send = 1 */
 	bool			closestream;/* close or not close stream */
diff --git a/ext/ftp/php_ftp.c b/ext/ftp/php_ftp.c
index 8fa7675c6e9d..432270cff190 100644
--- a/ext/ftp/php_ftp.c
+++ b/ext/ftp/php_ftp.c
@@ -648,6 +648,11 @@ PHP_FUNCTION(ftp_nb_fget)
 	}
 
 	/* configuration */
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		RETURN_FALSE;
+	}
+
 	ftp->direction = 0;   /* recv */
 	ftp->closestream = 0; /* do not close */
 
@@ -761,6 +766,10 @@ PHP_FUNCTION(ftp_nb_get)
 		RETURN_THROWS();
 	}
 	GET_FTPBUF(ftp, z_ftp);
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		RETURN_FALSE;
+	}
 	XTYPE(xtype, mode);
 
 	/* ignore autoresume if autoseek is switched off */
@@ -798,8 +807,8 @@ PHP_FUNCTION(ftp_nb_get)
 	ftp->closestream = 1; /* do close */
 
 	if ((ret = ftp_nb_get(ftp, outstream, remote, remote_len, xtype, resumepos)) == PHP_FTP_FAILED) {
-		php_stream_close(outstream);
 		ftp->stream = NULL;
+		php_stream_close(outstream);
 		VCWD_UNLINK(local);
 		if (*ftp->inbuf) {
 			php_error_docref(NULL, E_WARNING, "%s", ftp->inbuf);
@@ -808,8 +817,8 @@ PHP_FUNCTION(ftp_nb_get)
 	}
 
 	if (ret == PHP_FTP_FINISHED){
-		php_stream_close(outstream);
 		ftp->stream = NULL;
+		php_stream_close(outstream);
 	}
 
 	RETURN_LONG(ret);
@@ -937,6 +946,11 @@ PHP_FUNCTION(ftp_nb_fput)
 	}
 
 	/* configuration */
+	if (ftp->in_use) {
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		RETURN_FALSE;
+	}
+
 	ftp->direction = 1;   /* send */
 	ftp->closestream = 0; /* do not close */
 
@@ -1077,6 +1091,12 @@ PHP_FUNCTION(ftp_nb_put)
 		}
 	}
 
+	if (ftp->in_use) {
+		php_stream_close(instream);
+		php_error_docref(NULL, E_WARNING, "FTP\\Connection is already in use");
+		RETURN_FALSE;
+	}
+
 	/* configuration */
 	ftp->direction = 1;   /* send */
 	ftp->closestream = 1; /* do close */
@@ -1084,8 +1104,8 @@ PHP_FUNCTION(ftp_nb_put)
 	ret = ftp_nb_put(ftp, remote, remote_len, instream, xtype, startpos);
 
 	if (ret != PHP_FTP_MOREDATA) {
-		php_stream_close(instream);
 		ftp->stream = NULL;
+		php_stream_close(instream);
 	}
 
 	if (ret == PHP_FTP_FAILED) {
@@ -1220,6 +1240,10 @@ PHP_FUNCTION(ftp_close)
 
