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Message-ID: <CABBYNZJ21uzmWiksD6CLDBuEe2pfPzFGsbn5quZ4edz3W0Wv=g@mail.gmail.com>
Date: Mon, 29 Apr 2024 12:43:43 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Sungwoo Kim <iam@...g-woo.kim>
Cc: daveti@...due.edu, Marcel Holtmann <marcel@...tmann.org>,
Johan Hedberg <johan.hedberg@...il.com>, linux-bluetooth@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Bluetooth: msft: fix slab-use-after-free in msft_do_close()
Hi Sungwoo,
On Sat, Apr 27, 2024 at 10:03 PM Sungwoo Kim <iam@...g-woo.kim> wrote:
>
> Hi, could you review this patch?
> Now *not static* msft functions hold and put hdev->msft_data.
> It prevents from potential and real use-after-free bugs.
>
> How msft is used after freed:
>
> [use]
> msft_do_close()
> msft = hdev->msft_data;
> if (!msft) ...(1) <- passed.
> return;
> mutex_lock(&msft->filter_lock); ...(4) <- used after freed.
>
> [free]
> msft_unregister()
> msft = hdev->msft_data;
> hdev->msft_data = NULL; ...(2)
> kfree(msft); ...(3) <- msft is freed.
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/mutex.c:587 [inline]
> BUG: KASAN: slab-use-after-free in __mutex_lock+0x8f/0xc30 kernel/locking/mutex.c:752
> Read of size 8 at addr ffff888106cbbca8 by task kworker/u5:2/309
>
> CPU: 0 PID: 309 Comm: kworker/u5:2 Not tainted 6.9.0-rc5+ #5
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> Workqueue: hci4 hci_error_reset
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x140 lib/dump_stack.c:114
> print_address_description mm/kasan/report.c:377 [inline]
> print_report+0x191/0x560 mm/kasan/report.c:488
> kasan_report+0xe2/0x120 mm/kasan/report.c:601
> __asan_report_load8_noabort+0x18/0x20 mm/kasan/report_generic.c:381
> __mutex_lock_common kernel/locking/mutex.c:587 [inline]
> __mutex_lock+0x8f/0xc30 kernel/locking/mutex.c:752
> mutex_lock_nested+0x1f/0x30 kernel/locking/mutex.c:804
> msft_do_close+0x292/0x700 net/bluetooth/msft.c:694
> hci_dev_close_sync+0x906/0xf10 net/bluetooth/hci_sync.c:5168
> hci_dev_do_close net/bluetooth/hci_core.c:554 [inline]
> hci_error_reset+0x152/0x410 net/bluetooth/hci_core.c:1091
> process_one_work kernel/workqueue.c:3254 [inline]
> process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335
> worker_thread+0x926/0xe70 kernel/workqueue.c:3416
> kthread+0x2e3/0x380 kernel/kthread.c:388
> ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> </TASK>
>
> Allocated by task 7328:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x30/0x70 mm/kasan/common.c:68
> kasan_save_alloc_info+0x3c/0x50 mm/kasan/generic.c:565
> poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
> __kasan_kmalloc+0xa2/0xc0 mm/kasan/common.c:387
> kasan_kmalloc include/linux/kasan.h:211 [inline]
> kmalloc_trace+0x20c/0x3e0 mm/slub.c:3997
> kmalloc include/linux/slab.h:628 [inline]
> kzalloc include/linux/slab.h:749 [inline]
> msft_register+0x66/0x1d0 net/bluetooth/msft.c:760
> hci_register_dev+0x85e/0x9a0 net/bluetooth/hci_core.c:2737
> __vhci_create_device drivers/bluetooth/hci_vhci.c:438 [inline]
> vhci_create_device+0x390/0x720 drivers/bluetooth/hci_vhci.c:480
> vhci_get_user drivers/bluetooth/hci_vhci.c:537 [inline]
> vhci_write+0x39b/0x460 drivers/bluetooth/hci_vhci.c:617
> call_write_iter include/linux/fs.h:2110 [inline]
> new_sync_write fs/read_write.c:497 [inline]
> vfs_write+0x8eb/0xb50 fs/read_write.c:590
> ksys_write+0x106/0x1f0 fs/read_write.c:643
> __do_sys_write fs/read_write.c:655 [inline]
> __se_sys_write fs/read_write.c:652 [inline]
