nfc: nci: Fix uninit-value in nci_rx_work()

[PATCH] nfc: nci: Fix uninit-value in nci_rx_work()

Posted by zhanghao 1 year, 4 months ago

Commit e624e6c3e777 ("nfc: Add a virtual nci device driver")
calls alloc_skb() with GFP_KERNEL as the argument flags.The
allocated heap memory was not initialized.This causes KMSAN
to detect an uninitialized value.

Reported-by: syzbot+3da70a0abd7f5765b6ea@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3da70a0abd7f5765b6ea
Fixes: e624e6c3e777 ("nfc: Add a virtual nci device driver")
Link: https://lore.kernel.org/all/000000000000747dd6061a974686@google.com/T/
Signed-off-by: zhanghao <zhanghao1@kylinos.cn>
---
 drivers/nfc/virtual_ncidev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
index 6b89d596ba9a..ae1592db131e 100644
--- a/drivers/nfc/virtual_ncidev.c
+++ b/drivers/nfc/virtual_ncidev.c
@@ -117,7 +117,7 @@ static ssize_t virtual_ncidev_write(struct file *file,
 	struct virtual_nci_dev *vdev = file->private_data;
 	struct sk_buff *skb;
 
-	skb = alloc_skb(count, GFP_KERNEL);
+	skb = alloc_skb(count, GFP_KERNEL|__GFP_ZERO);
 	if (!skb)
 		return -ENOMEM;
 

base-commit: 17712b7ea0756799635ba159cc773082230ed028
-- 
2.39.2

Re: [PATCH] nfc: nci: Fix uninit-value in nci_rx_work()

Posted by Simon Horman 1 year, 4 months ago

On Sat, Aug 03, 2024 at 08:18:17PM +0800, zhanghao wrote:
> Commit e624e6c3e777 ("nfc: Add a virtual nci device driver")
> calls alloc_skb() with GFP_KERNEL as the argument flags.The
> allocated heap memory was not initialized.This causes KMSAN
> to detect an uninitialized value.
> 
> Reported-by: syzbot+3da70a0abd7f5765b6ea@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=3da70a0abd7f5765b6ea

Hi,

I wonder if the problem reported above is caused by accessing packet
data which is past the end of what is copied in virtual_ncidev_write().
I.e. count is unusually short and this is not being detected.

> Fixes: e624e6c3e777 ("nfc: Add a virtual nci device driver")
> Link: https://lore.kernel.org/all/000000000000747dd6061a974686@google.com/T/
> Signed-off-by: zhanghao <zhanghao1@kylinos.cn>
> ---
>  drivers/nfc/virtual_ncidev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
> index 6b89d596ba9a..ae1592db131e 100644
> --- a/drivers/nfc/virtual_ncidev.c
> +++ b/drivers/nfc/virtual_ncidev.c
> @@ -117,7 +117,7 @@ static ssize_t virtual_ncidev_write(struct file *file,
>  	struct virtual_nci_dev *vdev = file->private_data;
>  	struct sk_buff *skb;
>  
> -	skb = alloc_skb(count, GFP_KERNEL);
> +	skb = alloc_skb(count, GFP_KERNEL|__GFP_ZERO);
>  	if (!skb)
>  		return -ENOMEM;

I'm not sure this helps wrt initialising the memory as immediately below there
is;

	if (copy_from_user(skb_put(skb, count), buf, count)) {
		...

Which I assume will initialise count bytes of skb data.

Re: Re: [PATCH] nfc: nci: Fix uninit-value in nci_rx_work()

Posted by zhanghao 1 year, 4 months ago

On 04/08/2024 12:57, Simon Horman wrote:
> > On Sat, Aug 03, 2024 at 08:18:17PM +0800, zhanghao wrote:
> >> Commit e624e6c3e777 ("nfc: Add a virtual nci device driver")
> >> calls alloc_skb() with GFP_KERNEL as the argument flags.The
> >> allocated heap memory was not initialized.This causes KMSAN
> >> to detect an uninitialized value.
> >>
> >> Reported-by: syzbot+3da70a0abd7f5765b6ea@syzkaller.appspotmail.com
> >> Closes: https://syzkaller.appspot.com/bug?extid=3da70a0abd7f5765b6ea
> > 
> > Hi,
> > 
> > I wonder if the problem reported above is caused by accessing packet
> > data which is past the end of what is copied in virtual_ncidev_write().
> > I.e. count is unusually short and this is not being detected.
> > 
Yes, you're right.I debug the kernel and find that skb->data is " ".The 
length is less than 2.Using nci_plen to access skb->data in nci_rx_work()
triggers kmsan to detect access to uninitialized memory.
 
