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Sun, 30 Aug 2020 13:42:51 -0700 (PDT) Date: Mon, 31 Aug 2020 02:12:45 +0530 From: Anmol Karn To: Greg KH Message-ID: <20200830204245.GA249337@Thinkpad> References: <20200829124112.227133-1-anmol.karan123@gmail.com> <20200829165712.229437-1-anmol.karan123@gmail.com> <20200830091917.GB122343@kroah.com> <20200830122623.GA235919@Thinkpad> <20200830173010.GA1872728@kroah.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200830173010.GA1872728@kroah.com> 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 X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" 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 > > > > --- > > > > 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