> __x64_sys_write+0x84/0xa0 fs/read_write.c:652
> x64_sys_call+0x271a/0x2ce0 arch/x86/include/generated/asm/syscalls_64.h:2
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x9c/0x130 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Freed by task 7332:
> kasan_save_stack mm/kasan/common.c:47 [inline]
> kasan_save_track+0x30/0x70 mm/kasan/common.c:68
> kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579
> poison_slab_object+0x11a/0x190 mm/kasan/common.c:240
> __kasan_slab_free+0x3b/0x60 mm/kasan/common.c:256
> kasan_slab_free include/linux/kasan.h:184 [inline]
> slab_free_hook mm/slub.c:2106 [inline]
> slab_free mm/slub.c:4280 [inline]
> kfree+0x13c/0x330 mm/slub.c:4390
> msft_unregister+0x9d/0x120 net/bluetooth/msft.c:785
> hci_unregister_dev+0x1d9/0x520 net/bluetooth/hci_core.c:2771
> vhci_release+0x8c/0xe0 drivers/bluetooth/hci_vhci.c:674
> __fput+0x36f/0x750 fs/file_table.c:422
> ____fput+0x1e/0x30 fs/file_table.c:450
> task_work_run+0x1da/0x280 kernel/task_work.c:180
> exit_task_work include/linux/task_work.h:38 [inline]
> do_exit+0x856/0x2210 kernel/exit.c:878
> do_group_exit+0x201/0x2c0 kernel/exit.c:1027
> get_signal+0x12ff/0x1380 kernel/signal.c:2911
> arch_do_signal_or_restart+0x3b/0x650 arch/x86/kernel/signal.c:310
> exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
> exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
> syscall_exit_to_user_mode+0xcc/0x2a0 kernel/entry/common.c:218
> do_syscall_64+0xa8/0x130 arch/x86/entry/common.c:89
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> The buggy address belongs to the object at ffff888106cbbc00
> which belongs to the cache kmalloc-256 of size 256
> The buggy address is located 168 bytes inside of
> freed 256-byte region [ffff888106cbbc00, ffff888106cbbd00)
>
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106cba
> head: order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> flags: 0x17ffffe0000840(slab|head|node=0|zone=2|lastcpupid=0x3fffff)
> page_type: 0xffffffff()
> raw: 0017ffffe0000840 ffff888100042040 ffffea00042de590 ffffea00041b3e10
> raw: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000
> head: 0017ffffe0000840 ffff888100042040 ffffea00042de590 ffffea00041b3e10
> head: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000
> head: 0017ffffe0000001 ffffea00041b2e81 dead000000000122 00000000ffffffff
> head: 0000000200000000 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff888106cbbb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff888106cbbc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff888106cbbc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff888106cbbd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff888106cbbd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
> Fixes: 9e14606d8f38 ("Bluetooth: disable advertisement filters during suspend")
> Signed-off-by: Sungwoo Kim <iam@...g-woo.kim>
> ---
> v2: Move BT_DBG after null checking in msft_data_hold_unless_zero()
>
> net/bluetooth/msft.c | 124 ++++++++++++++++++++++++++++++++++---------
> 1 file changed, 99 insertions(+), 25 deletions(-)
>
> diff --git a/net/bluetooth/msft.c b/net/bluetooth/msft.c
> index 9612c5d1b..1f79e7980 100644
> --- a/net/bluetooth/msft.c
> +++ b/net/bluetooth/msft.c
> @@ -132,10 +132,45 @@ struct msft_data {
> __u8 filter_enabled;
> /* To synchronize add/remove address filter and monitor device event.*/
> struct mutex filter_lock;
> + struct kref kref;
NAK, the lifetime of this object should be tied to hdev which already
has a kref.
