[PATCH v6] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd

[PATCH v6] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd

[Luiz Augusto von Dentz]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

After the hci sync command releases l2cap_conn, the hci receive data work
queue references the released l2cap_conn when sending to the upper layer.
Add hci dev lock to the hci receive data work queue to synchronize the two.

[1]
BUG: KASAN: slab-use-after-free in l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
Read of size 8 at addr ffff8880271a4000 by task kworker/u9:2/5837

CPU: 0 UID: 0 PID: 5837 Comm: kworker/u9:2 Not tainted 6.13.0-rc5-syzkaller-00163-gab75170520d4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: hci1 hci_rx_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 l2cap_build_cmd net/bluetooth/l2cap_core.c:2964 [inline]
 l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
 l2cap_sig_send_rej net/bluetooth/l2cap_core.c:5502 [inline]
 l2cap_sig_channel net/bluetooth/l2cap_core.c:5538 [inline]
 l2cap_recv_frame+0x221f/0x10db0 net/bluetooth/l2cap_core.c:6817
 hci_acldata_packet net/bluetooth/hci_core.c:3797 [inline]
 hci_rx_work+0x508/0xdb0 net/bluetooth/hci_core.c:4040
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 5837:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4329
 kmalloc_noprof include/linux/slab.h:901 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 l2cap_conn_add+0xa9/0x8e0 net/bluetooth/l2cap_core.c:6860
 l2cap_connect_cfm+0x115/0x1090 net/bluetooth/l2cap_core.c:7239
 hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline]
 hci_remote_features_evt+0x68e/0xac0 net/bluetooth/hci_event.c:3726
 hci_event_func net/bluetooth/hci_event.c:7473 [inline]
 hci_event_packet+0xac2/0x1540 net/bluetooth/hci_event.c:7525
 hci_rx_work+0x3f3/0xdb0 net/bluetooth/hci_core.c:4035
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 54:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2353 [inline]
 slab_free mm/slub.c:4613 [inline]
 kfree+0x196/0x430 mm/slub.c:4761
 l2cap_connect_cfm+0xcc/0x1090 net/bluetooth/l2cap_core.c:7235
 hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline]
 hci_conn_failed+0x287/0x400 net/bluetooth/hci_conn.c:1266
 hci_abort_conn_sync+0x56c/0x11f0 net/bluetooth/hci_sync.c:5603
 hci_cmd_sync_work+0x22b/0x400 net/bluetooth/hci_sync.c:332
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Reported-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=31c2f641b850a348a734
Tested-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/l2cap_core.c | 39 +++++++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 27b4c4a2ba1f..adb8c33ac595 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -948,6 +948,16 @@ static u8 l2cap_get_ident(struct l2cap_conn *conn)
 	return id;
 }
 
+static void l2cap_send_acl(struct l2cap_conn *conn, struct sk_buff *skb,
+			   u8 flags)
+{
+	/* Check if the hcon still valid before attempting to send */
+	if (hci_conn_valid(conn->hcon->hdev, conn->hcon))
+		hci_send_acl(conn->hchan, skb, flags);
+	else
+		kfree_skb(skb);
+}
+
 static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
 			   void *data)
 {
@@ -970,7 +980,7 @@ static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
 	bt_cb(skb)->force_active = BT_POWER_FORCE_ACTIVE_ON;
 	skb->priority = HCI_PRIO_MAX;
 
-	hci_send_acl(conn->hchan, skb, flags);
+	l2cap_send_acl(conn, skb, flags);
 }
 
 static void l2cap_do_send(struct l2cap_chan *chan, struct sk_buff *skb)
@@ -1792,13 +1802,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
 	mutex_unlock(&conn->chan_lock);
 
