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Subject: Re: [PATCH] usb: core: safely deal with the dynamic quirk lists
From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
In-Reply-To: <20180914085816.10888-1-harry.pan@intel.com>
Date:   Mon, 17 Sep 2018 15:05:51 +0800
Cc:     LKML <linux-kernel@vger.kernel.org>, gs0622@gmail.com,
        jongpil19.jung@samsung.com, rajatja@chromium.org,
        Greg KH <gregkh@linuxfoundation.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        snecknico@gmail.com, jackstocker.93@gmail.com, oneukum@suse.com,
        linux-usb@vger.kernel.org
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Message-Id: <8950C3C8-AF9B-49DF-BE29-5F6892FCCEC8@canonical.com>
References: <20180914085816.10888-1-harry.pan@intel.com>
To:     Harry Pan <harry.pan@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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at 16:58, Harry Pan <harry.pan@intel.com> wrote:

> Applying dynamic usbcore quirks in early booting when the slab is
> not yet ready would cause kernel panic of null pointer dereference
> because the quirk_count has been counted as 1 while the quirk_list
> was failed to allocate.
>
> i.e.,
> [    1.044970] BUG: unable to handle kernel NULL pointer dereference  
> at           (null)
> [    1.044995] IP: [<ffffffffb0953ec7>] usb_detect_quirks+0x88/0xd1
> [    1.045016] PGD 0
> [    1.045026] Oops: 0000 [#1] PREEMPT SMP
> [    1.046986] gsmi: Log Shutdown Reason 0x03
> [    1.046995] Modules linked in:
> [    1.047008] CPU: 0 PID: 81 Comm: kworker/0:3 Not tainted 4.4.154 #28
> [    1.047016] Hardware name: Google Coral/Coral, BIOS  
> Google_Coral.10068.27.0 12/04/2017
> [    1.047028] Workqueue: usb_hub_wq hub_event
> [    1.047037] task: ffff88017a321c80 task.stack: ffff88017a384000
> [    1.047044] RIP: 0010:[<ffffffffb0953ec7>]  [<ffffffffb0953ec7>]  
> usb_detect_quirks+0x88/0xd1
>
> To tackle this odd, let's balance the quirk_count to 0 when the kcalloc
> call fails, and defer the quirk setting into a lower level callback
> which ensures that the kernel memory management has been initialized.
>
> Fixes: 027bd6cafd9a ("usb: core: Add "quirks" parameter for usbcore")
>
> Signed-off-by: Harry Pan <harry.pan@intel.com>

Thanks for the catch!

This issue doesn't appear when usbcore is built as module.

Acked-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

> ---
>  drivers/usb/core/quirks.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
> index 097057d2eacf..1fe9843fb9c8 100644
> --- a/drivers/usb/core/quirks.c
> +++ b/drivers/usb/core/quirks.c
> @@ -58,6 +58,7 @@ static int quirks_param_set(const char *val, const  
> struct kernel_param *kp)
>  	quirk_list = kcalloc(quirk_count, sizeof(struct quirk_entry),
>  			     GFP_KERNEL);
>  	if (!quirk_list) {
> +		quirk_count = 0;
>  		mutex_unlock(&quirk_mutex);
>  		return -ENOMEM;
>  	}
> @@ -154,7 +155,7 @@ static struct kparam_string quirks_param_string = {
>  	.string = quirks_param,
>  };
>
> -module_param_cb(quirks, &quirks_param_ops, &quirks_param_string, 0644);
> +device_param_cb(quirks, &quirks_param_ops, &quirks_param_string, 0644);
>  MODULE_PARM_DESC(quirks, "Add/modify USB quirks by specifying quirks=vendorID:productID:quirks");
>
>  /* Lists of quirky USB devices, split in device quirks and interface quirks.
> -- 
> 2.16.4