Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv_monitor()

KASAN reports that there's a use-after-free in
hci_remove_adv_monitor(). Trawling through the disassembly, you can
see that the complaint is from the access in bt_dev_dbg() under the
HCI_ADV_MONITOR_EXT_MSFT case. The problem case happens because
msft_remove_monitor() can end up freeing the monitor
structure. Specifically:
  hci_remove_adv_monitor() ->
  msft_remove_monitor() ->
  msft_remove_monitor_sync() ->
  msft_le_cancel_monitor_advertisement_cb() ->
  hci_free_adv_monitor()

Let's fix the problem by just stashing the relevant data when it's
still valid.

Fixes: 7cf5c2978f23 ("Bluetooth: hci_sync: Refactor remove Adv Monitor")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 net/bluetooth/hci_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Hi Douglas,

On Fri, Jun 30, 2023 at 2:40 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> KASAN reports that there's a use-after-free in
> hci_remove_adv_monitor(). Trawling through the disassembly, you can
> see that the complaint is from the access in bt_dev_dbg() under the
> HCI_ADV_MONITOR_EXT_MSFT case. The problem case happens because
> msft_remove_monitor() can end up freeing the monitor
> structure. Specifically:
>   hci_remove_adv_monitor() ->
>   msft_remove_monitor() ->
>   msft_remove_monitor_sync() ->
>   msft_le_cancel_monitor_advertisement_cb() ->
>   hci_free_adv_monitor()
>
> Let's fix the problem by just stashing the relevant data when it's
> still valid.
>
> Fixes: 7cf5c2978f23 ("Bluetooth: hci_sync: Refactor remove Adv Monitor")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
>  net/bluetooth/hci_core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 48917c68358d..dbb2043a9112 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -1972,6 +1972,7 @@ static int hci_remove_adv_monitor(struct hci_dev *hdev,
>                                   struct adv_monitor *monitor)
>  {
>         int status = 0;
> +       int handle;
>
>         switch (hci_get_adv_monitor_offload_ext(hdev)) {
>         case HCI_ADV_MONITOR_EXT_NONE: /* also goes here when powered off */
> @@ -1980,9 +1981,10 @@ static int hci_remove_adv_monitor(struct hci_dev *hdev,
>                 goto free_monitor;
>
>         case HCI_ADV_MONITOR_EXT_MSFT:
> +               handle = monitor->handle;
>                 status = msft_remove_monitor(hdev, monitor);
>                 bt_dev_dbg(hdev, "%s remove monitor %d msft status %d",
> -                          hdev->name, monitor->handle, status);
> +                          hdev->name, handle, status);

Just move the call to bt_dev_dbg under msft_remove_monitor, also there
is no reason to print hdev->name since bt_dev_dbg already does that so
while at it we can probably fix this as well.

>                 break;
>         }
>
> --
> 2.41.0.255.g8b1d071c50-goog
>

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=761687

---Test result---

Test Summary:
CheckPatch                    PASS      0.82 seconds
GitLint                       PASS      0.39 seconds
SubjectPrefix                 PASS      0.14 seconds
BuildKernel                   PASS      40.34 seconds
CheckAllWarning               PASS      43.82 seconds
CheckSparse                   PASS      49.54 seconds
CheckSmatch                   PASS      133.50 seconds
BuildKernel32                 PASS      38.92 seconds
TestRunnerSetup               PASS      548.39 seconds
TestRunner_l2cap-tester       PASS      16.87 seconds
TestRunner_iso-tester         PASS      30.80 seconds
TestRunner_bnep-tester        PASS      7.45 seconds
TestRunner_mgmt-tester        PASS      158.27 seconds
TestRunner_rfcomm-tester      PASS      11.48 seconds
TestRunner_sco-tester         PASS      12.65 seconds
TestRunner_ioctl-tester       PASS      12.88 seconds
TestRunner_mesh-tester        PASS      9.09 seconds
TestRunner_smp-tester         PASS      10.63 seconds
TestRunner_userchan-tester    PASS      7.63 seconds
IncrementalBuild              PASS      36.82 seconds



---
Regards,
Linux Bluetooth