linux-kernel - [PATCH] staging: fwserial: Fix potential NULL pointer dereferences

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Date:   Fri, 21 May 2021 14:43:39 +0300
From:   Evgeny Novikov <novikov@...ras.ru>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Evgeny Novikov <novikov@...ras.ru>,
        Johan Hovold <johan@...nel.org>,
        Nikolay Kyx <knv418@...il.com>,
        Dinghao Liu <dinghao.liu@....edu.cn>,
        Abheek Dhawan <adawesomeguy222@...il.com>,
        Lee Gibson <leegib@...il.com>, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: [PATCH] staging: fwserial: Fix potential NULL pointer dereferences

If fwtty_install() will be invoked with such tty->index that will be
not less than MAX_TOTAL_PORTS then fwtty_port_get() will return NULL and
fwtty_install() will either assign it to tty->driver_data or dereference
in fwtty_port_put() (if tty_standard_install() will fail). The similar
situation is with fwloop_install(). The patch fixes both cases.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Evgeny Novikov <novikov@...ras.ru>
---
 drivers/staging/fwserial/fwserial.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/staging/fwserial/fwserial.c b/drivers/staging/fwserial/fwserial.c
index 1ee6382cafc4..d0810896511e 100644
--- a/drivers/staging/fwserial/fwserial.c
+++ b/drivers/staging/fwserial/fwserial.c
@@ -1069,6 +1069,9 @@ static int fwtty_install(struct tty_driver *driver, struct tty_struct *tty)
 	struct fwtty_port *port = fwtty_port_get(tty->index);
 	int err;
 
+	if (!port)
+		return -ENODEV;
+
 	err = tty_standard_install(driver, tty);
 	if (!err)
 		tty->driver_data = port;
@@ -1082,6 +1085,9 @@ static int fwloop_install(struct tty_driver *driver, struct tty_struct *tty)
 	struct fwtty_port *port = fwtty_port_get(table_idx(tty->index));
 	int err;
 
+	if (!port)
+		return -ENODEV;
+
 	err = tty_standard_install(driver, tty);
 	if (!err)
 		tty->driver_data = port;
-- 
2.26.2