[Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Anmol Karn]

Fix null pointer deref in hci_phy_link_complete_evt, there was no checking there for
the hcon->amp_mgr->l2cap_conn->hconn, and also in hci_cmd_work, for
hdev->sent_cmd. 

To fix this issue Add pointer checking in hci_cmd_work and
hci_phy_link_complete_evt.
[Linux-next-20200827]

Reported-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
---
 net/bluetooth/hci_core.c  | 4 ++++
 net/bluetooth/hci_event.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 68bfe57b6625..533048d2a624 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4922,6 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
 
 		kfree_skb(hdev->sent_cmd);
 
+		if(hdev->sent_cmd) {
+			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
+		}
+
 		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
 		if (hdev->sent_cmd) {
 			if (hci_req_status_pend(hdev))
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 4b7fc430793c..c621c8a20ea4 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
 		hci_dev_unlock(hdev);
 		return;
 	}
+	if(!(hcon->amp_mgr->l2cap_conn->hcon)) {
+		hci_dev_unlock(hdev);
+		return;
+	}
 
 	bredr_hcon = hcon->amp_mgr->l2cap_conn->hcon;
 
-- 
2.28.0

[Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Anmol Karn]

Fix null pointer deref in hci_phy_link_complete_evt, there was no 
checking there for the hcon->amp_mgr->l2cap_conn->hconn, and also 
in hci_cmd_work, for hdev->sent_cmd.

To fix this issue Add pointer checking in hci_cmd_work and
hci_phy_link_complete_evt.
[Linux-next-20200827]

This patch corrected some mistakes from previous patch.

Reported-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
---
 net/bluetooth/hci_core.c  | 5 ++++-
 net/bluetooth/hci_event.c | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 68bfe57b6625..996efd654e7a 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4922,7 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
 
 		kfree_skb(hdev->sent_cmd);
 
-		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
+		if (hdev->sent_cmd) {
+			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
+		}
+
 		if (hdev->sent_cmd) {
 			if (hci_req_status_pend(hdev))
 				hci_dev_set_flag(hdev, HCI_CMD_PENDING);
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 4b7fc430793c..1e7d9bee9111 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
 		hci_dev_unlock(hdev);
 		return;
 	}
+	if (!(hcon->amp_mgr->l2cap_conn->hcon)) {
+		hci_dev_unlock(hdev);
+		return;
+	}
 
 	bredr_hcon = hcon->amp_mgr->l2cap_conn->hcon;
 
-- 
2.28.0

Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Greg KH]

On Sat, Aug 29, 2020 at 10:27:12PM +0530, Anmol Karn wrote:
> Fix null pointer deref in hci_phy_link_complete_evt, there was no 
> checking there for the hcon->amp_mgr->l2cap_conn->hconn, and also 
> in hci_cmd_work, for hdev->sent_cmd.
> 
> To fix this issue Add pointer checking in hci_cmd_work and
> hci_phy_link_complete_evt.
> [Linux-next-20200827]
> 
> This patch corrected some mistakes from previous patch.

So this is a v2?  That should go below the --- line, right?  And you
should have a v2 in the subject line like the documentation asks?

Can you redo this please?

thanks,

greg k-h

Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Greg KH]

On Sat, Aug 29, 2020 at 10:27:12PM +0530, Anmol Karn wrote:
> Fix null pointer deref in hci_phy_link_complete_evt, there was no 
> checking there for the hcon->amp_mgr->l2cap_conn->hconn, and also 
> in hci_cmd_work, for hdev->sent_cmd.
> 
> To fix this issue Add pointer checking in hci_cmd_work and
> hci_phy_link_complete_evt.
> [Linux-next-20200827]
> 
> This patch corrected some mistakes from previous patch.
> 
> Reported-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
> Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
> ---
>  net/bluetooth/hci_core.c  | 5 ++++-
>  net/bluetooth/hci_event.c | 4 ++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 68bfe57b6625..996efd654e7a 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -4922,7 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
>  
>  		kfree_skb(hdev->sent_cmd);
>  
> -		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> +		if (hdev->sent_cmd) {
> +			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> +		}

How can sent_cmd be NULL here?  Are you sure something previous to this
shouldn't be fixed instead?


