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Message-ID: <CAOf5uw=-giw8DSY3cX_No73THAwbKc+5Pgy8Vap-AeeF5h+VrA@mail.gmail.com>
Date: Tue, 27 Aug 2024 19:18:51 +0200
From: Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To: 胡连勤 <hulianqin@...o.com>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, Prashanth K <quic_prashk@...cinc.com>,
"quic_jjohnson@...cinc.com" <quic_jjohnson@...cinc.com>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"opensource.kernel" <opensource.kernel@...o.com>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v8] usb: gadget: u_serial: Add null pointer check in
gs_read_complete & gs_write_complete
Hi 胡连勤
On Tue, Aug 27, 2024 at 12:19 PM 胡连勤 <hulianqin@...o.com> wrote:
>
> From: Lianqin Hu <hulianqin@...o.com>
>
> Considering that in some extreme cases, when the unbind operation
> is being executed, gserial_disconnect has already cleared gser->ioport,
> and gs_read_complete gets called afterwards, which results in accessing
> null pointer, add a null pointer check to prevent this situation.
>
Was better not to get rid of the test case. What config.usb in android does is
trigger a gadget reconfiguration on this property change. It means that I expect
the android test, try to change gadget and moving from one type to
another in a loop.
Is that correct? If so will be nice that you describe
> 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@...r.kernel.org
> Suggested-by: Prashanth K <quic_prashk@...cinc.com>
> Signed-off-by: Lianqin Hu <hulianqin@...o.com>
> ---
> 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,
> --
I can base my review on what was done before for suspend/resume and
this implementation looks the same.
I don't think that both are optimal but this should avoid race on completion.
Michael
> 2.39.0
>
--
Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
M. +39 347 913 2170
michael@...rulasolutions.com
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