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([2a02:908:1b4:dac0:5466:5c6:1ae0:13b7]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-65452bce411sm8105189a12.7.2026.01.18.09.45.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 18 Jan 2026 09:45:28 -0800 (PST) From: Osama Abdelkader To: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Greg Kroah-Hartman , "Jiri Slaby (SUSE)" , Osama Abdelkader , Sjur Braendeland , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: syzbot+f9d847b2b84164fa69f3@syzkaller.appspotmail.com, stable@vger.kernel.org Subject: [PATCH v2] net: caif: fix memory leak in ldisc_receive Date: Sun, 18 Jan 2026 18:44:16 +0100 Message-ID: <20260118174422.10257-1-osama.abdelkader@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Df9d847b2b84164fa69f3 Fixes: 9b27105b4a44 ("net-caif-driver: add CAIF serial driver (ldisc)") CC: stable@vger.kernel.org Signed-off-by: Osama Abdelkader --- v2: 1.Combine NULL pointer checks for ser and ser->dev in ldisc_receive() 2.Set tty->disc_data =3D 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() --- drivers/net/caif/caif_serial.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c index c398ac42eae9..970237a3ccca 100644 --- a/drivers/net/caif/caif_serial.c +++ b/drivers/net/caif/caif_serial.c @@ -152,6 +152,8 @@ static void ldisc_receive(struct tty_struct *tty, const= u8 *data, int ret; =20 ser =3D tty->disc_data; + if (!ser || !ser->dev) + return; =20 /* * NOTE: flags may contain information about break or overrun. @@ -170,8 +172,6 @@ static void ldisc_receive(struct tty_struct *tty, const= u8 *data, return; } =20 - BUG_ON(ser->dev =3D=3D NULL); - /* Get a suitable caif packet and copy in data. */ skb =3D netdev_alloc_skb(ser->dev, count+1); if (skb =3D=3D NULL) @@ -355,11 +355,15 @@ static void ldisc_close(struct tty_struct *tty) { struct ser_device *ser =3D tty->disc_data; =20 + if (!ser) + return; + tty_kref_put(ser->tty); =20 spin_lock(&ser_lock); list_move(&ser->node, &ser_release_list); spin_unlock(&ser_lock); + tty->disc_data =3D NULL; schedule_work(&ser_release_work); } =20 --=20 2.43.0