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Bluetooth: use RCU for hci_conn_params and iterate safely in hci_sync
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hci_update_accept_list_sync iterates over hdev->pend_le_conns and
hdev->pend_le_reports, and waits for controller events in the loop body,
without holding hdev lock.

Meanwhile, these lists and the items may be modified e.g. by
le_scan_cleanup. This can invalidate the list cursor or any other item
in the list, resulting to invalid behavior (eg use-after-free).

Use RCU for the hci_conn_params action lists. Since the loop bodies in
hci_sync block and we cannot use RCU or hdev->lock for the whole loop,
copy list items first and then iterate on the copy. Only the flags field
is written from elsewhere, so READ_ONCE/WRITE_ONCE should guarantee we
read valid values.

Free params everywhere with hci_conn_params_free so the cleanup is
guaranteed to be done properly.

This fixes the following, which can be triggered e.g. by BlueZ new
mgmt-tester case "Add + Remove Device Nowait - Success", or by changing
hci_le_set_cig_params to always return false, and running iso-tester:

==================================================================
BUG: KASAN: slab-use-after-free in hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841)
Read of size 8 at addr ffff888001265018 by task kworker/u3:0/32

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
<TASK>
dump_stack_lvl (./arch/x86/include/asm/irqflags.h:134 lib/dump_stack.c:107)
print_report (mm/kasan/report.c:320 mm/kasan/report.c:430)
? __virt_addr_valid (./include/linux/mmzone.h:1915 ./include/linux/mmzone.h:2011 arch/x86/mm/physaddr.c:65)
? hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841)
kasan_report (mm/kasan/report.c:538)
? hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841)
hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2536 net/bluetooth/hci_sync.c:2723 net/bluetooth/hci_sync.c:2841)
? __pfx_hci_update_passive_scan_sync (net/bluetooth/hci_sync.c:2780)
? mutex_lock (kernel/locking/mutex.c:282)
? __pfx_mutex_lock (kernel/locking/mutex.c:282)
? __pfx_mutex_unlock (kernel/locking/mutex.c:538)
? __pfx_update_passive_scan_sync (net/bluetooth/hci_sync.c:2861)
hci_cmd_sync_work (net/bluetooth/hci_sync.c:306)
process_one_work (./arch/x86/include/asm/preempt.h:27 kernel/workqueue.c:2399)
worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2538)
? __pfx_worker_thread (kernel/workqueue.c:2480)
kthread (kernel/kthread.c:376)
? __pfx_kthread (kernel/kthread.c:331)
ret_from_fork (arch/x86/entry/entry_64.S:314)
</TASK>

Allocated by task 31:
kasan_save_stack (mm/kasan/common.c:46)
kasan_set_track (mm/kasan/common.c:52)
__kasan_kmalloc (mm/kasan/common.c:374 mm/kasan/common.c:383)
hci_conn_params_add (./include/linux/slab.h:580 ./include/linux/slab.h:720 net/bluetooth/hci_core.c:2277)
hci_connect_le_scan (net/bluetooth/hci_conn.c:1419 net/bluetooth/hci_conn.c:1589)
hci_connect_cis (net/bluetooth/hci_conn.c:2266)
iso_connect_cis (net/bluetooth/iso.c:390)
iso_sock_connect (net/bluetooth/iso.c:899)
__sys_connect (net/socket.c:2003 net/socket.c:2020)
__x64_sys_connect (net/socket.c:2027)
do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)

Freed by task 15:
kasan_save_stack (mm/kasan/common.c:46)
kasan_set_track (mm/kasan/common.c:52)
kasan_save_free_info (mm/kasan/generic.c:523)
__kasan_slab_free (mm/kasan/common.c:238 mm/kasan/common.c:200 mm/kasan/common.c:244)
__kmem_cache_free (mm/slub.c:1807 mm/slub.c:3787 mm/slub.c:3800)
hci_conn_params_del (net/bluetooth/hci_core.c:2323)
le_scan_cleanup (net/bluetooth/hci_conn.c:202)
process_one_work (./arch/x86/include/asm/preempt.h:27 kernel/workqueue.c:2399)
worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2538)
kthread (kernel/kthread.c:376)
ret_from_fork (arch/x86/entry/entry_64.S:314)
==================================================================

