| Message ID | 20200910043424.19894-1-anmol.karan123@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [Linux-kernel-mentees] net: bluetooth: Fix null pointer dereference in hci_event_packet() | expand |
On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote: > Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' > as NULL. Fix it by adding pointer check for it. > > Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> > --- > net/bluetooth/hci_event.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 4b7fc430793c..871e16804433 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > return; > } > > + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { > + hci_dev_unlock(hdev); > + return; > + } > + In patches that fix a NULL pointer dereference, please include a brief explanation of why the pointer can be NULL, including what it means semantically; and why the proposed change is the best fix for the problem. Also, why IS_ERR_OR_NULL()? - Eric
On Wed, Sep 09, 2020 at 10:06:59PM -0700, Eric Biggers wrote: > On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote: > > Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' > > as NULL. Fix it by adding pointer check for it. > > > > Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com > > Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f > > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> > > --- > > net/bluetooth/hci_event.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > > index 4b7fc430793c..871e16804433 100644 > > --- a/net/bluetooth/hci_event.c > > +++ b/net/bluetooth/hci_event.c > > @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > > return; > > } > > > > + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { > > + hci_dev_unlock(hdev); > > + return; > > + } > > + > Hello Sir, > In patches that fix a NULL pointer dereference, please include a brief > explanation of why the pointer can be NULL, including what it means > semantically; and why the proposed change is the best fix for the problem. > I will surely add more explaination in v2. > Also, why IS_ERR_OR_NULL()? > I used IS_ERR_OR_NULL() to check if the 'hcon->amp_mgr' is a valid pointer or not, and unregister the 'hcon' and signal error, but will make changes in v2 with only NULL check included, if you think it's incorrect to use IS_ERR check here along with NULL. Thanks, Anmol Karn
On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote: > Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' > as NULL. Fix it by adding pointer check for it. > > Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> > --- > net/bluetooth/hci_event.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 4b7fc430793c..871e16804433 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > return; > } > > + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { It can't be an error pointer. Shouldn't we call hci_conn_del() on this path? Try to find the Fixes tag to explain how this bug was introduced. (Don't rush to send a v2. The patch requires quite a bit more digging and detective work before it is ready). > + hci_dev_unlock(hdev); > + return; > + } > + > if (ev->status) { > hci_conn_del(hcon); > hci_dev_unlock(hdev); regards, dan carpenter
On Thu, Sep 10, 2020 at 01:49:18PM +0300, Dan Carpenter wrote: > On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote: > > Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' > > as NULL. Fix it by adding pointer check for it. > > > > Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com > > Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f > > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> > > --- > > net/bluetooth/hci_event.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > > index 4b7fc430793c..871e16804433 100644 > > --- a/net/bluetooth/hci_event.c > > +++ b/net/bluetooth/hci_event.c > > @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > > return; > > } > > > > + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { > > It can't be an error pointer. Shouldn't we call hci_conn_del() on this > path? Try to find the Fixes tag to explain how this bug was introduced. > > (Don't rush to send a v2. The patch requires quite a bit more digging > and detective work before it is ready). > > > + hci_dev_unlock(hdev); > > + return; > > + } > > + > > if (ev->status) { > > hci_conn_del(hcon); > > hci_dev_unlock(hdev); > > regards, > dan carpenter > Sure sir, will work on it, thanks for your review. Anmol Karn
On Thu, Sep 10, 2020 at 01:49:18PM +0300, Dan Carpenter wrote: > On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote: > > Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' > > as NULL. Fix it by adding pointer check for it. > > > > Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com > > Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f > > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> > > --- > > net/bluetooth/hci_event.