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:

quoted

On Sat, Aug 29, 2020 at 10:27:12PM +0530, Anmol Karn wrote:

quoted

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 <redacted>
---
 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?

quoted

quoted

+
 		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
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