> };
>
> +static void msft_data_free(struct kref *kref);
> +
> +static struct msft_data *msft_data_hold_unless_zero(struct msft_data *msft)
> +{
> + if (!msft)
> + return NULL;
> +
> + BT_DBG("msft %p orig refcnt %u", msft, kref_read(&msft->kref));
> +
> + if (!kref_get_unless_zero(&msft->kref))
> + return NULL;
> +
> + return msft;
> +}
> +
> +static void msft_data_put(struct msft_data *msft)
> +{
> + BT_DBG("msft %p orig refcnt %u", msft, kref_read(&msft->kref));
> +
> + kref_put(&msft->kref, msft_data_free);
> +}
> +
> +static void msft_data_free(struct kref *kref)
> +{
> + struct msft_data *msft = container_of(kref, struct msft_data, kref);
> +
> + BT_DBG("msft %p", msft);
> +
> + kfree(msft->evt_prefix);
> + mutex_destroy(&msft->filter_lock);
> + kfree(msft);
> +}
> +
> bool msft_monitor_supported(struct hci_dev *hdev)
> {
> + /* msft_get_features() holds and put hdev->msft_data */
> return !!(msft_get_features(hdev) & MSFT_FEATURE_MASK_LE_ADV_MONITOR);
> }
>
> @@ -449,12 +484,17 @@ static int msft_remove_monitor_sync(struct hci_dev *hdev,
> /* This function requires the caller holds hci_req_sync_lock */
> int msft_suspend_sync(struct hci_dev *hdev)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> struct adv_monitor *monitor;
> int handle = 0;
>
> - if (!msft || !msft_monitor_supported(hdev))
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> + if (!msft)
> return 0;
> + if (!msft_monitor_supported(hdev)) {
> + msft_data_put(msft);
> + return 0;
> + }
>
> msft->suspending = true;
>
> @@ -471,6 +511,7 @@ int msft_suspend_sync(struct hci_dev *hdev)
> /* All monitors have been removed */
> msft->suspending = false;
>
> + msft_data_put(msft);
> return 0;
> }
>
> @@ -608,11 +649,17 @@ static void reregister_monitor(struct hci_dev *hdev)
> /* This function requires the caller holds hci_req_sync_lock */
> int msft_resume_sync(struct hci_dev *hdev)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
>
> - if (!msft || !msft_monitor_supported(hdev))
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> + if (!msft)
> return 0;
>
> + if (!msft_monitor_supported(hdev)) {
> + msft_data_put(msft);
> + return 0;
> + }
> +
> hci_dev_lock(hdev);
>
> /* Clear already tracked devices on resume. Once the monitors are
> @@ -625,17 +672,19 @@ int msft_resume_sync(struct hci_dev *hdev)
>
> reregister_monitor(hdev);
>
> + msft_data_put(msft);
> return 0;
> }
>
> /* This function requires the caller holds hci_req_sync_lock */
> void msft_do_open(struct hci_dev *hdev)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
>
> if (hdev->msft_opcode == HCI_OP_NOP)
> return;
>
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> if (!msft) {
> bt_dev_err(hdev, "MSFT extension not registered");
> return;
> @@ -650,8 +699,7 @@ void msft_do_open(struct hci_dev *hdev)
> msft->features = 0;
>
> if (!read_supported_features(hdev, msft)) {
> - hdev->msft_data = NULL;
> - kfree(msft);
> + msft_data_put(msft);
> return;
> }
>
> @@ -663,15 +711,17 @@ void msft_do_open(struct hci_dev *hdev)
> */
> reregister_monitor(hdev);
> }
> + msft_data_put(msft);
> }
>
> void msft_do_close(struct hci_dev *hdev)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> struct msft_monitor_advertisement_handle_data *handle_data, *tmp;
> struct msft_monitor_addr_filter_data *address_filter, *n;
> struct adv_monitor *monitor;
>
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> if (!msft)
> return;
>
> @@ -705,6 +755,8 @@ void msft_do_close(struct hci_dev *hdev)
> hdev->advmon_pend_notify = false;
> msft_monitor_device_del(hdev, 0, NULL, 0, true);
>
> + msft_data_put(msft);
> +
> hci_dev_unlock(hdev);
> }
>
> @@ -767,6 +819,7 @@ void msft_register(struct hci_dev *hdev)
> INIT_LIST_HEAD(&msft->address_filters);
> hdev->msft_data = msft;
> mutex_init(&msft->filter_lock);
> + kref_init(&msft->kref);
> }
>
> void msft_unregister(struct hci_dev *hdev)
> @@ -779,10 +832,7 @@ void msft_unregister(struct hci_dev *hdev)
> bt_dev_dbg(hdev, "Unregister MSFT extension");
>
> hdev->msft_data = NULL;
> -
> - kfree(msft->evt_prefix);
> - mutex_destroy(&msft->filter_lock);
> - kfree(msft);
> + msft_data_put(msft);
> }
>
> /* This function requires the caller holds hdev->lock */
> @@ -1068,10 +1118,11 @@ static void msft_monitor_device_evt(struct hci_dev *hdev, struct sk_buff *skb)
>
> void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *skb)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> u8 *evt_prefix;
> u8 *evt;
>
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> if (!msft)
> return;
>
> @@ -1081,21 +1132,21 @@ void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *skb)
> if (msft->evt_prefix_len > 0) {
> evt_prefix = msft_skb_pull(hdev, skb, 0, msft->evt_prefix_len);
> if (!evt_prefix)
> - return;
> + goto done;
>
> if (memcmp(evt_prefix, msft->evt_prefix, msft->evt_prefix_len))
> - return;
> + goto done;
> }
>
> /* Every event starts at least with an event code and the rest of
> * the data is variable and depends on the event code.
