[PATCH v9] usb: gadget: u_serial: Add null pointer check in gs_read_complete & gs_write_complete

胡连勤
2024-08-29T11:54:45Z

From: Lianqin Hu <hulianqin@vivo.com>

Considering that in some extreme cases, when the unbind operation
is being executed, gserial_disconnect has already cleared gser->ioport,
triggering a gadget reconfiguration at this time and gs_read_complete
gets called afterwards, which results in accessing null pointer,
add a null pointer check to prevent this situation.

Added a static spinlock to prevent gser->ioport from becoming
null after the newly added check.

Unable to handle kernel NULL pointer dereference at
virtual address 00000000000001a8
pc : gs_read_complete+0x58/0x240
lr : usb_gadget_giveback_request+0x40/0x160
sp : ffffffc00f1539c0
x29: ffffffc00f1539c0 x28: ffffff8002a30000 x27: 0000000000000000
x26: ffffff8002a30000 x25: 0000000000000000 x24: ffffff8002a30000
x23: ffffff8002ff9a70 x22: ffffff898e7a7b00 x21: ffffff803c9af9d8
x20: ffffff898e7a7b00 x19: 00000000000001a8 x18: ffffffc0099fd098
x17: 0000000000001000 x16: 0000000080000000 x15: 0000000ac1200000
x14: 0000000000000003 x13: 000000000000d5e8 x12: 0000000355c314ac
x11: 0000000000000015 x10: 0000000000000012 x9 : 0000000000000008
x8 : 0000000000000000 x7 : 0000000000000000 x6 : ffffff887cd12000
x5 : 0000000000000002 x4 : ffffffc00f9b07f0 x3 : ffffffc00f1538d0
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 00000000000001a8
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
el0t_64_sync_handler+0x88/0xec
el0t_64_sync+0x1b4/0x1b8
Code: aa1f03e1 aa1303e0 52800022 2a0103e8 (88e87e62)
---[ end trace 938847327a739172 ]---
Kernel panic - not syncing: Oops: Fatal exception

Fixes: c1dca562be8a ("usb gadget: split out serial core")
Cc: stable@vger.kernel.org
Suggested-by: Michael Nazzareno Trimarchi <michael@amarulasolutions.com>
Suggested-by: Prashanth K <quic_prashk@quicinc.com>
Signed-off-by: Lianqin Hu <hulianqin@vivo.com>
---
v9: Add gadget reconfiguration description in commit message.
v8: Updated patch submission description as suggested in v7 discussion.
v7: Remove code comments.
v6: Update the commit text.
v5: Add the Fixes tag.
v4: CC stable kernel.
v3: Add serial_port_lock protection when checking port pointer.
v2: Optimize code comments.
v1: Delete log printing.

drivers/usb/gadget/function/u_serial.c | 31 +++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index b394105e55d6..66d918523b3e 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -452,20 +452,41 @@ static void gs_rx_push(struct work_struct *work)

static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
{
- struct gs_port *port = ep->driver_data;
+ struct gs_port *port;
+ unsigned long flags;
+
+ spin_lock_irqsave(&serial_port_lock, flags);
+ port = ep->driver_data;
+
+ if (!port) {
+ spin_unlock_irqrestore(&serial_port_lock, flags);
+ return;
+ }

- /* Queue all received data until the tty layer is ready for it. */
spin_lock(&port->port_lock);
+ spin_unlock(&serial_port_lock);
+
+ /* Queue all received data until the tty layer is ready for it. */
list_add_tail(&req->list, &port->read_queue);
schedule_delayed_work(&port->push, 0);
- spin_unlock(&port->port_lock);
+ spin_unlock_irqrestore(&port->port_lock, flags);
}

static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
{
- struct gs_port *port = ep->driver_data;
+ struct gs_port *port;
+ unsigned long flags;
+
+ spin_lock_irqsave(&serial_port_lock, flags);
+ port = ep->driver_data;
+
+ if (!port) {
+ spin_unlock_irqrestore(&serial_port_lock, flags);
+ return;
+ }

spin_lock(&port->port_lock);
+ spin_unlock(&serial_port_lock);
list_add(&req->list, &port->write_pool);
port->write_started--;

@@ -486,7 +507,7 @@ static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
break;
}

- spin_unlock(&port->port_lock);
+ spin_unlock_irqrestore(&port->port_lock, flags);
}

static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
--
2.39.0