 	obj = ftp_object_from_zend_object(Z_OBJ_P(z_ftp));
 	if (obj->ftp) {
+		if (obj->ftp->in_use) {
+			zend_throw_error(NULL, "Cannot close FTP\\Connection while a transfer is in progress");
+			RETURN_THROWS();
+		}
 		success = ftp_quit(obj->ftp);
 		ftp_close(obj->ftp);
 		obj->ftp = NULL;
diff --git a/ext/ftp/tests/ftp_close_during_transfer.phpt b/ext/ftp/tests/ftp_close_during_transfer.phpt
new file mode 100644
index 000000000000..72e410603921
--- /dev/null
+++ b/ext/ftp/tests/ftp_close_during_transfer.phpt
@@ -0,0 +1,44 @@
+--TEST--
+ftp_close() from a stream wrapper during a transfer throws instead of freeing the connection
+--EXTENSIONS--
+ftp
+pcntl
+--FILE--
+<?php
+require 'server.inc';
+
+class CloseDuringWrite {
+    public $context;
+    public static $ftp;
+    public function stream_open($path, $mode, $options, &$opened_path) {
+        return true;
+    }
+    public function stream_write($data) {
+        ftp_close(self::$ftp);
+        return strlen($data);
+    }
+    public function stream_close() {}
+    public function stream_eof() {
+        return true;
+    }
+}
+
+stream_wrapper_register('reentrant', CloseDuringWrite::class);
+
+$ftp = ftp_connect('127.0.0.1', $port);
+var_dump(ftp_login($ftp, 'user', 'pass'));
+CloseDuringWrite::$ftp = $ftp;
+
+try {
+    @ftp_get($ftp, 'reentrant://sink', 'a story.txt', FTP_BINARY);
+} catch (\Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+ftp_close($ftp);
+echo "closed\n";
+?>
+--EXPECT--
+bool(true)
+Cannot close FTP\Connection while a transfer is in progress
+closed
diff --git a/ext/ftp/tests/ftp_nb_close_during_transfer.phpt b/ext/ftp/tests/ftp_nb_close_during_transfer.phpt
new file mode 100644
index 000000000000..702648f69592
--- /dev/null
+++ b/ext/ftp/tests/ftp_nb_close_during_transfer.phpt
@@ -0,0 +1,44 @@
+--TEST--
+ftp_close() from a stream wrapper during a non-blocking transfer throws instead of freeing the connection
+--EXTENSIONS--
+ftp
+pcntl
+--FILE--
+<?php
+require 'server.inc';
+
+class CloseDuringNbWrite {
+    public $context;
+    public static $ftp;
+    public function stream_open($path, $mode, $options, &$opened_path) {
+        return true;
+    }
+    public function stream_write($data) {
+        ftp_close(self::$ftp);
+        return strlen($data);
+    }
+    public function stream_close() {}
+    public function stream_eof() {
+        return true;
+    }
+}
+
+stream_wrapper_register('reentrantnb', CloseDuringNbWrite::class);
+
+$ftp = ftp_connect('127.0.0.1', $port);
+var_dump(ftp_login($ftp, 'user', 'pass'));
+CloseDuringNbWrite::$ftp = $ftp;
+
+try {
+    @ftp_nb_get($ftp, 'reentrantnb://sink', 'a story.txt', FTP_BINARY);
+} catch (\Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+ftp_close($ftp);
+echo "closed\n";
+?>
+--EXPECT--
+bool(true)
+Cannot close FTP\Connection while a transfer is in progress
+closed
diff --git a/ext/ftp/tests/ftp_nb_get_during_nb_transfer.phpt b/ext/ftp/tests/ftp_nb_get_during_nb_transfer.phpt
new file mode 100644
index 000000000000..deb1698c77c5
--- /dev/null
+++ b/ext/ftp/tests/ftp_nb_get_during_nb_transfer.phpt
@@ -0,0 +1,44 @@
+--TEST--
+Re-entrant ftp_nb_get() from a stream wrapper during an active non-blocking ftp_nb_get() must not corrupt the outer transfer
+--EXTENSIONS--
+ftp
+pcntl
+--FILE--
+<?php
+require 'server.inc';
+
+class NbGetDuringNbGet {
+    public $context;
+    public static $ftp;
+    public function stream_open($path, $mode, $options, &$opened_path) {
+        return true;
+    }
+    public function stream_write($data) {
+        @ftp_nb_get(self::$ftp, 'php://memory', 'a story.txt', FTP_BINARY);
+        return strlen($data);
+    }
+    public function stream_close() {}
+    public function stream_eof() {
+        return true;
+    }
+}
+
+stream_wrapper_register('reentrantnbget', NbGetDuringNbGet::class);
+
+$ftp = ftp_connect('127.0.0.1', $port);
+var_dump(ftp_login($ftp, 'user', 'pass'));
+NbGetDuringNbGet::$ftp = $ftp;
+
+$r = @ftp_nb_get($ftp, 'reentrantnbget://sink', 'a story.txt', FTP_BINARY);
+while ($r == FTP_MOREDATA) {
+    $r = @ftp_nb_continue($ftp);
+}
+var_dump($r === FTP_FINISHED);
+
+ftp_close($ftp);
+echo "closed\n";
+?>
+--EXPECT--
+bool(true)
+bool(true)
+closed
diff --git a/ext/ftp/tests/ftp_nb_get_during_transfer.phpt b/ext/ftp/tests/ftp_nb_get_during_transfer.phpt
new file mode 100644
index 000000000000..c7920496feb4
--- /dev/null
+++ b/ext/ftp/tests/ftp_nb_get_during_transfer.phpt
@@ -0,0 +1,40 @@
+--TEST--
+Re-entrant ftp_nb_get() from a stream wrapper during a blocking ftp_get() must not free the active data connection
+--EXTENSIONS--
+ftp
+pcntl
+--FILE--
+<?php
+require 'server.inc';
+
+class NbGetDuringGet {
+    public $context;
+    public static $ftp;
+    public function stream_open($path, $mode, $options, &$opened_path) {
+        return true;
+    }
+    public function stream_write($data) {
+        @ftp_nb_get(self::$ftp, 'php://memory', 'a story.txt', FTP_BINARY);
+        return strlen($data);
+    }
+    public function stream_close() {}
+    public function stream_eof() {
+        return true;
+    }
+}
+
+stream_wrapper_register('reentrantget', NbGetDuringGet::class);
+
+$ftp = ftp_connect('127.0.0.1', $port);
+var_dump(ftp_login($ftp, 'user', 'pass'));
+NbGetDuringGet::$ftp = $ftp;
+
+var_dump(@ftp_get($ftp, 'reentrantget://sink', 'a story.txt', FTP_BINARY));
+
+ftp_close($ftp);
+echo "closed\n";
+?>
+--EXPECT--
+bool(true)
+bool(true)
+closed