2023-11-01 13:36:05

by Ren Mingshuai

Subject: [PATCH] tty: hso: Fix potential null pointer dereference

Generally, the old always points to the address of a ktermios structure,
so old is unlikely to be NULL. Still check it before dereference as
elsewhere.

Signed-off-by: Ren Mingshuai <[email protected]>
---
drivers/net/usb/hso.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index ce1f6081d582..4ad829ab54d3 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1396,7 +1396,8 @@ static void hso_serial_set_termios(struct tty_struct *tty,
if (serial->port.count)
_hso_serial_set_termios(tty);
else
- tty->termios = *old;
+ if (old)
+ tty->termios = *old;
spin_unlock_irqrestore(&serial->serial_lock, flags);

/* done */
--
2.33.0

2023-11-01 14:20:54

by Greg Kroah-Hartman

Subject: Re: [PATCH] tty: hso: Fix potential null pointer dereference

On Wed, Nov 01, 2023 at 09:35:44PM +0800, Ren Mingshuai wrote:
> Generally, the old always points to the address of a ktermios structure,
> so old is unlikely to be NULL. Still check it before dereference as
> elsewhere.

If it can not happen, there is no need to check it. So unless you can
prove that this ever could happen, this change isn't needed, right?

thanks,

greg k-h

2023-11-02 02:09:34

by Ren Mingshuai

Subject: Re: [PATCH] tty: hso: Fix potential null pointer dereference.

>> Generally, the old always points to the address of a ktermios structure,
>> so old is unlikely to be NULL. Still check it before dereference as
>> elsewhere.
>
>If it can not happen, there is no need to check it. So unless you can
>prove that this ever could happen, this change isn't needed, right?
>
>thanks,
>
>greg k-h
Thanks for reply. I agree with you. The reason for checking old there
is that it is checked at the beginning in hso_serial_set_termios(). It is
better to check it both or not, right?
Delete it to avoid smatch complaints.
drivers/net/usb/hso.c:1399 hso_serial_set_termios() error: we previously assumed 'old' could be null (see line 1389).

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 4ad829ab54d3..383ff8b04473 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1386,10 +1386,9 @@ static void hso_serial_set_termios(struct tty_struct *tty,
struct hso_serial *serial = tty->driver_data;
unsigned long flags;

- if (old)
- hso_dbg(0x16, "Termios called with: cflags new[%u] - old[%u]\n",
- (unsigned int)tty->termios.c_cflag,
- (unsigned int)old->c_cflag);
+ hso_dbg(0x16, "Termios called with: cflags new[%u] - old[%u]\n",
+ (unsigned int)tty->termios.c_cflag,
+ (unsigned int)old->c_cflag);

/* the actual setup */
spin_lock_irqsave(&serial->serial_lock, flags);