diff mbox series

[v3] Bluetooth: btmtk: Fix null pointer when processing coredump

Message ID 20230712051857.13812-1-chris.lu@mediatek.com (mailing list archive)
State New, archived
Headers show
Series [v3] Bluetooth: btmtk: Fix null pointer when processing coredump | expand

Commit Message

Chris Lu July 12, 2023, 5:18 a.m. UTC 
There may be a potential null pointer risk if offset value is
less than 0 when doing memcmp in btmtk_process_coredump().
Checking offset is valid before doing memcmp.

Signed-off-by: Chris Lu <chris.lu@mediatek.com>
Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
---
v2: fix typo
v3: fix bot checking error
---
 drivers/bluetooth/btmtk.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Comments

Paul Menzel July 12, 2023, 6:11 a.m. UTC | #1 
Dear Chris,


Am 12.07.23 um 07:18 schrieb Chris Lu:
> There may be a potential null pointer risk if offset value is
> less than 0 when doing memcmp in btmtk_process_coredump().
> Checking offset is valid before doing memcmp.

Use imperative mood: Check offset …

> Signed-off-by: Chris Lu <chris.lu@mediatek.com>
> Co-developed-by: Sean Wang <sean.wang@mediatek.com>
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> ---
> v2: fix typo
> v3: fix bot checking error
> ---
>   drivers/bluetooth/btmtk.c | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
> index 786f775196ae..0f290430ae0e 100644
> --- a/drivers/bluetooth/btmtk.c
> +++ b/drivers/bluetooth/btmtk.c
> @@ -370,7 +370,7 @@ EXPORT_SYMBOL_GPL(btmtk_register_coredump);
>   int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff *skb)
>   {
>   	struct btmediatek_data *data = hci_get_priv(hdev);
> -	int err;
> +	int err, offset;
>   
>   	if (!IS_ENABLED(CONFIG_DEV_COREDUMP))
>   		return 0;
> @@ -392,15 +392,15 @@ int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff *skb)
>   		if (err < 0)
>   			break;
>   		data->cd_info.cnt++;
> +		offset = skb->len - sizeof(MTK_COREDUMP_END);

For `sizeof()` shouldn’t you use `size_t`? But that is unsigned of 
course. Maybe ssize_t then?

>   
>   		/* Mediatek coredump data would be more than MTK_COREDUMP_NUM */
> -		if (data->cd_info.cnt > MTK_COREDUMP_NUM &&
> -		    skb->len > sizeof(MTK_COREDUMP_END) &&
> -		    !memcmp((char *)&skb->data[skb->len - sizeof(MTK_COREDUMP_END)],
> -			    MTK_COREDUMP_END, sizeof(MTK_COREDUMP_END) - 1)) {
> -			bt_dev_info(hdev, "Mediatek coredump end");
> -			hci_devcd_complete(hdev);
> -		}
> +		if (data->cd_info.cnt > MTK_COREDUMP_NUM && offset > 0)

Why not keep it like before, and just add the condition `skb->len < 
sizeof(MTK_COREDUMP_END)`? The compiler is probably going to optimize so 
the value is not calculated twice.


Kind regards,

Paul


> +			if (!memcmp((char *)&skb->data[offset], MTK_COREDUMP_END,
> +				    sizeof(MTK_COREDUMP_END) - 1)) {
> +				bt_dev_info(hdev, "Mediatek coredump end");
> +				hci_devcd_complete(hdev);
> +			}
>   
>   		break;
>   	}
Chris Lu July 12, 2023, 8:53 a.m. UTC | #2 
On Wed, 2023-07-12 at 08:11 +0200, Paul Menzel wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  Dear Chris,
> 
Dear Paul,

Thanks for your review and feedback to Mediatek's Bluetooth driver
code.