-	hci_chan_del(conn->hchan);
-
 	if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
 		cancel_delayed_work_sync(&conn->info_timer);
 
 	hcon->l2cap_data = NULL;
-	conn->hchan = NULL;
 	l2cap_conn_put(conn);
 }
 
@@ -1806,6 +1813,7 @@ static void l2cap_conn_free(struct kref *ref)
 {
 	struct l2cap_conn *conn = container_of(ref, struct l2cap_conn, ref);
 
+	hci_chan_del(conn->hchan);
 	hci_conn_put(conn->hcon);
 	kfree(conn);
 }
@@ -7466,14 +7474,33 @@ static void l2cap_recv_reset(struct l2cap_conn *conn)
 	conn->rx_len = 0;
 }
 
+static struct l2cap_conn *l2cap_conn_hold_unless_zero(struct l2cap_conn *c)
+{
+	BT_DBG("conn %p orig refcnt %u", c, kref_read(&c->ref));
+
+	if (!kref_get_unless_zero(&c->ref))
+		return NULL;
+
+	return c;
+}
+
 void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 {
-	struct l2cap_conn *conn = hcon->l2cap_data;
+	struct l2cap_conn *conn;
 	int len;
 
+	/* Lock hdev to access l2cap_data to avoid race with l2cap_conn_del */
+	hci_dev_lock(hcon->hdev);
+
+	conn = hcon->l2cap_data;
+
 	if (!conn)
 		conn = l2cap_conn_add(hcon);
 
+	conn = l2cap_conn_hold_unless_zero(conn);
+
+	hci_dev_unlock(hcon->hdev);
+
 	if (!conn)
 		goto drop;
 
@@ -7565,6 +7592,8 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 		break;
 	}
 
+	l2cap_conn_put(conn);
+
 drop:
 	kfree_skb(skb);
 }
-- 
2.48.1

RE: [v6] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2028 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=927650

---Test result---

Test Summary:
CheckPatch                    PENDING   0.29 seconds
GitLint                       PENDING   0.27 seconds
SubjectPrefix                 PASS      0.09 seconds
BuildKernel                   PASS      24.38 seconds
CheckAllWarning               PASS      26.83 seconds
CheckSparse                   PASS      30.63 seconds
BuildKernel32                 PASS      23.57 seconds
TestRunnerSetup               PASS      424.22 seconds
TestRunner_l2cap-tester       PASS      20.19 seconds
TestRunner_iso-tester         PASS      27.28 seconds
TestRunner_bnep-tester        PASS      8.33 seconds
TestRunner_mgmt-tester        FAIL      117.66 seconds
TestRunner_rfcomm-tester      PASS      7.61 seconds
TestRunner_sco-tester         PASS      9.66 seconds
TestRunner_ioctl-tester       PASS      8.16 seconds
TestRunner_mesh-tester        PASS      5.92 seconds
TestRunner_smp-tester         PASS      6.99 seconds
TestRunner_userchan-tester    PASS      5.05 seconds
IncrementalBuild              PENDING   0.46 seconds

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

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

##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 490, Passed: 484 (98.8%), Failed: 2, Not Run: 4

Failed Test Cases
LL Privacy - Set Flags 3 (2 Devices to RL)           Failed       0.170 seconds
LL Privacy - Start Discovery 2 (Disable RL)          Failed       0.184 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH v6] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd

[patchwork-bot+bluetooth]

Hello:

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

On Wed, 22 Jan 2025 16:25:14 -0500 you wrote:
> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> 
> After the hci sync command releases l2cap_conn, the hci receive data work
> queue references the released l2cap_conn when sending to the upper layer.
> Add hci dev lock to the hci receive data work queue to synchronize the two.
> 
> [1]
> BUG: KASAN: slab-use-after-free in l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
> Read of size 8 at addr ffff8880271a4000 by task kworker/u9:2/5837
> 
> [...]

