2022-03-17 05:19:22

by Hangyu Hua

[permalink] [raw]
Subject: [PATCH] can: m_can: fix a possible use after free in m_can_tx_handler()

can_put_echo_skb will clone skb then free the skb. It is better to avoid using
skb after can_put_echo_skb.

Signed-off-by: Hangyu Hua <[email protected]>
---
drivers/net/can/m_can/m_can.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 1a4b56f6fa8c..98be5742f4f5 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1607,6 +1607,7 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
u32 cccr, fdflags;
int err;
int putidx;
+ unsigned int len = skb->len;

cdev->tx_skb = NULL;

@@ -1642,7 +1643,7 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
if (cdev->can.ctrlmode & CAN_CTRLMODE_FD) {
cccr = m_can_read(cdev, M_CAN_CCCR);
cccr &= ~CCCR_CMR_MASK;
- if (can_is_canfd_skb(skb)) {
+ if (len == CANFD_MTU) {
if (cf->flags & CANFD_BRS)
cccr |= FIELD_PREP(CCCR_CMR_MASK,
CCCR_CMR_CANFD_BRS);
--
2.25.1


2022-03-17 08:34:02

by Marc Kleine-Budde

[permalink] [raw]
Subject: Re: [PATCH] can: m_can: fix a possible use after free in m_can_tx_handler()

On 17.03.2022 11:01:43, Hangyu Hua wrote:
> can_put_echo_skb will clone skb then free the skb. It is better to avoid using
> skb after can_put_echo_skb.

Why not move the can_put_echo_skb() instead? I'll send a patch.

Marc

--
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Embedded Linux | https://www.pengutronix.de |
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