linux-kernel-mentees.lists.linuxfoundation.org archive mirror
 help / color / mirror / Atom feed
From: Anmol Karn <anmol.karan123@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: netdev@vger.kernel.org,
	syzbot+0bef568258653cff272f@syzkaller.appspotmail.com,
	syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
	linux-bluetooth@vger.kernel.org, kuba@kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	davem@davemloft.net
Subject: Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt
Date: Mon, 31 Aug 2020 02:12:45 +0530	[thread overview]
Message-ID: <20200830204245.GA249337@Thinkpad> (raw)
In-Reply-To: <20200830173010.GA1872728@kroah.com>

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

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

      reply	other threads:[~2020-08-30 20:42 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-29 12:41 Anmol Karn
2020-08-29 16:57 ` Anmol Karn
2020-08-30  9:18   ` Greg KH
2020-08-30  9:19   ` Greg KH
2020-08-30 12:26     ` Anmol Karn
2020-08-30 17:30       ` Greg KH
2020-08-30 20:42         ` Anmol Karn [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200830204245.GA249337@Thinkpad \
    --to=anmol.karan123@gmail.com \
    --cc=davem@davemloft.net \
    --cc=gregkh@linuxfoundation.org \
    --cc=kuba@kernel.org \
    --cc=linux-bluetooth@vger.kernel.org \
    --cc=linux-kernel-mentees@lists.linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=syzbot+0bef568258653cff272f@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    --subject='Re: [Linux-kernel-mentees] [PATCH] net: bluetooth: Fix null pointer deref in hci_phy_link_complete_evt' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).