[PATCH] Bluetooth: ISO: validate ISO_END fragments

[PATCH] Bluetooth: ISO: validate ISO_END fragments

[Kangzheng Gu]

A malformed ISO_END fragment can trigger a NULL pointer dereference
due to missing validation before processing. An oversized end fragment
should also be rejected.

Add the same validation for ISO_END as for ISO_CONT, and reset the
in-progress reassembly state when malformed input is detected.

Fixes: ccf74f2390d6 ("Bluetooth: Add BTPROTO_ISO socket type")
Cc: stable@vger.kernel.org
Signed-off-by: Kangzheng Gu <xiaoguai0992@gmail.com>
---
 net/bluetooth/iso.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index be145e2736b7..8707f3c4b103 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -2587,6 +2587,27 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags)
 		break;
 
 	case ISO_END:
+		BT_DBG("End: frag len %d (expecting %d)", skb->len,
+		       conn->rx_len);
+
+		if (!conn->rx_len) {
+			BT_ERR("Unexpected end frame (len %d)",
+			       skb->len);
+			kfree_skb(conn->rx_skb);
+			conn->rx_skb = NULL;
+			conn->rx_len = 0;
+			goto drop;
+		}
+
+		if (skb->len > conn->rx_len) {
+			BT_ERR("Fragment is too long (len %d, expected %d)",
+			       skb->len, conn->rx_len);
+			kfree_skb(conn->rx_skb);
+			conn->rx_skb = NULL;
+			conn->rx_len = 0;
+			goto drop;
+		}
+
 		skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
 					  skb->len);
 		conn->rx_len -= skb->len;
-- 
2.50.1

RE: Bluetooth: ISO: validate ISO_END fragments

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2913 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=1074052

---Test result---

Test Summary:
CheckPatch                    PENDING   0.25 seconds
GitLint                       PENDING   0.20 seconds
SubjectPrefix                 PASS      0.12 seconds
BuildKernel                   PASS      26.03 seconds
CheckAllWarning               PASS      28.36 seconds
CheckSparse                   PASS      27.30 seconds
BuildKernel32                 PASS      26.91 seconds
TestRunnerSetup               PASS      567.23 seconds
TestRunner_l2cap-tester       PASS      27.98 seconds
TestRunner_iso-tester         PASS      35.49 seconds
TestRunner_bnep-tester        PASS      6.46 seconds
TestRunner_mgmt-tester        FAIL      114.56 seconds
TestRunner_rfcomm-tester      PASS      9.50 seconds
TestRunner_sco-tester         FAIL      14.27 seconds
TestRunner_ioctl-tester       PASS      10.11 seconds
TestRunner_mesh-tester        FAIL      11.42 seconds
TestRunner_smp-tester         PASS      8.63 seconds
TestRunner_userchan-tester    PASS      6.69 seconds
IncrementalBuild              PENDING   0.53 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: 494, Passed: 485 (98.2%), Failed: 5, Not Run: 4

Failed Test Cases
Adv. connectable & connected (central) - Success     Failed       0.131 seconds
Adv. non-connectable & connected (central) - Success Failed       0.129 seconds
Ext Adv. connectable & connected (central)           Failed       0.180 seconds
Ext Adv. non-connectable & connected (central)       Failed       0.184 seconds
Read Exp Feature - Success                           Failed       0.115 seconds
##############################
Test: TestRunner_sco-tester - FAIL
Desc: Run sco-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
BUG: sleeping function called from invalid context at net/core/sock.c:3782
Total: 30, Passed: 30 (100.0%), Failed: 0, Not Run: 0
##############################
Test: TestRunner_mesh-tester - FAIL
Desc: Run mesh-tester with test-runner
Output:
Total: 10, Passed: 8 (80.0%), Failed: 2, Not Run: 0

Failed Test Cases
Mesh - Send cancel - 1                               Timed out    1.875 seconds
Mesh - Send cancel - 2                               Timed out    2.001 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH] Bluetooth: ISO: validate ISO_END fragments

[Luiz Augusto von Dentz]