Here is the summary with links:
  - [v6] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd
    https://git.kernel.org/bluetooth/bluetooth-next/c/6ab54a717189

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH v6] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd

[Hillf Danton]

On Wed, 22 Jan 2025 16:25:14 -0500
> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> 
> After the hci sync command releases l2cap_conn, the hci receive data work
> queue references the released l2cap_conn when sending to the upper layer.
> Add hci dev lock to the hci receive data work queue to synchronize the two.
> 
> [1]
> BUG: KASAN: slab-use-after-free in l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
> Read of size 8 at addr ffff8880271a4000 by task kworker/u9:2/5837
> 
> CPU: 0 UID: 0 PID: 5837 Comm: kworker/u9:2 Not tainted 6.13.0-rc5-syzkaller-00163-gab75170520d4 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Workqueue: hci1 hci_rx_work
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:378 [inline]
>  print_report+0x169/0x550 mm/kasan/report.c:489
>  kasan_report+0x143/0x180 mm/kasan/report.c:602
>  l2cap_build_cmd net/bluetooth/l2cap_core.c:2964 [inline]
>  l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954
>  l2cap_sig_send_rej net/bluetooth/l2cap_core.c:5502 [inline]
>  l2cap_sig_channel net/bluetooth/l2cap_core.c:5538 [inline]
>  l2cap_recv_frame+0x221f/0x10db0 net/bluetooth/l2cap_core.c:6817
>  hci_acldata_packet net/bluetooth/hci_core.c:3797 [inline]
>  hci_rx_work+0x508/0xdb0 net/bluetooth/hci_core.c:4040
>  process_one_work kernel/workqueue.c:3229 [inline]
>  process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
>  worker_thread+0x870/0xd30 kernel/workqueue.c:3391
>  kthread+0x2f0/0x390 kernel/kthread.c:389
>  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>  </TASK>
> 
> Allocated by task 5837:
>  kasan_save_stack mm/kasan/common.c:47 [inline]
>  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
>  __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
>  kasan_kmalloc include/linux/kasan.h:260 [inline]
>  __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4329
>  kmalloc_noprof include/linux/slab.h:901 [inline]
>  kzalloc_noprof include/linux/slab.h:1037 [inline]
>  l2cap_conn_add+0xa9/0x8e0 net/bluetooth/l2cap_core.c:6860
>  l2cap_connect_cfm+0x115/0x1090 net/bluetooth/l2cap_core.c:7239
>  hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline]
>  hci_remote_features_evt+0x68e/0xac0 net/bluetooth/hci_event.c:3726
>  hci_event_func net/bluetooth/hci_event.c:7473 [inline]
>  hci_event_packet+0xac2/0x1540 net/bluetooth/hci_event.c:7525
>  hci_rx_work+0x3f3/0xdb0 net/bluetooth/hci_core.c:4035
>  process_one_work kernel/workqueue.c:3229 [inline]
>  process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
>  worker_thread+0x870/0xd30 kernel/workqueue.c:3391
>  kthread+0x2f0/0x390 kernel/kthread.c:389
>  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> 
> Freed by task 54:
>  kasan_save_stack mm/kasan/common.c:47 [inline]
>  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
>  kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582
>  poison_slab_object mm/kasan/common.c:247 [inline]
>  __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
>  kasan_slab_free include/linux/kasan.h:233 [inline]
>  slab_free_hook mm/slub.c:2353 [inline]
>  slab_free mm/slub.c:4613 [inline]
>  kfree+0x196/0x430 mm/slub.c:4761
>  l2cap_connect_cfm+0xcc/0x1090 net/bluetooth/l2cap_core.c:7235
>  hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline]
>  hci_conn_failed+0x287/0x400 net/bluetooth/hci_conn.c:1266
>  hci_abort_conn_sync+0x56c/0x11f0 net/bluetooth/hci_sync.c:5603
>  hci_cmd_sync_work+0x22b/0x400 net/bluetooth/hci_sync.c:332
>  process_one_work kernel/workqueue.c:3229 [inline]
>  process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
>  worker_thread+0x870/0xd30 kernel/workqueue.c:3391
>  kthread+0x2f0/0x390 kernel/kthread.c:389
>  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> 
> Reported-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=31c2f641b850a348a734
> Tested-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> ---

Given V6, feel free to add change log as a maintainer Luiz.