Fixes: e8907f7 ("Bluetooth: hci_sync: Make use of hci_cmd_sync_queue set 3")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
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@pv @Vudentz
pv authored and Vudentz committed Jul 6, 2023
1 parent 93051fb commit f8dfe15
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Showing 6 changed files with 164 additions and 44 deletions.
5 changes: 5 additions & 0 deletions include/net/bluetooth/hci_core.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -822,6 +822,7 @@ struct hci_conn_params {

struct hci_conn *conn;
bool explicit_connect;
/* Accessed without hdev->lock: */
hci_conn_flags_t flags;
u8 privacy_mode;
};
Expand Down Expand Up @@ -1605,7 +1606,11 @@ struct hci_conn_params *hci_conn_params_add(struct hci_dev *hdev,
bdaddr_t *addr, u8 addr_type);
void hci_conn_params_del(struct hci_dev *hdev, bdaddr_t *addr, u8 addr_type);
void hci_conn_params_clear_disabled(struct hci_dev *hdev);
void hci_conn_params_free(struct hci_conn_params *param);

void hci_pend_le_list_del_init(struct hci_conn_params *param);
void hci_pend_le_list_add(struct hci_conn_params *param,
struct list_head *list);
struct hci_conn_params *hci_pend_le_action_lookup(struct list_head *list,
bdaddr_t *addr,
u8 addr_type);
Expand Down
10 changes: 5 additions & 5 deletions net/bluetooth/hci_conn.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -118,7 +118,7 @@ static void hci_connect_le_scan_cleanup(struct hci_conn *conn, u8 status)
*/
params->explicit_connect = false;

list_del_init(&params->action);
hci_pend_le_list_del_init(params);

switch (params->auto_connect) {
case HCI_AUTO_CONN_EXPLICIT:
Expand All @@ -127,10 +127,10 @@ static void hci_connect_le_scan_cleanup(struct hci_conn *conn, u8 status)
return;
case HCI_AUTO_CONN_DIRECT:
case HCI_AUTO_CONN_ALWAYS:
list_add(&params->action, &hdev->pend_le_conns);
hci_pend_le_list_add(params, &hdev->pend_le_conns);
break;
case HCI_AUTO_CONN_REPORT:
list_add(&params->action, &hdev->pend_le_reports);
hci_pend_le_list_add(params, &hdev->pend_le_reports);
break;
default:
break;
Expand Down Expand Up @@ -1435,8 +1435,8 @@ static int hci_explicit_conn_params_set(struct hci_dev *hdev,
if (params->auto_connect == HCI_AUTO_CONN_DISABLED ||
params->auto_connect == HCI_AUTO_CONN_REPORT ||
params->auto_connect == HCI_AUTO_CONN_EXPLICIT) {
list_del_init(&params->action);
list_add(&params->action, &hdev->pend_le_conns);
hci_pend_le_list_del_init(params);
hci_pend_le_list_add(params, &hdev->pend_le_conns);
}

params->explicit_connect = true;
Expand Down
38 changes: 31 additions & 7 deletions net/bluetooth/hci_core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2249,21 +2249,45 @@ struct hci_conn_params *hci_conn_params_lookup(struct hci_dev *hdev,
return NULL;
}

/* This function requires the caller holds hdev->lock */
/* This function requires the caller holds hdev->lock or rcu_read_lock */
struct hci_conn_params *hci_pend_le_action_lookup(struct list_head *list,
bdaddr_t *addr, u8 addr_type)
{
struct hci_conn_params *param;

list_for_each_entry(param, list, action) {
rcu_read_lock();

list_for_each_entry_rcu(param, list, action) {
if (bacmp(&param->addr, addr) == 0 &&
param->addr_type == addr_type)
param->addr_type == addr_type) {
rcu_read_unlock();
return param;
}
}

rcu_read_unlock();

return NULL;
}

/* This function requires the caller holds hdev->lock */
void hci_pend_le_list_del_init(struct hci_conn_params *param)
{
if (list_empty(&param->action))
return;

list_del_rcu(&param->action);
synchronize_rcu();
INIT_LIST_HEAD(&param->action);
}

/* This function requires the caller holds hdev->lock */
void hci_pend_le_list_add(struct hci_conn_params *param,
struct list_head *list)
{
list_add_rcu(&param->action, list);
}

/* This function requires the caller holds hdev->lock */
struct hci_conn_params *hci_conn_params_add(struct hci_dev *hdev,
bdaddr_t *addr, u8 addr_type)
Expand Down Expand Up @@ -2297,14 +2321,15 @@ struct hci_conn_params *hci_conn_params_add(struct hci_dev *hdev,
return params;
}

static void hci_conn_params_free(struct hci_conn_params *params)
void hci_conn_params_free(struct hci_conn_params *params)
{
hci_pend_le_list_del_init(params);

if (params->conn) {
hci_conn_drop(params->conn);
hci_conn_put(params->conn);
}

list_del(&params->action);
list_del(&params->list);
kfree(params);
}
Expand Down Expand Up @@ -2342,8 +2367,7 @@ void hci_conn_params_clear_disabled(struct hci_dev *hdev)
continue;
}

list_del(&params->list);
kfree(params);
hci_conn_params_free(params);
}

BT_DBG("All LE disabled connection parameters were removed");
Expand Down
12 changes: 6 additions & 6 deletions net/bluetooth/hci_event.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1564,7 +1564,7 @@ static u8 hci_cc_le_set_privacy_mode(struct hci_dev *hdev, void *data,

params = hci_conn_params_lookup(hdev, &cp->bdaddr, cp->bdaddr_type);
if (params)
params->privacy_mode = cp->mode;
WRITE_ONCE(params->privacy_mode, cp->mode);

hci_dev_unlock(hdev);

