linux-kernel - Re: [syzbot] KASAN: use-after-free Read in dev

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Message-ID: <81102f38-3e1f-ec36-3119-a098bd5a85c4@gmail.com>
Date:   Wed, 23 Feb 2022 14:23:47 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     "Zhang, Qiang1" <qiang1.zhang@...el.com>,
        syzbot <syzbot+348b571beb5eeb70a582@...kaller.appspotmail.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>
Subject: Re: [syzbot] KASAN: use-after-free Read in dev_uevent

Hi Qiang1,

On 2/23/22 14:17, Zhang, Qiang1 wrote:
> 
> Cc: Alan Stern
>         Felipe Balbi
> 
> Hello syzbot, Please try it:
> 
>  From 574d45ff924e2d2f9b9f5cc3e846f8004498a811 Mon Sep 17 00:00:00 2001
> From: Zqiang <qiang1.zhang@...el.com>
> Date: Wed, 23 Feb 2022 18:18:22 +0800
> Subject: [PATCH] driver core: Fix use-after-free in dev_uevent()
> 
> In dev_uevent(), if the "dev->driver" is valid, the "dev->driver->name"
> be accessed, there may be a window period between these two operations.
> in this window period if the "dev->driver" is set to null
> (in usb_gadget_unregister_driver function), when the "dev->driver->name"
> is accessed again, invalid address will be accessed. fix it by checking
> "dev->driver" again.
> 
> Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> ---
>   drivers/base/core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 3d6430eb0c6a..a45b927ee76e 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2317,7 +2317,7 @@ static int dev_uevent(struct kobject *kobj, struct kobj_uevent_env *env)
>                  add_uevent_var(env, "DEVTYPE=%s", dev->type->name);
> 
>          if (dev->driver)
> -               add_uevent_var(env, "DRIVER=%s", dev->driver->name);
> +               add_uevent_var(env, "DRIVER=%s", dev_driver_string(dev));
> 
>          /* Add common DT information about the device */
>          of_device_uevent(dev, env);
> --
> 2.25.1
> 

you should use '#syz test' command to ask syzbot to test the patch. 
Basic syntax is '#syz test: <git tree> <branch or sha>' and syzbot will 
apply attached patch (if you have attached it)


More about syzbot interactions here [1].

[1] 
https://github.com/google/syzkaller/blob/15439f1624735bde5ae3f3b66c1b964a98




With regards,
Pavel Skripkin