linux-kernel - Re: [PATCH v3] 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: <b511a84b-62d9-43cf-9a16-f365832873cb@quicinc.com>
Date: Tue, 24 Dec 2024 10:23:09 +0530
From: Prashanth K <quic_prashk@...cinc.com>
To: 胡连勤 <hulianqin@...o.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "mwalle@...nel.org" <mwalle@...nel.org>,
        "quic_jjohnson@...cinc.com"
	<quic_jjohnson@...cinc.com>,
        David Brownell <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>,
        opensource.kernel <opensource.kernel@...o.com>
Subject: Re: [PATCH v3] usb: gadget: u_serial: Disable ep before setting port
 to null to fix the crash caused by port being null



On 17-12-24 01:28 pm, 胡连勤 wrote:
> 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.

gs_read_complete() gets port from ep->driver_data, and it shouldn't get
affected if gser->ioport is null as long as port[port_num].port is
valid. Am I missing something here?
> 
> 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
>
Regards,
Prashanth K