[RESEND PATCH v3] Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'

[RESEND PATCH v3] Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'

[Arseniy Krasnov]

Function 'hci_discovery_filter_clear()' frees 'uuids' array and then
sets it to NULL. There is a tiny chance of the following race:

'hci_cmd_sync_work()'

 'update_passive_scan_sync()'

   'hci_update_passive_scan_sync()'

     'hci_discovery_filter_clear()'
       kfree(uuids);

       <-------------------------preempted-------------------------------->
                                           'start_service_discovery()'

                                             'hci_discovery_filter_clear()'
                                               kfree(uuids); // DOUBLE FREE

       <-------------------------preempted-------------------------------->

      uuids = NULL;

To fix it let's add locking around 'kfree()' call and NULL pointer
assignment. Otherwise the following backtrace fires:

[ ] ------------[ cut here ]------------
[ ] kernel BUG at mm/slub.c:547!
[ ] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
[ ] CPU: 3 UID: 0 PID: 246 Comm: bluetoothd Tainted: G O 6.12.19-kernel #1
[ ] Tainted: [O]=OOT_MODULE
[ ] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ ] pc : __slab_free+0xf8/0x348
[ ] lr : __slab_free+0x48/0x348
...
[ ] Call trace:
[ ]  __slab_free+0xf8/0x348
[ ]  kfree+0x164/0x27c
[ ]  start_service_discovery+0x1d0/0x2c0
[ ]  hci_sock_sendmsg+0x518/0x924
[ ]  __sock_sendmsg+0x54/0x60
[ ]  sock_write_iter+0x98/0xf8
[ ]  do_iter_readv_writev+0xe4/0x1c8
[ ]  vfs_writev+0x128/0x2b0
[ ]  do_writev+0xfc/0x118
[ ]  __arm64_sys_writev+0x20/0x2c
[ ]  invoke_syscall+0x68/0xf0
[ ]  el0_svc_common.constprop.0+0x40/0xe0
[ ]  do_el0_svc+0x1c/0x28
[ ]  el0_svc+0x30/0xd0
[ ]  el0t_64_sync_handler+0x100/0x12c
[ ]  el0t_64_sync+0x194/0x198
[ ] Code: 8b0002e6 eb17031f 54fffbe1 d503201f (d4210000) 
[ ] ---[ end trace 0000000000000000 ]---

Fixes: ad383c2c65a5 ("Bluetooth: hci_sync: Enable advertising when LL privacy is enabled")
Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
---
 Changelog v1->v2:
 * Don't call 'hci_dev_lock()' in 'update_passive_scan_sync()' as it
   triggers deadlock. Instead of that - add spinlock which protects
   freeing code.
 Changelog v2->v3:
 * Rebase on current 'bluetooth' repo due to fuzz.

 include/net/bluetooth/hci_core.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 54bfeeaa09959..f8eeb15acdcfa 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -29,6 +29,7 @@
 #include <linux/idr.h>
 #include <linux/leds.h>
 #include <linux/rculist.h>
+#include <linux/spinlock.h>
 
 #include <net/bluetooth/hci.h>
 #include <net/bluetooth/hci_drv.h>
@@ -92,6 +93,7 @@ struct discovery_state {
 	u16			uuid_count;
 	u8			(*uuids)[16];
 	unsigned long		name_resolve_timeout;
+	spinlock_t		lock;
 };
 
 #define SUSPEND_NOTIFIER_TIMEOUT	msecs_to_jiffies(2000) /* 2 seconds */
@@ -878,6 +880,7 @@ static inline void iso_recv(struct hci_conn *hcon, struct sk_buff *skb,
 
 static inline void discovery_init(struct hci_dev *hdev)
 {
+	spin_lock_init(&hdev->discovery.lock);
 	hdev->discovery.state = DISCOVERY_STOPPED;
 	INIT_LIST_HEAD(&hdev->discovery.all);
 	INIT_LIST_HEAD(&hdev->discovery.unknown);
@@ -892,8 +895,11 @@ static inline void hci_discovery_filter_clear(struct hci_dev *hdev)
 	hdev->discovery.report_invalid_rssi = true;
 	hdev->discovery.rssi = HCI_RSSI_INVALID;
 	hdev->discovery.uuid_count = 0;
+
+	spin_lock(&hdev->discovery.lock);
 	kfree(hdev->discovery.uuids);
 	hdev->discovery.uuids = NULL;
+	spin_unlock(&hdev->discovery.lock);
 }
 
 bool hci_discovery_active(struct hci_dev *hdev);
-- 
2.30.1

RE: [RESEND,v3] Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 565 bytes --]

This is an automated email and please do not reply to this email.

Dear Submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
While preparing the CI tests, the patches you submitted couldn't be applied to the current HEAD of the repository.

----- Output -----

error: patch failed: include/net/bluetooth/hci_core.h:29
error: include/net/bluetooth/hci_core.h: patch does not apply
hint: Use 'git am --show-current-patch' to see the failed patch

Please resolve the issue and submit the patches again.


---
Regards,
Linux Bluetooth