> 
> Am 12.07.23 um 07:18 schrieb Chris Lu:
> > There may be a potential null pointer risk if offset value is
> > less than 0 when doing memcmp in btmtk_process_coredump().
> > Checking offset is valid before doing memcmp.
> 
> Use imperative mood: Check offset …
> 
> > Signed-off-by: Chris Lu <chris.lu@mediatek.com>
> > Co-developed-by: Sean Wang <sean.wang@mediatek.com>
> > Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> > ---
> > v2: fix typo
> > v3: fix bot checking error
> > ---
> >   drivers/bluetooth/btmtk.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
> > index 786f775196ae..0f290430ae0e 100644
> > --- a/drivers/bluetooth/btmtk.c
> > +++ b/drivers/bluetooth/btmtk.c
> > @@ -370,7 +370,7 @@ EXPORT_SYMBOL_GPL(btmtk_register_coredump);
> >   int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff
> *skb)
> >   {
> >   struct btmediatek_data *data = hci_get_priv(hdev);
> > -int err;
> > +int err, offset;
> >   
> >   if (!IS_ENABLED(CONFIG_DEV_COREDUMP))
> >   return 0;
> > @@ -392,15 +392,15 @@ int btmtk_process_coredump(struct hci_dev
> *hdev, struct sk_buff *skb)
> >   if (err < 0)
> >   break;
> >   data->cd_info.cnt++;
> > +offset = skb->len - sizeof(MTK_COREDUMP_END);
> 
> For `sizeof()` shouldn’t you use `size_t`? But that is unsigned of 
> course. Maybe ssize_t then?
> 
yes, it's better to use ssize_t or size_t, I'll change declaratins of
offset from int to ssize_t.

> >   
> >   /* Mediatek coredump data would be more than MTK_COREDUMP_NUM */
> > -if (data->cd_info.cnt > MTK_COREDUMP_NUM &&
> > -    skb->len > sizeof(MTK_COREDUMP_END) &&
> > -    !memcmp((char *)&skb->data[skb->len -
> sizeof(MTK_COREDUMP_END)],
> > -    MTK_COREDUMP_END, sizeof(MTK_COREDUMP_END) - 1)) {
> > -bt_dev_info(hdev, "Mediatek coredump end");
> > -hci_devcd_complete(hdev);
> > -}
> > +if (data->cd_info.cnt > MTK_COREDUMP_NUM && offset > 0)
> 
> Why not keep it like before, and just add the condition `skb->len < 
> sizeof(MTK_COREDUMP_END)`? The compiler is probably going to optimize
> so 
> the value is not calculated twice.
> 
> 
> Kind regards,
> 
> Paul
> 
> 
The reason why I send this patch is when I backport devcoredump feature
to specific project with older kernel version, the compiler might not
so optimized that it would cause kernel panic when run into memcmp.
As a result, make sure `skb->len > sizeof(MTK_COREDUMP_END) ` before
doing memcmp part can avoid null pointer issue.
Besides, only in condition 'data->cd_info.cnt > MTK_COREDUMP_NUM &&
offset > 0' need to do memcmp to check the end of coredump. Driver do
noting with condition `skb->len < sizeof(MTK_COREDUMP_END) ` that
additional condiction is not really necessary.

> > +if (!memcmp((char *)&skb->data[offset], MTK_COREDUMP_END,
> > +    sizeof(MTK_COREDUMP_END) - 1)) {
> > +bt_dev_info(hdev, "Mediatek coredump end");
> > +hci_devcd_complete(hdev);
> > +}
> >   
> >   break;
> >   }
Paul Menzel July 12, 2023, 9:25 a.m. UTC | #3 
Dear Chris,


Am 12.07.23 um 10:53 schrieb Chris Lu (陸稚泓):
> On Wed, 2023-07-12 at 08:11 +0200, Paul Menzel wrote:
>>   	
>> External email : Please do not click links or open attachments until
>> you have verified the sender or the content.

(It’d be nice if you removed such (automatically added) phrases from 
your reply.)

> Thanks for your review and feedback to Mediatek's Bluetooth driver
> code.

Thank you for your reply.

