This reverts commit 84cb3df02aea4b00405521e67c4c67c2d525c364.
This commit solved the specific race condition mentioned in the commit:
"HCI_UART_PROTO_SET flag is set before hci_uart_set_proto call. If we
receive data from tty layer during this procedure, proto pointer may
not be assigned yet, leading to null pointer dereference in rx
method hci_uart_tty_receive.
This patch fixes this issue by introducing HCI_UART_PROTO_READY flag
in order to avoid any proto operation before proto opening and
assignment."
The design of the commit seems to be attempting to implement a
lockless solution by relying on atomic variables.
However, HCI_UART_PROTO_READY introduces a race condition here:
static int hci_uart_set_proto(struct hci_uart *hu,
...
hu->proto = p;
+ set_bit(HCI_UART_PROTO_READY, &hu->flags);
err = hci_uart_register_dev(hu);
if (err) {
+ clear_bit(HCI_UART_PROTO_READY, &hu->flags);
p->close(hu);
return err;
}
The issue here is that hci_uart_register_dev() allocates the
memory for hu->hdev and HCI_UART_PROTO_READY is set before
hdev is allocated. This means there is a risk that an unallocated hdev
is accessed because HCI_UART_PROTO_READY is set too early.
For example, hci_uart_tty_wakeup() used the HCI_UART_PROTO_READY flag
which means a transmission work item could potentially be scheduled
in hci_uart_tx_wakeup() when hdev has not been allocated.
Instead use a solution using locking supplied in commits:
"Bluetooth: Use single return in hci_uart_tty_ioctl() call"
"Bluetooth: Add mutex to hci_uart_tty_ioctl()"
"Bluetooth: Fix HCI UART HCI_UART_PROTO_SET locking"
Signed-off-by: Dean Jenkins <Dean_Jenkins@xxxxxxxxxx>
---
drivers/bluetooth/hci_ldisc.c | 11 ++++-------
drivers/bluetooth/hci_uart.h | 1 -
2 files changed, 4 insertions(+), 8 deletions(-)
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 1fc9817..499fb09 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -229,7 +229,7 @@ static int hci_uart_flush(struct hci_dev *hdev)
tty_ldisc_flush(tty);
tty_driver_flush_buffer(tty);
- if (test_bit(HCI_UART_PROTO_READY, &hu->flags))
+ if (test_bit(HCI_UART_PROTO_SET, &hu->flags))
hu->proto->flush(hu);
return 0;
@@ -494,7 +494,7 @@ static void hci_uart_tty_close(struct tty_struct *tty)
cancel_work_sync(&hu->write_work);
- if (test_and_clear_bit(HCI_UART_PROTO_READY, &hu->flags)) {
+ if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
if (hdev) {
if (test_bit(HCI_UART_REGISTERED, &hu->flags))
hci_unregister_dev(hdev);
@@ -502,7 +502,6 @@ static void hci_uart_tty_close(struct tty_struct *tty)
}
hu->proto->close(hu);
}
- clear_bit(HCI_UART_PROTO_SET, &hu->flags);
kfree(hu);
}
@@ -529,7 +528,7 @@ static void hci_uart_tty_wakeup(struct tty_struct *tty)
if (tty != hu->tty)
return;
- if (test_bit(HCI_UART_PROTO_READY, &hu->flags))
+ if (test_bit(HCI_UART_PROTO_SET, &hu->flags))
hci_uart_tx_wakeup(hu);
}
@@ -553,7 +552,7 @@ static void hci_uart_tty_receive(struct tty_struct *tty, const u8 *data,
if (!hu || tty != hu->tty)
return;
- if (!test_bit(HCI_UART_PROTO_READY, &hu->flags))
+ if (!test_bit(HCI_UART_PROTO_SET, &hu->flags))
return;
/* It does not need a lock here as it is already protected by a mutex in
@@ -641,11 +640,9 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)
return err;
hu->proto = p;
- set_bit(HCI_UART_PROTO_READY, &hu->flags);
err = hci_uart_register_dev(hu);
if (err) {
- clear_bit(HCI_UART_PROTO_READY, &hu->flags);
p->close(hu);
return err;
}
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index 0701395..f0707f4 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -97,7 +97,6 @@ struct hci_uart {
/* HCI_UART proto flag bits */
#define HCI_UART_PROTO_SET 0
#define HCI_UART_REGISTERED 1
-#define HCI_UART_PROTO_READY 2
/* TX states */
#define HCI_UART_SENDING 1
--
2.7.4
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