Expand Down Expand Up @@ -2804,8 +2804,8 @@ static void hci_cs_disconnect(struct hci_dev *hdev, u8 status)

case HCI_AUTO_CONN_DIRECT:
case HCI_AUTO_CONN_ALWAYS:
list_del_init(&params->action);
list_add(&params->action, &hdev->pend_le_conns);
hci_pend_le_list_del_init(params);
hci_pend_le_list_add(params, &hdev->pend_le_conns);
break;

default:
Expand Down Expand Up @@ -3423,8 +3423,8 @@ static void hci_disconn_complete_evt(struct hci_dev *hdev, void *data,

case HCI_AUTO_CONN_DIRECT:
case HCI_AUTO_CONN_ALWAYS:
list_del_init(&params->action);
list_add(&params->action, &hdev->pend_le_conns);
hci_pend_le_list_del_init(params);
hci_pend_le_list_add(params, &hdev->pend_le_conns);
hci_update_passive_scan(hdev);
break;

Expand Down Expand Up @@ -5972,7 +5972,7 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
params = hci_pend_le_action_lookup(&hdev->pend_le_conns, &conn->dst,
conn->dst_type);
if (params) {
list_del_init(&params->action);
hci_pend_le_list_del_init(params);
if (params->conn) {
hci_conn_drop(params->conn);
hci_conn_put(params->conn);
Expand Down
117 changes: 106 additions & 11 deletions net/bluetooth/hci_sync.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2160,15 +2160,23 @@ static int hci_le_del_accept_list_sync(struct hci_dev *hdev,
return 0;
}

struct conn_params {
bdaddr_t addr;
u8 addr_type;
hci_conn_flags_t flags;
u8 privacy_mode;
};

/* Adds connection to resolve list if needed.
* Setting params to NULL programs local hdev->irk
*/
static int hci_le_add_resolve_list_sync(struct hci_dev *hdev,
struct hci_conn_params *params)
struct conn_params *params)
{
struct hci_cp_le_add_to_resolv_list cp;
struct smp_irk *irk;
struct bdaddr_list_with_irk *entry;
struct hci_conn_params *p;

if (!use_ll_privacy(hdev))
return 0;
Expand Down Expand Up @@ -2203,6 +2211,16 @@ static int hci_le_add_resolve_list_sync(struct hci_dev *hdev,
/* Default privacy mode is always Network */
params->privacy_mode = HCI_NETWORK_PRIVACY;

rcu_read_lock();
p = hci_pend_le_action_lookup(&hdev->pend_le_conns,
&params->addr, params->addr_type);
if (!p)
p = hci_pend_le_action_lookup(&hdev->pend_le_reports,
&params->addr, params->addr_type);
if (p)
WRITE_ONCE(p->privacy_mode, HCI_NETWORK_PRIVACY);
rcu_read_unlock();

done:
if (hci_dev_test_flag(hdev, HCI_PRIVACY))
memcpy(cp.local_irk, hdev->irk, 16);
Expand All @@ -2215,7 +2233,7 @@ static int hci_le_add_resolve_list_sync(struct hci_dev *hdev,

/* Set Device Privacy Mode. */
static int hci_le_set_privacy_mode_sync(struct hci_dev *hdev,
struct hci_conn_params *params)
struct conn_params *params)
{
struct hci_cp_le_set_privacy_mode cp;
struct smp_irk *irk;
Expand All @@ -2240,6 +2258,8 @@ static int hci_le_set_privacy_mode_sync(struct hci_dev *hdev,
bacpy(&cp.bdaddr, &irk->bdaddr);
cp.mode = HCI_DEVICE_PRIVACY;