> +
>  		if (hdev->sent_cmd) {
>  			if (hci_req_status_pend(hdev))
>  				hci_dev_set_flag(hdev, HCI_CMD_PENDING);
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 4b7fc430793c..1e7d9bee9111 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
>  		hci_dev_unlock(hdev);
>  		return;
>  	}
> +	if (!(hcon->amp_mgr->l2cap_conn->hcon)) {
> +		hci_dev_unlock(hdev);
> +		return;
> +	}

How can this be triggered?

thanks,

greg k-h

Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Anmol Karn]

On Sun, Aug 30, 2020 at 11:19:17AM +0200, Greg KH wrote:
> On Sat, Aug 29, 2020 at 10:27:12PM +0530, Anmol Karn wrote:
> > Fix null pointer deref in hci_phy_link_complete_evt, there was no 
> > checking there for the hcon->amp_mgr->l2cap_conn->hconn, and also 
> > in hci_cmd_work, for hdev->sent_cmd.
> > 
> > To fix this issue Add pointer checking in hci_cmd_work and
> > hci_phy_link_complete_evt.
> > [Linux-next-20200827]
> > 
> > This patch corrected some mistakes from previous patch.
> > 
> > Reported-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com
> > Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
> > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
> > ---
> >  net/bluetooth/hci_core.c  | 5 ++++-
> >  net/bluetooth/hci_event.c | 4 ++++
> >  2 files changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index 68bfe57b6625..996efd654e7a 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -4922,7 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
> >  
> >  		kfree_skb(hdev->sent_cmd);
> >  
> > -		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> > +		if (hdev->sent_cmd) {
> > +			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> > +		}
> 
> How can sent_cmd be NULL here?  Are you sure something previous to this
> shouldn't be fixed instead?

Sir, sent_cmd was freed before this condition check, thats why i checked it,

i think i should check it before the free of hdev->sent_cmd like,

if (hdev->sent_cmd)
	kfree_skb(hdev->sent_cmd);

what's your opininon on this.

> 
> 
> > +
> >  		if (hdev->sent_cmd) {
> >  			if (hci_req_status_pend(hdev))
> >  				hci_dev_set_flag(hdev, HCI_CMD_PENDING);
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 4b7fc430793c..1e7d9bee9111 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
> >  		hci_dev_unlock(hdev);
> >  		return;
> >  	}
> > +	if (!(hcon->amp_mgr->l2cap_conn->hcon)) {
> > +		hci_dev_unlock(hdev);
> > +		return;
> > +	}
> 
> How can this be triggered?

syzbot showed that this line is accessed irrespective of the null value it contains, so  added a 
pointer check for that.

please give some opinions on this,

if (!bredr_hcon) {
	hci_dev_unlock(hdev);
        return;
}

Thanks,
Anmol Karn

Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Greg KH]

On Sun, Aug 30, 2020 at 05:56:23PM +0530, Anmol Karn wrote:
> On Sun, Aug 30, 2020 at 11:19:17AM +0200, Greg KH wrote:
> > On Sat, Aug 29, 2020 at 10:27:12PM +0530, Anmol Karn wrote:
> > > Fix null pointer deref in hci_phy_link_complete_evt, there was no 
> > > checking there for the hcon->amp_mgr->l2cap_conn->hconn, and also 
> > > in hci_cmd_work, for hdev->sent_cmd.
> > > 
> > > To fix this issue Add pointer checking in hci_cmd_work and
> > > hci_phy_link_complete_evt.
> > > [Linux-next-20200827]
> > > 
> > > This patch corrected some mistakes from previous patch.
> > > 
> > > Reported-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com
> > > Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
> > > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
> > > ---
> > >  net/bluetooth/hci_core.c  | 5 ++++-
> > >  net/bluetooth/hci_event.c | 4 ++++
> > >  2 files changed, 8 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > > index 68bfe57b6625..996efd654e7a 100644
> > > --- a/net/bluetooth/hci_core.c
> > > +++ b/net/bluetooth/hci_core.c
> > > @@ -4922,7 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
> > >  
> > >  		kfree_skb(hdev->sent_cmd);
> > >  
> > > -		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> > > +		if (hdev->sent_cmd) {
> > > +			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> > > +		}
> > 
> > How can sent_cmd be NULL here?  Are you sure something previous to this
> > shouldn't be fixed instead?
> 
> Sir, sent_cmd was freed before this condition check, thats why i checked it,

But it can not be NULL at that point in time, as nothing set it to NULL,
correct?

> i think i should check it before the free of hdev->sent_cmd like,
> 
> if (hdev->sent_cmd)
> 	kfree_skb(hdev->sent_cmd);

No, that's not needed.

What is the problem with these lines that you are trying to solve?