Hi Kangzheng,

On Sat, Mar 28, 2026 at 4:09 PM Kangzheng Gu <xiaoguai0992@gmail.com> wrote:
>
> A malformed ISO_END fragment can trigger a NULL pointer dereference
> due to missing validation before processing. An oversized end fragment
> should also be rejected.
>
> Add the same validation for ISO_END as for ISO_CONT, and reset the
> in-progress reassembly state when malformed input is detected.
>
> Fixes: ccf74f2390d6 ("Bluetooth: Add BTPROTO_ISO socket type")
> Cc: stable@vger.kernel.org
> Signed-off-by: Kangzheng Gu <xiaoguai0992@gmail.com>
> ---
>  net/bluetooth/iso.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
> index be145e2736b7..8707f3c4b103 100644
> --- a/net/bluetooth/iso.c
> +++ b/net/bluetooth/iso.c
> @@ -2587,6 +2587,27 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags)
>                 break;
>
>         case ISO_END:
> +               BT_DBG("End: frag len %d (expecting %d)", skb->len,
> +                      conn->rx_len);
> +
> +               if (!conn->rx_len) {
> +                       BT_ERR("Unexpected end frame (len %d)",
> +                              skb->len);
> +                       kfree_skb(conn->rx_skb);
> +                       conn->rx_skb = NULL;
> +                       conn->rx_len = 0;
> +                       goto drop;
> +               }

I suspect this was not quite right:

https://sashiko.dev/#/patchset/20260328200938.140528-1-xiaoguai0992%40gmail.com

Have you actually validated this changes against any hardware?

> +               if (skb->len > conn->rx_len) {
> +                       BT_ERR("Fragment is too long (len %d, expected %d)",
> +                              skb->len, conn->rx_len);
> +                       kfree_skb(conn->rx_skb);
> +                       conn->rx_skb = NULL;
> +                       conn->rx_len = 0;
> +                       goto drop;
> +               }

Hmm, this is the end fragment so anything other than skb->len ==
conn->rx_len is unexpected.

>                 skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
>                                           skb->len);
>                 conn->rx_len -= skb->len;
> --
> 2.50.1
>


-- 
Luiz Augusto von Dentz

Re: [PATCH] Bluetooth: ISO: validate ISO_END fragments

[Nathan Rebello]

Hi,

I submitted a fix for this same issue earlier on March 28th [1], and
have since sent a v2 addressing Luiz's feedback on the end fragment
check [2].

[1] https://lore.kernel.org/linux-bluetooth/20260328035813.296410-1-nathan.c.rebello@gmail.com/
[2] https://lore.kernel.org/linux-bluetooth/20260330212129.319339-1-nathan.c.rebello@gmail.com/

Thanks,
Nathan Rebello

Re: [PATCH] Bluetooth: ISO: validate ISO_END fragments

[Luiz Augusto von Dentz]

Hi,

On Mon, Mar 30, 2026 at 5:59 PM Nathan Rebello
<nathan.c.rebello@gmail.com> wrote:
>
> Hi,
>
> I submitted a fix for this same issue earlier on March 28th [1], and
> have since sent a v2 addressing Luiz's feedback on the end fragment
> check [2].
>
> [1] https://lore.kernel.org/linux-bluetooth/20260328035813.296410-1-nathan.c.rebello@gmail.com/
> [2] https://lore.kernel.org/linux-bluetooth/20260330212129.319339-1-nathan.c.rebello@gmail.com/
>
> Thanks,
> Nathan Rebello

And both seem to have the same problem:

https://sashiko.dev/#/patchset/20260330212129.319339-1-nathan.c.rebello%40gmail.com



-- 
Luiz Augusto von Dentz

Re: [PATCH] Bluetooth: ISO: validate ISO_END fragments

[Nathan Rebello]

Hi Luiz,

Thanks for the feedback. I've sent a v3 addressing this -- checking
!conn->rx_skb instead of !conn->rx_len:

https://lore.kernel.org/linux-bluetooth/20260330221015.322337-1-nathan.c.rebello@gmail.com/

Nathan Rebello

Re: [PATCH] Bluetooth: ISO: validate ISO_END fragments

[Kangzheng Gu]

Hi,

Thanks for the feedback. I do not have access to actual hardware to
validate this.