/* Note: params->privacy_mode is not updated since it is a copy */

return __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_PRIVACY_MODE,
sizeof(cp), &cp, HCI_CMD_TIMEOUT);
}
Expand All @@ -2249,7 +2269,7 @@ static int hci_le_set_privacy_mode_sync(struct hci_dev *hdev,
* properly set the privacy mode.
*/
static int hci_le_add_accept_list_sync(struct hci_dev *hdev,
struct hci_conn_params *params,
struct conn_params *params,
u8 *num_entries)
{
struct hci_cp_le_add_to_accept_list cp;
Expand Down Expand Up @@ -2447,6 +2467,52 @@ struct sk_buff *hci_read_local_oob_data_sync(struct hci_dev *hdev,
return __hci_cmd_sync_sk(hdev, opcode, 0, NULL, 0, HCI_CMD_TIMEOUT, sk);
}

static struct conn_params *conn_params_copy(struct list_head *list, size_t *n)
{
struct hci_conn_params *params;
struct conn_params *p;
size_t i;

rcu_read_lock();

i = 0;
list_for_each_entry_rcu(params, list, action)
++i;
*n = i;

rcu_read_unlock();

p = kvcalloc(*n, sizeof(struct conn_params), GFP_KERNEL);
if (!p)
return NULL;

rcu_read_lock();

i = 0;
list_for_each_entry_rcu(params, list, action) {
/* Racing adds are handled in next scan update */
if (i >= *n)
break;

/* No hdev->lock, but: addr, addr_type are immutable.
* privacy_mode is only written by us or in
* hci_cc_le_set_privacy_mode that we wait for.
* We should be idempotent so MGMT updating flags
* while we are processing is OK.
*/
bacpy(&p[i].addr, &params->addr);
p[i].addr_type = params->addr_type;
p[i].flags = READ_ONCE(params->flags);
p[i].privacy_mode = READ_ONCE(params->privacy_mode);
++i;
}

rcu_read_unlock();

*n = i;
return p;
}

/* Device must not be scanning when updating the accept list.
*
* Update is done using the following sequence:
Expand All @@ -2466,11 +2532,12 @@ struct sk_buff *hci_read_local_oob_data_sync(struct hci_dev *hdev,
*/
static u8 hci_update_accept_list_sync(struct hci_dev *hdev)
{
struct hci_conn_params *params;
struct conn_params *params;
struct bdaddr_list *b, *t;
u8 num_entries = 0;
bool pend_conn, pend_report;
u8 filter_policy;
size_t i, n;
int err;

/* Pause advertising if resolving list can be used as controllers
Expand Down Expand Up @@ -2504,6 +2571,7 @@ static u8 hci_update_accept_list_sync(struct hci_dev *hdev)
if (hci_conn_hash_lookup_le(hdev, &b->bdaddr, b->bdaddr_type))
continue;

/* Pointers not dereferenced, no locks needed */
pend_conn = hci_pend_le_action_lookup(&hdev->pend_le_conns,
&b->bdaddr,
b->bdaddr_type);
Expand Down Expand Up @@ -2532,23 +2600,50 @@ static u8 hci_update_accept_list_sync(struct hci_dev *hdev)
* available accept list entries in the controller, then
* just abort and return filer policy value to not use the
* accept list.
*
* The list and params may be mutated while we wait for events,
* so make a copy and iterate it.
*/
list_for_each_entry(params, &hdev->pend_le_conns, action) {
err = hci_le_add_accept_list_sync(hdev, params, &num_entries);
if (err)

params = conn_params_copy(&hdev->pend_le_conns, &n);
if (!params) {
err = -ENOMEM;
goto done;
}

for (i = 0; i < n; ++i) {
err = hci_le_add_accept_list_sync(hdev, &params[i],
&num_entries);
if (err) {
kvfree(params);
goto done;
}
}

kvfree(params);

/* After adding all new pending connections, walk through
* the list of pending reports and also add these to the
* accept list if there is still space. Abort if space runs out.
*/
list_for_each_entry(params, &hdev->pend_le_reports, action) {
err = hci_le_add_accept_list_sync(hdev, params, &num_entries);
if (err)

params = conn_params_copy(&hdev->pend_le_reports, &n);
if (!params) {
err = -ENOMEM;
goto done;
}

for (i = 0; i < n; ++i) {
err = hci_le_add_accept_list_sync(hdev, &params[i],
&num_entries);
if (err) {
kvfree(params);
goto done;
}
}

kvfree(params);

/* Use the allowlist unless the following conditions are all true:
* - We are not currently suspending
* - There are 1 or more ADV monitors registered and it's not offloaded
Expand Down Expand Up @@ -4837,12 +4932,12 @@ static void hci_pend_le_actions_clear(struct hci_dev *hdev)
struct hci_conn_params *p;

list_for_each_entry(p, &hdev->le_conn_params, list) {
hci_pend_le_list_del_init(p);
if (p->conn) {
hci_conn_drop(p->conn);
hci_conn_put(p->conn);
p->conn = NULL;
}
list_del_init(&p->action);
}

BT_DBG("All LE pending actions cleared");
Expand Down
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