I wonder if I can use skb->len to determine length in the
nci_rx_work().I tested it and there was no problem.
 
> >> Fixes: e624e6c3e777 ("nfc: Add a virtual nci device driver")
> >> Link: https://lore.kernel.org/all/000000000000747dd6061a974686@google.com/T/
> >> Signed-off-by: zhanghao <zhanghao1@kylinos.cn>
> >> ---
> >>  drivers/nfc/virtual_ncidev.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
> >> index 6b89d596ba9a..ae1592db131e 100644
> >> --- a/drivers/nfc/virtual_ncidev.c
> >> +++ b/drivers/nfc/virtual_ncidev.c
> >> @@ -117,7 +117,7 @@ static ssize_t virtual_ncidev_write(struct file *file,
> >>  	struct virtual_nci_dev *vdev = file->private_data;
> >>  	struct sk_buff *skb;
> >>  
> >> -	skb = alloc_skb(count, GFP_KERNEL);
> >> +	skb = alloc_skb(count, GFP_KERNEL|__GFP_ZERO);
> >>  	if (!skb)
> >>  		return -ENOMEM;
> > 
> > I'm not sure this helps wrt initialising the memory as immediately below there
> > is;
> > 
> > 	if (copy_from_user(skb_put(skb, count), buf, count)) {
> > 		...
> > 
> > Which I assume will initialise count bytes of skb data.
> 
> Yeah, this looks like hiding the real issue.
> 
> Best regards,
> Krzysztof

Re: [PATCH] nfc: nci: Fix uninit-value in nci_rx_work()

Posted by Krzysztof Kozlowski 1 year, 4 months ago

On 04/08/2024 12:57, Simon Horman wrote:
> On Sat, Aug 03, 2024 at 08:18:17PM +0800, zhanghao wrote:
>> Commit e624e6c3e777 ("nfc: Add a virtual nci device driver")
>> calls alloc_skb() with GFP_KERNEL as the argument flags.The
>> allocated heap memory was not initialized.This causes KMSAN
>> to detect an uninitialized value.
>>
>> Reported-by: syzbot+3da70a0abd7f5765b6ea@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=3da70a0abd7f5765b6ea
> 
> Hi,
> 
> I wonder if the problem reported above is caused by accessing packet
> data which is past the end of what is copied in virtual_ncidev_write().
> I.e. count is unusually short and this is not being detected.
> 
>> Fixes: e624e6c3e777 ("nfc: Add a virtual nci device driver")
>> Link: https://lore.kernel.org/all/000000000000747dd6061a974686@google.com/T/
>> Signed-off-by: zhanghao <zhanghao1@kylinos.cn>
>> ---
>>  drivers/nfc/virtual_ncidev.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
>> index 6b89d596ba9a..ae1592db131e 100644
>> --- a/drivers/nfc/virtual_ncidev.c
>> +++ b/drivers/nfc/virtual_ncidev.c
>> @@ -117,7 +117,7 @@ static ssize_t virtual_ncidev_write(struct file *file,
>>  	struct virtual_nci_dev *vdev = file->private_data;
>>  	struct sk_buff *skb;
>>  
>> -	skb = alloc_skb(count, GFP_KERNEL);
>> +	skb = alloc_skb(count, GFP_KERNEL|__GFP_ZERO);
>>  	if (!skb)
>>  		return -ENOMEM;
> 
> I'm not sure this helps wrt initialising the memory as immediately below there
> is;
> 
> 	if (copy_from_user(skb_put(skb, count), buf, count)) {
> 		...
> 
> Which I assume will initialise count bytes of skb data.

Yeah, this looks like hiding the real issue.

Best regards,
Krzysztof