[PATCH] Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work

[PATCH] Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work

[Jia-Hong Su]

hci_uart_set_proto() sets HCI_UART_PROTO_INIT before calling
hci_uart_register_dev(), which calls proto->open() to initialize
hu->priv. However, if a TTY write wakeup occurs during this window,
hci_uart_tx_wakeup() may schedule write_work before hu->priv is
initialized, leading to a NULL pointer dereference in
hci_uart_write_work() when proto->dequeue() accesses hu->priv.

The race condition is:

  CPU0                              CPU1
  ----                              ----
  hci_uart_set_proto()
    set_bit(HCI_UART_PROTO_INIT)
    hci_uart_register_dev()
                                    tty write wakeup
                                      hci_uart_tty_wakeup()
                                        hci_uart_tx_wakeup()
                                          schedule_work(&hu->write_work)
      proto->open(hu)
        // initializes hu->priv
                                    hci_uart_write_work()
                                      hci_uart_dequeue()
                                        proto->dequeue(hu)
                                          // accesses hu->priv (NULL!)

Fix this by moving set_bit(HCI_UART_PROTO_INIT) after proto->open()
succeeds, ensuring hu->priv is initialized before any work can be
scheduled.

Fixes: 5df5dafc171b ("Bluetooth: hci_uart: Fix another race during initialization")
Link: https://lore.kernel.org/linux-bluetooth/6969764f.170a0220.2b9fc4.35a7@mx.google.com/

Signed-off-by: Jia-Hong Su <s11242586@gmail.com>
---
 drivers/bluetooth/hci_ldisc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index d0adae3267b4..2b28515de92c 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -685,6 +685,8 @@ static int hci_uart_register_dev(struct hci_uart *hu)
 		return err;
 	}
 
+	set_bit(HCI_UART_PROTO_INIT, &hu->flags);
+
 	if (test_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags))
 		return 0;
 
@@ -712,8 +714,6 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)
 
 	hu->proto = p;
 
-	set_bit(HCI_UART_PROTO_INIT, &hu->flags);
-
 	err = hci_uart_register_dev(hu);
 	if (err) {
 		return err;
-- 
2.34.1

RE: Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2593 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=1043777

---Test result---

Test Summary:
CheckPatch                    PENDING   0.32 seconds
GitLint                       PENDING   0.31 seconds
SubjectPrefix                 PASS      0.09 seconds
BuildKernel                   PASS      26.04 seconds
CheckAllWarning               PASS      27.60 seconds
CheckSparse                   PASS      31.89 seconds
BuildKernel32                 PASS      25.09 seconds
TestRunnerSetup               PASS      552.87 seconds
TestRunner_l2cap-tester       PASS      28.40 seconds
TestRunner_iso-tester         PASS      73.56 seconds
TestRunner_bnep-tester        PASS      6.26 seconds
TestRunner_mgmt-tester        FAIL      116.30 seconds
TestRunner_rfcomm-tester      PASS      9.47 seconds
TestRunner_sco-tester         FAIL      14.45 seconds
TestRunner_ioctl-tester       PASS      10.11 seconds
TestRunner_mesh-tester        FAIL      11.46 seconds
TestRunner_smp-tester         PASS      8.60 seconds
TestRunner_userchan-tester    PASS      6.75 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: 494, Passed: 489 (99.0%), Failed: 1, Not Run: 4

Failed Test Cases
Read Exp Feature - Success                           Failed       0.105 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    1.870 seconds
Mesh - Send cancel - 2                               Timed out    1.996 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH] Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work

[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 Sun, 18 Jan 2026 20:08:59 +0800 you wrote:
> hci_uart_set_proto() sets HCI_UART_PROTO_INIT before calling
> hci_uart_register_dev(), which calls proto->open() to initialize
> hu->priv. However, if a TTY write wakeup occurs during this window,
> hci_uart_tx_wakeup() may schedule write_work before hu->priv is
> initialized, leading to a NULL pointer dereference in
> hci_uart_write_work() when proto->dequeue() accesses hu->priv.
> 
> [...]

Here is the summary with links:
  - Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work
    https://git.kernel.org/bluetooth/bluetooth-next/c/1d8551ecf806

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