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

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

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2081 bytes --]

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=972244

---Test result---

Test Summary:
CheckPatch                    PENDING   0.31 seconds
GitLint                       PENDING   0.28 seconds
SubjectPrefix                 PASS      0.27 seconds
BuildKernel                   PASS      24.57 seconds
CheckAllWarning               PASS      26.79 seconds
CheckSparse                   PASS      29.91 seconds
BuildKernel32                 PASS      23.99 seconds
TestRunnerSetup               PASS      455.15 seconds
TestRunner_l2cap-tester       PASS      25.01 seconds
TestRunner_iso-tester         FAIL      7.83 seconds
TestRunner_bnep-tester        PASS      5.84 seconds
TestRunner_mgmt-tester        FAIL      132.07 seconds
TestRunner_rfcomm-tester      PASS      9.20 seconds
TestRunner_sco-tester         PASS      14.64 seconds
TestRunner_ioctl-tester       PASS      9.81 seconds
TestRunner_mesh-tester        PASS      7.24 seconds
TestRunner_smp-tester         PASS      8.35 seconds
TestRunner_userchan-tester    PASS      6.10 seconds
IncrementalBuild              PENDING   0.73 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: TestRunner_iso-tester - FAIL
Desc: Run iso-tester with test-runner
Output:
No test result found
##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 490, Passed: 485 (99.0%), Failed: 1, Not Run: 4

Failed Test Cases
LL Privacy - Add Device 3 (AL is full)               Failed       0.223 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

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

[Arseniy Krasnov]

Hi, sorry, 2 weeks, pls ping

Thanks

On 15.06.2025 20:17, Arseniy Krasnov wrote:
> 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);

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

[Arseniy Krasnov]

Hi, sorry, 2 weeks, pls ping

Thanks

On 30.06.2025 14:08, Arseniy Krasnov wrote:
> Hi, sorry, 2 weeks, pls ping
> 
> Thanks

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

[Luiz Augusto von Dentz]

Hi Arseniy,

On Wed, Jul 16, 2025 at 11:04 AM Arseniy Krasnov
<avkrasnov@salutedevices.com> wrote:
>
> Hi, sorry, 2 weeks, pls ping

Just resend.

> Thanks
>
> On 30.06.2025 14:08, Arseniy Krasnov wrote:
> > Hi, sorry, 2 weeks, pls ping
> >
> > Thanks



-- 
Luiz Augusto von Dentz