linux-kernel - Re: [PATCH v2] net: caif: fix memory leak in ldisc

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Message-ID: <2026011910-jubilance-supervise-00a0@gregkh>
Date: Mon, 19 Jan 2026 07:36:12 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Osama Abdelkader <osama.abdelkader@...il.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	"Jiri Slaby (SUSE)" <jirislaby@...nel.org>,
	Sjur Braendeland <sjur.brandeland@...ricsson.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzbot+f9d847b2b84164fa69f3@...kaller.appspotmail.com,
	stable@...r.kernel.org
Subject: Re: [PATCH v2] net: caif: fix memory leak in ldisc_receive

On Sun, Jan 18, 2026 at 06:44:16PM +0100, Osama Abdelkader wrote:
> Add NULL pointer checks for ser and ser->dev in ldisc_receive() to
> prevent memory leaks when the function is called during device close
> or in race conditions where tty->disc_data or ser->dev may be NULL.
> 
> The memory leak occurred because ser->dev was accessed before checking
> if ser or ser->dev was NULL, which could cause a NULL pointer
> dereference or use of freed memory. Additionally, set tty->disc_data
> to NULL in ldisc_close() to prevent receive_buf() from using a freed
> ser pointer after the line discipline is closed.
> 
> Reported-by: syzbot+f9d847b2b84164fa69f3@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=f9d847b2b84164fa69f3
> Fixes: 9b27105b4a44 ("net-caif-driver: add CAIF serial driver (ldisc)")
> CC: stable@...r.kernel.org
> Signed-off-by: Osama Abdelkader <osama.abdelkader@...il.com>
> ---
> v2:
> 1.Combine NULL pointer checks for ser and ser->dev in ldisc_receive()
> 2.Set tty->disc_data = NULL in ldisc_close() to prevent receive_buf()
> from using a freed ser pointer after close.
> 3.Add NULL pointer check for ser in ldisc_close()

I see no locking fixes, so I don't see how this will really work.

How do the other ldisc drivers handle this same issue?

thanks,

greg k-h