> */
> if (skb->len < 1)
> - return;
> + goto done;
>
> evt = msft_skb_pull(hdev, skb, 0, sizeof(*evt));
> if (!evt)
> - return;
> + goto done;
>
> hci_dev_lock(hdev);
>
> @@ -1112,13 +1163,24 @@ void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *skb)
> }
>
> hci_dev_unlock(hdev);
> +
> +done:
> + msft_data_put(msft);
> }
>
> __u64 msft_get_features(struct hci_dev *hdev)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> + unsigned long long features;
> +
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> + if (!msft)
> + return 0;
> +
> + features = msft->features;
>
> - return msft ? msft->features : 0;
> + msft_data_put(msft);
> + return features;
> }
>
> static void msft_le_set_advertisement_filter_enable_cb(struct hci_dev *hdev,
> @@ -1152,37 +1214,48 @@ static void msft_le_set_advertisement_filter_enable_cb(struct hci_dev *hdev,
> /* This function requires the caller holds hci_req_sync_lock */
> int msft_add_monitor_pattern(struct hci_dev *hdev, struct adv_monitor *monitor)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> + int err;
>
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> if (!msft)
> return -EOPNOTSUPP;
>
> - if (msft->resuming || msft->suspending)
> + if (msft->resuming || msft->suspending) {
> + msft_data_put(msft);
> return -EBUSY;
> + }
>
> - return msft_add_monitor_sync(hdev, monitor);
> + err = msft_add_monitor_sync(hdev, monitor);
> + msft_data_put(msft);
> + return err;
> }
>
> /* This function requires the caller holds hci_req_sync_lock */
> int msft_remove_monitor(struct hci_dev *hdev, struct adv_monitor *monitor)
> {
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> + int err;
>
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> if (!msft)
> return -EOPNOTSUPP;
>
> if (msft->resuming || msft->suspending)
> return -EBUSY;
>
> - return msft_remove_monitor_sync(hdev, monitor);
> + err = msft_remove_monitor_sync(hdev, monitor);
> + msft_data_put(msft);
> + return err;
> }
>
> int msft_set_filter_enable(struct hci_dev *hdev, bool enable)
> {
> struct msft_cp_le_set_advertisement_filter_enable cp;
> - struct msft_data *msft = hdev->msft_data;
> + struct msft_data *msft;
> int err;
>
> + msft = msft_data_hold_unless_zero(hdev->msft_data);
> if (!msft)
> return -EOPNOTSUPP;
>
> @@ -1193,6 +1266,7 @@ int msft_set_filter_enable(struct hci_dev *hdev, bool enable)
>
> msft_le_set_advertisement_filter_enable_cb(hdev, &cp, err);
>
> + msft_data_put(msft);
> return 0;
> }
>
> --
> 2.34.1
Looks at the current code I do wonder if the order is incorrect since we do:
msft_unregister(hdev);
hci_dev_do_close(hdev);
Anyway msft_unregister shall probably be renamed to msft_release and
then called from hci_release_dev instead since that is where we free
fields of hdev, not on unregister.
--
Luiz Augusto von Dentz
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