Ping......
>From: Lianqin Hu <hulianqin@xxxxxxxx>
>
>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@xxxxxxxxxxxxxxx
>Suggested-by: Michael Nazzareno Trimarchi <michael@xxxxxxxxxxxxxxxxxxxx>
>Suggested-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
>Signed-off-by: Lianqin Hu <hulianqin@xxxxxxxx>
>---
>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