I chose to use ‘>’ rather than ‘!=’ because of the subsequent code,
conn->rx_len -= skb->len.
This made me wonder why it is not simply conn->rx_len = 0.
My understanding is that there may be situations where an ISO_END
packet carries more data than expected, which we may not want to
reject outright.

Since I am not certain whether strictly enforcing conn->rx_len ==
skb->len could introduce compatibility issues with existing Bluetooth
firmware, I opted for a more defensive check using ‘>’ instead of
‘!=’.

If one can make sure such a strict check will not introduction any
regression, I would like to provide a updated version of this patch.

Best Regards,
Kangzheng Gu


>
> Hi Luiz,
>
> Thanks for the feedback. I've sent a v3 addressing this -- checking
> !conn->rx_skb instead of !conn->rx_len:
>
> https://lore.kernel.org/linux-bluetooth/20260330221015.322337-1-nathan.c.rebello@gmail.com/
>
> Nathan Rebello

RE: Bluetooth: ISO: validate ISO_END fragments

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 6877 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=1074052

---Test result---

Test Summary:
CheckPatch                    PENDING   0.53 seconds
GitLint                       PENDING   0.44 seconds
SubjectPrefix                 PASS      0.06 seconds
BuildKernel                   PASS      27.12 seconds
CheckAllWarning               PASS      29.57 seconds
CheckSparse                   PASS      28.25 seconds
BuildKernel32                 PASS      26.17 seconds
TestRunnerSetup               PASS      586.43 seconds
TestRunner_l2cap-tester       PASS      28.52 seconds
TestRunner_iso-tester         PASS      36.86 seconds
TestRunner_bnep-tester        PASS      6.44 seconds
TestRunner_mgmt-tester        FAIL      117.45 seconds
TestRunner_rfcomm-tester      PASS      9.69 seconds
TestRunner_sco-tester         FAIL      14.83 seconds
TestRunner_ioctl-tester       PASS      10.47 seconds
TestRunner_mesh-tester        FAIL      12.56 seconds
TestRunner_smp-tester         PASS      8.83 seconds
TestRunner_userchan-tester    PASS      6.71 seconds
TestRunner_6lowpan-tester     FAIL      8.83 seconds
IncrementalBuild              PENDING   0.35 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: 494, Passed: 489 (99.0%), Failed: 1, Not Run: 4

Failed Test Cases
Read Exp Feature - Success                           Failed       0.117 seconds
##############################
Test: TestRunner_sco-tester - FAIL
Desc: Run sco-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
7.0.0-rc2-ga495e056aeee #1 Not tainted
------------------------------------------------------
kworker/u5:2/117 is trying to acquire lock:
ffff888001945240 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_connect_cfm+0x358/0x8d0

but task is already holding lock:
ffff8880025f6220 (&conn->lock){+.+.}-{3:3}, at: sco_connect_cfm+0x22d/0x8d0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&conn->lock){+.+.}-{3:3}:
       lock_acquire+0xf7/0x2c0
       _raw_spin_lock+0x2a/0x40
       sco_sock_connect+0x4d7/0x1280
       __sys_connect+0x1a3/0x260
       __x64_sys_connect+0x6e/0xb0
       do_syscall_64+0xa0/0x570
       entry_SYSCALL_64_after_hwframe+0x74/0x7c

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       check_prev_add+0xe9/0xc70
       __lock_acquire+0x1457/0x1df0
       lock_acquire+0xf7/0x2c0
       lock_sock_nested+0x36/0xd0
       sco_connect_cfm+0x358/0x8d0
       hci_sync_conn_complete_evt+0x3d3/0x8e0
       hci_event_packet+0x74f/0xb10
       hci_rx_work+0x398/0xd00
       process_scheduled_works+0xb16/0x1ac0
       worker_thread+0x4ff/0xba0
       kthread+0x368/0x490
       ret_from_fork+0x498/0x7e0
       ret_from_fork_asm+0x19/0x30

other info that might help us debug this:

