[PATCH 6.18 080/277] Bluetooth: hci_h4: Fix race during initialization

Greg Kroah-Hartman
2026-04-08T18:32:09Z

From: Jonathan Rissanen <jonathan.rissanen@axis.com>

[ Upstream commit 0ffac654e95c1bdfe2d4edf28fb18d6ba1f103e6 ]

Commit 5df5dafc171b ("Bluetooth: hci_uart: Fix another race during
initialization") fixed a race for hci commands sent during initialization.
However, there is still a race that happens if an hci event from one of
these commands is received before HCI_UART_REGISTERED has been set at
the end of hci_uart_register_dev(). The event will be ignored which
causes the command to fail with a timeout in the log:

"Bluetooth: hci0: command 0x1003 tx timeout"

This is because the hci event receive path (hci_uart_tty_receive ->
h4_recv) requires HCI_UART_REGISTERED to be set in h4_recv(), while the
hci command transmit path (hci_uart_send_frame -> h4_enqueue) only
requires HCI_UART_PROTO_INIT to be set in hci_uart_send_frame().

The check for HCI_UART_REGISTERED was originally added in commit
c2578202919a ("Bluetooth: Fix H4 crash from incoming UART packets")
to fix a crash caused by hu->hdev being null dereferenced. That can no
longer happen: once HCI_UART_PROTO_INIT is set in hci_uart_register_dev()
all pointers (hu, hu->priv and hu->hdev) are valid, and
hci_uart_tty_receive() already calls h4_recv() on HCI_UART_PROTO_INIT
or HCI_UART_PROTO_READY.

Remove the check for HCI_UART_REGISTERED in h4_recv() to fix the race
condition.

Fixes: 5df5dafc171b ("Bluetooth: hci_uart: Fix another race during initialization")
Signed-off-by: Jonathan Rissanen <jonathan.rissanen@axis.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/bluetooth/hci_h4.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
index ec017df8572c8..1e9e2cad9ddf6 100644
--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -109,9 +109,6 @@ static int h4_recv(struct hci_uart *hu, const void *data, int count)
{
struct h4_struct *h4 = hu->priv;

- if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
- return -EUNATCH;
-
h4->rx_skb = h4_recv_buf(hu, h4->rx_skb, data, count,
h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
if (IS_ERR(h4->rx_skb)) {
--
2.53.0