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > > index 4b7fc430793c..871e16804433 100644 > > --- a/net/bluetooth/hci_event.c > > +++ b/net/bluetooth/hci_event.c > > @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > > return; > > } > > > > + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { > > It can't be an error pointer. Shouldn't we call hci_conn_del() on this > path? Try to find the Fixes tag to explain how this bug was introduced. > > (Don't rush to send a v2. The patch requires quite a bit more digging > and detective work before it is ready). > > > + hci_dev_unlock(hdev); > > + return; > > + } > > + > > if (ev->status) { > > hci_conn_del(hcon); > > hci_dev_unlock(hdev); > > regards, > dan carpenter > Sir, I need little advice in continuing with this Patch, I have looked into the Bisected logs and the problem occurs from this commit: 941992d29447 ("ethernet: amd: use IS_ENABLED() instead of checking for built-in or module") Here is a diff of patch which i modified from last patch, diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 4b7fc430793c..6ce435064e0b 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4936,6 +4936,12 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, return; } + if (!hcon->amp_mgr) { + hci_conn_del(hcon); + hci_dev_unlock(hdev); + return; + } + if (ev->status) { hci_conn_del(hcon); hci_dev_unlock(hdev); The value of 'hcon->amp_mgr' getting NULL due to hci_conn_hash_lookup_handle call , and there is not any checks there for the members of hcon, which enables hci_phy_link_complete_evt() to dereference 'hcon->amp_mgr' as NULL. please suggest improvements to this patch. Regards, Anmol
On Sat, Sep 12, 2020 at 02:40:28PM +0530, Anmol Karn wrote: > On Thu, Sep 10, 2020 at 01:49:18PM +0300, Dan Carpenter wrote: > > On Thu, Sep 10, 2020 at 10:04:24AM +0530, Anmol Karn wrote: > > > Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' > > > as NULL. Fix it by adding pointer check for it. > > > > > > Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com > > > Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f > > > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> > > > --- > > > net/bluetooth/hci_event.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > > > index 4b7fc430793c..871e16804433 100644 > > > --- a/net/bluetooth/hci_event.c > > > +++ b/net/bluetooth/hci_event.c > > > @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > > > return; > > > } > > > > > > + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { > > > > It can't be an error pointer. Shouldn't we call hci_conn_del() on this > > path? Try to find the Fixes tag to explain how this bug was introduced. > > > > (Don't rush to send a v2. The patch requires quite a bit more digging > > and detective work before it is ready). > > > > > + hci_dev_unlock(hdev); > > > + return; > > > + } > > > + > > > if (ev->status) { > > > hci_conn_del(hcon); > > > hci_dev_unlock(hdev); > > > > regards, > > dan carpenter > > > > Sir, > > I need little advice in continuing with this Patch, > > I have looked into the Bisected logs and the problem occurs from this commit: > > 941992d29447 ("ethernet: amd: use IS_ENABLED() instead of checking for built-in or module") > That's just the patch which made the code testable by syzbot. It didn't introduce the bug. > > Here is a diff of patch which i modified from last patch, > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 4b7fc430793c..6ce435064e0b 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -4936,6 +4936,12 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > return; > } > > + if (!hcon->amp_mgr) { > + hci_conn_del(hcon); > + hci_dev_unlock(hdev); I have no idea if calling hci_conn_del() is really the correct, thing. I don't know the code at all. Anyway, do some research and figure out for sure what the correct thing is. Also look for similar bugs in other places where hcon->amp_mgr is dereferenced. For example, amp_read_loc_assoc_final_data() seems to have a similar bug. regards, dan carpenter
Hello Sir, > > I have looked into the Bisected logs and the problem occurs from this commit: > > > > 941992d29447 ("ethernet: amd: use IS_ENABLED() instead of checking for built-in or module") > > > > That's just the patch which made the code testable by syzbot. It didn't > introduce the bug. > > > > > Here is a diff of patch which i modified from last patch, > > > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > > index 4b7fc430793c..6ce435064e0b 100644 > > --- a/net/bluetooth/hci_event.c > > +++ b/net/bluetooth/hci_event.c > > @@ -4936,6 +4936,12 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, > > return; > > } > > > > + if (!hcon->amp_mgr) { > > + hci_conn_del(hcon); > > + hci_dev_unlock(hdev); > > I have no idea if calling hci_conn_del() is really the correct, thing. > I don't know the code at all. Anyway, do some research and figure out > for sure what the correct thing is. I have created my patch on the basis of the already applied conditions handling in this function, i.e whenever NULL dereference occurs, connection cleanup is required hence, hci_conn_del() is used here. Will see if anything else could be done. > > Also look for similar bugs in other places where hcon->amp_mgr is > dereferenced. For example, amp_read_loc_assoc_final_data() seems to > have a similar bug. > Sure sir will look into it. > regards, > dan carpenter > Thanks, Anmol
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 4b7fc430793c..871e16804433 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4936,6 +4936,11 @@ static void hci_phy_link_complete_evt(struct hci_dev *hdev, return; } + if (IS_ERR_OR_NULL(hcon->amp_mgr)) { + hci_dev_unlock(hdev); + return; + } + if (ev->status) { hci_conn_del(hcon); hci_dev_unlock(hdev);
Prevent hci_phy_link_complete_evt() from dereferencing 'hcon->amp_mgr' as NULL. Fix it by adding pointer check for it. Reported-and-tested-by: syzbot+0bef568258653cff272f@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=0bef568258653cff272f Signed-off-by: Anmol Karn <anmol.karan123@gmail.com> --- net/bluetooth/hci_event.c | 5 +++++ 1 file changed, 5 insertions(+)