...
BUG: sleeping function called from invalid context at net/core/sock.c:3782
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 117, name: kworker/u5:2
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
INFO: lockdep is turned off.
CPU: 0 UID: 0 PID: 117 Comm: kworker/u5:2 Not tainted 7.0.0-rc2-ga495e056aeee #1 PREEMPT(lazy) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Workqueue: hci0 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x49/0x60
 __might_resched+0x2ea/0x500
 lock_sock_nested+0x47/0xd0
 ? sco_connect_cfm+0x358/0x8d0
 sco_connect_cfm+0x358/0x8d0
 ? hci_debugfs_create_conn+0x190/0x210
 ? __pfx_sco_connect_cfm+0x10/0x10
 hci_sync_conn_complete_evt+0x3d3/0x8e0
 hci_event_packet+0x74f/0xb10
 ? __pfx_hci_sync_conn_complete_evt+0x10/0x10
 ? __pfx_hci_event_packet+0x10/0x10
 ? mark_held_locks+0x49/0x80
 ? lockdep_hardirqs_on_prepare+0xd4/0x180
 ? _raw_spin_unlock_irqrestore+0x2c/0x50
 hci_rx_work+0x398/0xd00
 process_scheduled_works+0xb16/0x1ac0
 ? __pfx_process_scheduled_works+0x10/0x10
 ? lock_acquire+0xf7/0x2c0
 ? lock_is_held_type+0x9b/0x110
 ? __pfx_hci_rx_work+0x10/0x10
 worker_thread+0x4ff/0xba0
 ? _raw_spin_unlock_irqrestore+0x2c/0x50
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x368/0x490
 ? _raw_spin_unlock_irq+0x23/0x40
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x498/0x7e0
 ? __pfx_ret_from_fork+0x10/0x10
 ? __switch_to+0x9e4/0xe50
 ? __switch_to_asm+0x32/0x60
...
Total: 30, Passed: 30 (100.0%), Failed: 0, Not Run: 0
##############################
Test: TestRunner_mesh-tester - FAIL
Desc: Run mesh-tester with test-runner
Output:
Total: 10, Passed: 8 (80.0%), Failed: 2, Not Run: 0

Failed Test Cases
Mesh - Send cancel - 1                               Timed out    2.668 seconds
Mesh - Send cancel - 2                               Timed out    1.996 seconds
##############################
Test: TestRunner_6lowpan-tester - FAIL
Desc: Run 6lowpan-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
7.0.0-rc2-ga495e056aeee #1 Not tainted
------------------------------------------------------
kworker/0:1/10 is trying to acquire lock:
ffff888002476940 ((wq_completion)hci0#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x75/0x180

but task is already holding lock:
ffffffffa5e4d720 (rtnl_mutex){+.+.}-{4:4}, at: lowpan_unregister_netdev+0xd/0x30

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (rtnl_mutex){+.+.}-{4:4}:
       lock_acquire+0xf7/0x2c0
       __mutex_lock+0x16b/0x1fc0
       lowpan_register_netdev+0x11/0x30
       chan_ready_cb+0x836/0xd00
       l2cap_recv_frame+0x6a06/0x8920
       l2cap_recv_acldata+0x790/0xdf0
       hci_rx_work+0x500/0xd00
       process_scheduled_works+0xb16/0x1ac0
       worker_thread+0x4ff/0xba0
       kthread+0x368/0x490
       ret_from_fork+0x498/0x7e0
       ret_from_fork_asm+0x19/0x30

-> #3 (&chan->lock#3/1){+.+.}-{4:4}:
       lock_acquire+0xf7/0x2c0
       __mutex_lock+0x16b/0x1fc0
       l2cap_chan_connect+0x74e/0x1980
       lowpan_control_write+0x523/0x660
       full_proxy_write+0x10b/0x190
       vfs_write+0x1c0/0xf60
       ksys_write+0xf1/0x1d0
       do_syscall_64+0xa0/0x570
       entry_SYSCALL_64_after_hwframe+0x74/0x7c

-> #2 (&conn->lock){+.+.}-{4:4}:
...
Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



https://github.com/bluez/bluetooth-next/pull/35/checks

---
Regards,
Linux Bluetooth