linux-kernel - [PATCH v2] usb: gadget: u_serial: Disable ep before setting port to null to fix the crash caused by port being null

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Message-ID:
 <TYUPR06MB6217DAA095A9863D4B58D57CD23B2@TYUPR06MB6217.apcprd06.prod.outlook.com>
Date: Mon, 16 Dec 2024 12:31:45 +0000
From: 胡连勤 <hulianqin@...o.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, Prashanth K
	<quic_prashk@...cinc.com>, "mwalle@...nel.org" <mwalle@...nel.org>,
	"quic_jjohnson@...cinc.com" <quic_jjohnson@...cinc.com>,
	"dbrownell@...rs.sourceforge.net" <dbrownell@...rs.sourceforge.net>
CC: "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	胡连勤 <hulianqin@...o.com>, opensource.kernel
	<opensource.kernel@...o.com>
Subject: [PATCH v2] usb: gadget: u_serial: Disable ep before setting port to
 null to fix the crash caused by port being null

From: Lianqin Hu <hulianqin@...o.com>

Considering that in some extreme cases, when performing the
unbinding operation, gserial_disconnect has cleared gser->ioport,
which triggers gadget reconfiguration, and then calls gs_read_complete,
resulting in access to a null pointer. Therefore, ep is disabled before
gserial_disconnect sets port to null to prevent this from happening.

Call trace:
 gs_read_complete+0x58/0x240
 usb_gadget_giveback_request+0x40/0x160
 dwc3_remove_requests+0x170/0x484
 dwc3_ep0_out_start+0xb0/0x1d4
 __dwc3_gadget_start+0x25c/0x720
 kretprobe_trampoline.cfi_jt+0x0/0x8
 kretprobe_trampoline.cfi_jt+0x0/0x8
 udc_bind_to_driver+0x1d8/0x300
 usb_gadget_probe_driver+0xa8/0x1dc
 gadget_dev_desc_UDC_store+0x13c/0x188
 configfs_write_iter+0x160/0x1f4
 vfs_write+0x2d0/0x40c
 ksys_write+0x7c/0xf0
 __arm64_sys_write+0x20/0x30
 invoke_syscall+0x60/0x150
 el0_svc_common+0x8c/0xf8
 do_el0_svc+0x28/0xa0
 el0_svc+0x24/0x84

Fixes: c1dca562be8a ("usb gadget: split out serial core")
Cc: stable@...r.kernel.org

Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Lianqin Hu <hulianqin@...o.com>

v2:
 - Remove some address information from patch descriptions
 - Link to v1: https://lore.kernel.org/all/TYUPR06MB621763AB815989161F4033AFD2762@TYUPR06MB6217.apcprd06.prod.outlook.com/
 - Link to suggestions: https://lore.kernel.org/all/TYUPR06MB6217DE28012FFEC5E808DD64D2962@TYUPR06MB6217.apcprd06.prod.outlook.com/

 drivers/usb/gadget/function/u_serial.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 53d9fc41acc5..bc143a86c2dd 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1420,6 +1420,10 @@ void gserial_disconnect(struct gserial *gser)
 	/* REVISIT as above: how best to track this? */
 	port->port_line_coding = gser->port_line_coding;
 
+	/* disable endpoints, aborting down any active I/O */
+	usb_ep_disable(gser->out);
+	usb_ep_disable(gser->in);
+
 	port->port_usb = NULL;
 	gser->ioport = NULL;
 	if (port->port.count > 0) {
@@ -1431,10 +1435,6 @@ void gserial_disconnect(struct gserial *gser)
 	spin_unlock(&port->port_lock);
 	spin_unlock_irqrestore(&serial_port_lock, flags);
 
-	/* disable endpoints, aborting down any active I/O */
-	usb_ep_disable(gser->out);
-	usb_ep_disable(gser->in);
-
 	/* finally, free any unused/unusable I/O buffers */
 	spin_lock_irqsave(&port->port_lock, flags);
 	if (port->port.count == 0)
-- 
2.39.0