>  net/bluetooth/l2cap_core.c | 39 +++++++++++++++++++++++++++++++++-----
>  1 file changed, 34 insertions(+), 5 deletions(-)
> 
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 27b4c4a2ba1f..adb8c33ac595 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -948,6 +948,16 @@ static u8 l2cap_get_ident(struct l2cap_conn *conn)
>  	return id;
>  }
>  
> +static void l2cap_send_acl(struct l2cap_conn *conn, struct sk_buff *skb,
> +			   u8 flags)
> +{
> +	/* Check if the hcon still valid before attempting to send */
> +	if (hci_conn_valid(conn->hcon->hdev, conn->hcon))

Checking validity makes no sense because nothing prevents hcon from
becoming invalid after check.

PS spin with linux-kernel@vger.kernel.org, netdev@vger.kernel.org cced.

> +		hci_send_acl(conn->hchan, skb, flags);
> +	else
> +		kfree_skb(skb);
> +}
> +
>  static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
>  			   void *data)
>  {
> @@ -970,7 +980,7 @@ static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
>  	bt_cb(skb)->force_active = BT_POWER_FORCE_ACTIVE_ON;
>  	skb->priority = HCI_PRIO_MAX;
>  
> -	hci_send_acl(conn->hchan, skb, flags);
> +	l2cap_send_acl(conn, skb, flags);
>  }
>  
>  static void l2cap_do_send(struct l2cap_chan *chan, struct sk_buff *skb)
> @@ -1792,13 +1802,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
>  
>  	mutex_unlock(&conn->chan_lock);
>  
> -	hci_chan_del(conn->hchan);
> -
>  	if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT)
>  		cancel_delayed_work_sync(&conn->info_timer);
>  
>  	hcon->l2cap_data = NULL;
> -	conn->hchan = NULL;
>  	l2cap_conn_put(conn);
>  }
>  
> @@ -1806,6 +1813,7 @@ static void l2cap_conn_free(struct kref *ref)
>  {
>  	struct l2cap_conn *conn = container_of(ref, struct l2cap_conn, ref);
>  
> +	hci_chan_del(conn->hchan);
>  	hci_conn_put(conn->hcon);
>  	kfree(conn);
>  }
> @@ -7466,14 +7474,33 @@ static void l2cap_recv_reset(struct l2cap_conn *conn)
>  	conn->rx_len = 0;
>  }
>  
> +static struct l2cap_conn *l2cap_conn_hold_unless_zero(struct l2cap_conn *c)
> +{
> +	BT_DBG("conn %p orig refcnt %u", c, kref_read(&c->ref));
> +
> +	if (!kref_get_unless_zero(&c->ref))
> +		return NULL;
> +
> +	return c;
> +}
> +
>  void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
>  {
> -	struct l2cap_conn *conn = hcon->l2cap_data;
> +	struct l2cap_conn *conn;
>  	int len;
>  
> +	/* Lock hdev to access l2cap_data to avoid race with l2cap_conn_del */
> +	hci_dev_lock(hcon->hdev);
> +
> +	conn = hcon->l2cap_data;
> +
>  	if (!conn)
>  		conn = l2cap_conn_add(hcon);
>  
> +	conn = l2cap_conn_hold_unless_zero(conn);
> +
> +	hci_dev_unlock(hcon->hdev);
> +
>  	if (!conn)
>  		goto drop;
>  
> @@ -7565,6 +7592,8 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
>  		break;
>  	}
>  
> +	l2cap_conn_put(conn);
> +
>  drop:
>  	kfree_skb(skb);
>  }
> -- 
> 2.48.1