[PATCH v3 1/2] Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv_monitor()

[PATCH v3 1/2] Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv_monitor()

[Douglas Anderson]

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>
---

Changes in v3:
- Back to v1 where we stash the handle in a local.

Changes in v2:
- Move the print, don't stash handle in a local.

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

[PATCH v3 2/2] Bluetooth: hci_sync: Don't double print name in add/remove adv_monitor

[Douglas Anderson]

The hci_add_adv_monitor() hci_remove_adv_monitor() functions call
bt_dev_dbg() to print some debug statements. The bt_dev_dbg() macro
automatically adds in the device's name. That means that we shouldn't
include the name in the bt_dev_dbg() calls.

Suggested-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

(no changes since v2)

Changes in v2:
- ("Don't double print name...") new for v2.

 net/bluetooth/hci_core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index dbb2043a9112..de15a2c77e9f 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1949,14 +1949,14 @@ int hci_add_adv_monitor(struct hci_dev *hdev, struct adv_monitor *monitor)
 
 	switch (hci_get_adv_monitor_offload_ext(hdev)) {
 	case HCI_ADV_MONITOR_EXT_NONE:
-		bt_dev_dbg(hdev, "%s add monitor %d status %d", hdev->name,
+		bt_dev_dbg(hdev, "add monitor %d status %d",
 			   monitor->handle, status);
 		/* Message was not forwarded to controller - not an error */
 		break;
 
 	case HCI_ADV_MONITOR_EXT_MSFT:
 		status = msft_add_monitor_pattern(hdev, monitor);
-		bt_dev_dbg(hdev, "%s add monitor %d msft status %d", hdev->name,
+		bt_dev_dbg(hdev, "add monitor %d msft status %d",
 			   monitor->handle, status);
 		break;
 	}
@@ -1976,15 +1976,15 @@ static int hci_remove_adv_monitor(struct hci_dev *hdev,
 
 	switch (hci_get_adv_monitor_offload_ext(hdev)) {
 	case HCI_ADV_MONITOR_EXT_NONE: /* also goes here when powered off */
-		bt_dev_dbg(hdev, "%s remove monitor %d status %d", hdev->name,
+		bt_dev_dbg(hdev, "remove monitor %d status %d",
 			   monitor->handle, status);
 		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, handle, status);
+		bt_dev_dbg(hdev, "remove monitor %d msft status %d",
+			   handle, status);
 		break;
 	}
 
-- 
2.41.0.255.g8b1d071c50-goog

Re: [PATCH v3 1/2] Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv_monitor()

[patchwork-bot+bluetooth]

Hello:

This series was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Fri, 30 Jun 2023 15:33:14 -0700 you 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()
> 
> [...]

Here is the summary with links:
  - [v3,1/2] Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv_monitor()
    https://git.kernel.org/bluetooth/bluetooth-next/c/2648c5eb33ca
  - [v3,2/2] Bluetooth: hci_sync: Don't double print name in add/remove adv_monitor
    https://git.kernel.org/bluetooth/bluetooth-next/c/22d2055a576d

You are awesome, thank you!
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