linux-kernel - Re: [PATCH] fbdev: pxafb: Fix use after free vulnerability in pxafb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <1C2E4AB314A69BCF+750f4f16.c216.191e7118e58.Coremail.kxwang23@m.fudan.edu.cn>
Date: Fri, 13 Sep 2024 00:29:33 +0800 (CST)
From: "Kaixin Wang" <kxwang23@...udan.edu.cn>
To: "Helge Deller" <deller@....de>
Cc: 21210240012@...udan.edu.cn, 21302010073@...udan.edu.cn, 
	linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, kuninori.morimoto.gx@...esas.com, 
	laurent.pinchart@...asonboard.com
Subject: Re: [PATCH] fbdev: pxafb: Fix use after free vulnerability in
 pxafb_driver Driver Due to Race Condition



At 2024-09-12 01:38:26, "Helge Deller" <deller@....de> wrote:
>On 9/11/24 16:29, Kaixin Wang wrote:
>> In the pxafb_probe function, it calls the pxafb_init_fbinfo function,
>> after which &fbi->task is associated with pxafb_task. Moreover,
>> within this pxafb_init_fbinfo function, the pxafb_blank function
>> within the &pxafb_ops struct is capable of scheduling work.
>>
>> If we remove the module which will call pxafb_remove to make cleanup,
>> it will call unregister_framebuffer function which can call
>> do_unregister_framebuffer to free fbi->fb through
>> put_fb_info(fb_info), while the work mentioned above will be used.
>> The sequence of operations that may lead to a UAF bug is as follows:
>>
>> CPU0                                                CPU1
>>
>>                                     | pxafb_task
>> pxafb_remove                       |
>> unregister_framebuffer(info)       |
>> do_unregister_framebuffer(fb_info) |
>> put_fb_info(fb_info)               |
>> // free fbi->fb                    | set_ctrlr_state(fbi, state)
>>                                     | __pxafb_lcd_power(fbi, 0)
>>                                     | fbi->lcd_power(on, &fbi->fb.var)
>>                                     | //use fbi->fb
>>
>> Fix it by ensuring that the work is canceled before proceeding
>> with the cleanup in pxafb_remove.
>>
>> Note that only root user can remove the driver at runtime.
>>
>> Signed-off-by: Kaixin Wang <kxwang23@...udan.edu.cn>
>> ---
>>   drivers/video/fbdev/pxafb.c | 1 +
>>   1 file changed, 1 insertion(+)
>
>I've added the patch to the fbdev git tree, but changed the title to:
>"fbdev: pxafb: Fix possible use after free in pxafb_task()"
>
>Thanks!
>Helge
>
>


Thanks for the review! I appreciate the adjustment to the patch title to make it more precise.

Best regards,
Kaixin Wang