linux-kernel - 答复: [PATCH v1] usb: gadget: u_serial: check Null pointer in EP callback

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Message-ID:
 <PUZPR06MB622403392E76A64749D068F6D28D2@PUZPR06MB6224.apcprd06.prod.outlook.com>
Date: Tue, 20 Aug 2024 09:13:36 +0000
From: 胡连勤 <hulianqin@...o.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC: "quic_prashk@...cinc.com" <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>, Michael Nazzareno Trimarchi
	<michael@...rulasolutions.com>
Subject:
 答复: [PATCH v1] usb: gadget: u_serial: check Null pointer in EP callback

Hello linux community expert:

>> Added null pointer check to avoid system crash.
>> 
>> 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
>> 
>> Signed-off-by: Lianqin Hu <hulianqin@...o.com>
>> ---
>> v1:
>   - Optimize code comments, delete log printing

>Also, same comment as before, what:
>  - causes port to be NULL
   When unbind, the gser_unbind function call gserial_disconnect to set gser->ioport = NULL, and struct gs_port *port = gser->ioport, resulting in port being NULL.
   It seems that there is a potential competition between the gs_read_complete function and the gserial_disconnect function.
>  - prevents it from changing to NULL right after you check it
   I've seen other functions, such as gserial_suspend and gserial_resume, which all perform port empty detection operations.

>Both need to be answered before we can take this change.

Thanks