> > > +
> > >  		if (hdev->sent_cmd) {
> > >  			if (hci_req_status_pend(hdev))
> > >  				hci_dev_set_flag(hdev, HCI_CMD_PENDING);
> > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > > index 4b7fc430793c..1e7d9bee9111 100644
> > > --- a/net/bluetooth/hci_event.c
> > > +++ b/net/bluetooth/hci_event.c
> > > @@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
> > >  		hci_dev_unlock(hdev);
> > >  		return;
> > >  	}
> > > +	if (!(hcon->amp_mgr->l2cap_conn->hcon)) {
> > > +		hci_dev_unlock(hdev);
> > > +		return;
> > > +	}
> > 
> > How can this be triggered?
> 
> syzbot showed that this line is accessed irrespective of the null value it contains, so  added a 
> pointer check for that.

But does hcon->amp_mgr->l2cap_conn->hcon become NULL here?

thanks,

greg k-h

Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt

[Anmol Karn]

On Sun, Aug 30, 2020 at 07:30:10PM +0200, Greg KH wrote:
> On Sun, Aug 30, 2020 at 05:56:23PM +0530, Anmol Karn wrote:
> > On Sun, Aug 30, 2020 at 11:19:17AM +0200, Greg KH wrote:
> > > On Sat, Aug 29, 2020 at 10:27:12PM +0530, Anmol Karn wrote:
> > > > Fix null pointer deref in hci_phy_link_complete_evt, there was no 
> > > > checking there for the hcon->amp_mgr->l2cap_conn->hconn, and also 
> > > > in hci_cmd_work, for hdev->sent_cmd.
> > > > 
> > > > To fix this issue Add pointer checking in hci_cmd_work and
> > > > hci_phy_link_complete_evt.
> > > > [Linux-next-20200827]
> > > > 
> > > > This patch corrected some mistakes from previous patch.
> > > > 
> > > > Reported-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com
> > > > Link: https://syzkaller.appspot.com/bug?id=0d93140da5a82305a66a136af99b088b75177b99
> > > > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
> > > > ---
> > > >  net/bluetooth/hci_core.c  | 5 ++++-
> > > >  net/bluetooth/hci_event.c | 4 ++++
> > > >  2 files changed, 8 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > > > index 68bfe57b6625..996efd654e7a 100644
> > > > --- a/net/bluetooth/hci_core.c
> > > > +++ b/net/bluetooth/hci_core.c
> > > > @@ -4922,7 +4922,10 @@ static void hci_cmd_work(struct work_struct *work)
> > > >  
> > > >  		kfree_skb(hdev->sent_cmd);
> > > >  
> > > > -		hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> > > > +		if (hdev->sent_cmd) {
> > > > +			hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
> > > > +		}
> > > 
> > > How can sent_cmd be NULL here?  Are you sure something previous to this
> > > shouldn't be fixed instead?
> > 
> > Sir, sent_cmd was freed before this condition check, thats why i checked it,
> 
> But it can not be NULL at that point in time, as nothing set it to NULL,
> correct?
> 
> > i think i should check it before the free of hdev->sent_cmd like,
> > 
> > if (hdev->sent_cmd)
> > 	kfree_skb(hdev->sent_cmd);
> 
> No, that's not needed.
> 
> What is the problem with these lines that you are trying to solve?
> 
> > > > +
> > > >  		if (hdev->sent_cmd) {
> > > >  			if (hci_req_status_pend(hdev))
> > > >  				hci_dev_set_flag(hdev, HCI_CMD_PENDING);
> > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > > > index 4b7fc430793c..1e7d9bee9111 100644
> > > > --- a/net/bluetooth/hci_event.c
> > > > +++ b/net/bluetooth/hci_event.c
> > > > @@ -4941,6 +4941,10 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev,
> > > >  		hci_dev_unlock(hdev);
> > > >  		return;
> > > >  	}
> > > > +	if (!(hcon->amp_mgr->l2cap_conn->hcon)) {
> > > > +		hci_dev_unlock(hdev);
> > > > +		return;
> > > > +	}
> > > 
> > > How can this be triggered?
> > 
> > syzbot showed that this line is accessed irrespective of the null value it contains, so  added a 
> > pointer check for that.
> 
> But does hcon->amp_mgr->l2cap_conn->hcon become NULL here?

Sir, according to the report obtained by running decode_stacktrace on logs there is something getting null at this line, after verifying the buggy address i thought
it would be better to check this whole line. 

will dig more deeper into this and will make appropriate changes in the next version, thanks for review.

Anmol Karn