>> Am 12.07.23 um 07:18 schrieb Chris Lu:
>>> There may be a potential null pointer risk if offset value is
>>> less than 0 when doing memcmp in btmtk_process_coredump().
>>> Checking offset is valid before doing memcmp.
>>
>> Use imperative mood: Check offset …
>>
>>> Signed-off-by: Chris Lu <chris.lu@mediatek.com>
>>> Co-developed-by: Sean Wang <sean.wang@mediatek.com>
>>> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
>>> ---
>>> v2: fix typo
>>> v3: fix bot checking error
>>> ---
>>>    drivers/bluetooth/btmtk.c | 16 ++++++++--------
>>>    1 file changed, 8 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
>>> index 786f775196ae..0f290430ae0e 100644
>>> --- a/drivers/bluetooth/btmtk.c
>>> +++ b/drivers/bluetooth/btmtk.c
>>> @@ -370,7 +370,7 @@ EXPORT_SYMBOL_GPL(btmtk_register_coredump);
>>>    int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff *skb)
>>>    {
>>>    struct btmediatek_data *data = hci_get_priv(hdev);
>>> -int err;
>>> +int err, offset;
>>>    
>>>    if (!IS_ENABLED(CONFIG_DEV_COREDUMP))
>>>    return 0;
>>> @@ -392,15 +392,15 @@ int btmtk_process_coredump(struct hci_dev
>> *hdev, struct sk_buff *skb)
>>>    if (err < 0)
>>>    break;
>>>    data->cd_info.cnt++;
>>> +offset = skb->len - sizeof(MTK_COREDUMP_END);
>>
>> For `sizeof()` shouldn’t you use `size_t`? But that is unsigned of
>> course. Maybe ssize_t then?
>
> yes, it's better to use ssize_t or size_t, I'll change declaratins of
> offset from int to ssize_t.
> 
>>>    
>>>    /* Mediatek coredump data would be more than MTK_COREDUMP_NUM */
>>> -if (data->cd_info.cnt > MTK_COREDUMP_NUM &&
>>> -    skb->len > sizeof(MTK_COREDUMP_END) &&
>>> -    !memcmp((char *)&skb->data[skb->len - sizeof(MTK_COREDUMP_END)],
>>> -    MTK_COREDUMP_END, sizeof(MTK_COREDUMP_END) - 1)) {
>>> -bt_dev_info(hdev, "Mediatek coredump end");
>>> -hci_devcd_complete(hdev);
>>> -}
>>> +if (data->cd_info.cnt > MTK_COREDUMP_NUM && offset > 0)
>>
>> Why not keep it like before, and just add the condition `skb->len <
>> sizeof(MTK_COREDUMP_END)`? The compiler is probably going to optimize
>> so the value is not calculated twice.

> The reason why I send this patch is when I backport devcoredump feature
> to specific project with older kernel version, the compiler might not
> so optimized that it would cause kernel panic when run into memcmp.
> As a result, make sure `skb->len > sizeof(MTK_COREDUMP_END) ` before
> doing memcmp part can avoid null pointer issue.
> Besides, only in condition 'data->cd_info.cnt > MTK_COREDUMP_NUM &&
> offset > 0' need to do memcmp to check the end of coredump. Driver do
> noting with condition `skb->len < sizeof(MTK_COREDUMP_END) ` that
> additional condiction is not really necessary.

Just to avoid misunderstandings, my point, to add the comparison and get 
rid of the variable `offset`.


Kind regards,

Paul


>>> +if (!memcmp((char *)&skb->data[offset], MTK_COREDUMP_END,
>>> +    sizeof(MTK_COREDUMP_END) - 1)) {
>>> +bt_dev_info(hdev, "Mediatek coredump end");
>>> +hci_devcd_complete(hdev);
>>> +}
>>>    
>>>    break;
>>>    }
diff mbox series

Patch

diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
index 786f775196ae..0f290430ae0e 100644
--- a/drivers/bluetooth/btmtk.c
+++ b/drivers/bluetooth/btmtk.c
@@ -370,7 +370,7 @@  EXPORT_SYMBOL_GPL(btmtk_register_coredump);
 int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff *skb)
 {
 	struct btmediatek_data *data = hci_get_priv(hdev);
-	int err;
+	int err, offset;
 
 	if (!IS_ENABLED(CONFIG_DEV_COREDUMP))
 		return 0;
@@ -392,15 +392,15 @@  int btmtk_process_coredump(struct hci_dev *hdev, struct sk_buff *skb)
 		if (err < 0)
 			break;
 		data->cd_info.cnt++;
+		offset = skb->len - sizeof(MTK_COREDUMP_END);
 
 		/* Mediatek coredump data would be more than MTK_COREDUMP_NUM */
-		if (data->cd_info.cnt > MTK_COREDUMP_NUM &&
-		    skb->len > sizeof(MTK_COREDUMP_END) &&
-		    !memcmp((char *)&skb->data[skb->len - sizeof(MTK_COREDUMP_END)],
-			    MTK_COREDUMP_END, sizeof(MTK_COREDUMP_END) - 1)) {
-			bt_dev_info(hdev, "Mediatek coredump end");
-			hci_devcd_complete(hdev);
-		}
+		if (data->cd_info.cnt > MTK_COREDUMP_NUM && offset > 0)
+			if (!memcmp((char *)&skb->data[offset], MTK_COREDUMP_END,
+				    sizeof(MTK_COREDUMP_END) - 1)) {
+				bt_dev_info(hdev, "Mediatek coredump end");
+				hci_devcd_complete(hdev);
+			}
 
 		break;
 	}