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As a skb length of CANFD_MTU can potentially be created with a CAN XL frame with a data length of 60, the length check of the CAN FD data length is used to detect CAN XL frames via its CANXL_XLF flag which exceeds valid CAN FD data length values. To make sure the CANFD_FDF flag can be safely used as a marker for CAN FD frame skbs the bit is set in can_send() which is used by all PF_CAN protocols. In the RX path alloc_canfd_skb() sets the CANFD_FDF flag. The enforced CANFD_FDF check in can_is_canfd_skb() clears up the potential uncertainty when using the skb->len check with the CANFD_MTU. Signed-off-by: Oliver Hartkopp --- include/linux/can/skb.h | 19 +++++++++++++++++-- net/can/af_can.c | 2 +- net/can/raw.c | 2 +- 3 files changed, 19 insertions(+), 4 deletions(-) diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h index 1abc25a8d144..09ab4dc83199 100644 --- a/include/linux/can/skb.h +++ b/include/linux/can/skb.h @@ -107,18 +107,33 @@ static inline bool can_is_can_skb(const struct sk_buff *skb) /* the CAN specific type of skb is identified by its data length */ return (skb->len == CAN_MTU && cf->len <= CAN_MAX_DLEN); } -static inline bool can_is_canfd_skb(const struct sk_buff *skb) +static inline bool can_is_canfd_skb_mtu_len(const struct sk_buff *skb) { struct canfd_frame *cfd = (struct canfd_frame *)skb->data; - /* the CAN specific type of skb is identified by its data length */ + /* The CAN specific type of skb is identified by its data length. + * A CAN XL frame skb might have a skb->len of CANFD_MTU but the + * skb would have the CANXL_XLF bit set (0x80 = 128) in the + * cfd->len field position which would intentionally break the + * CAN FD length check here. + */ return (skb->len == CANFD_MTU && cfd->len <= CANFD_MAX_DLEN); } +static inline bool can_is_canfd_skb(const struct sk_buff *skb) +{ + struct canfd_frame *cfd = (struct canfd_frame *)skb->data; + + if (!can_is_canfd_skb_mtu_len(skb)) + return false; + + return cfd->flags & CANFD_FDF; +} + static inline bool can_is_canxl_skb(const struct sk_buff *skb) { const struct canxl_frame *cxl = (struct canxl_frame *)skb->data; if (skb->len < CANXL_HDR_SIZE + CANXL_MIN_DLEN || skb->len > CANXL_MTU) diff --git a/net/can/af_can.c b/net/can/af_can.c index b2387a46794a..7fd2ed510440 100644 --- a/net/can/af_can.c +++ b/net/can/af_can.c @@ -207,11 +207,11 @@ int can_send(struct sk_buff *skb, int loop) if (can_is_canxl_skb(skb)) { skb->protocol = htons(ETH_P_CANXL); } else if (can_is_can_skb(skb)) { skb->protocol = htons(ETH_P_CAN); - } else if (can_is_canfd_skb(skb)) { + } else if (can_is_canfd_skb_mtu_len(skb)) { struct canfd_frame *cfd = (struct canfd_frame *)skb->data; skb->protocol = htons(ETH_P_CANFD); /* set CAN FD flag for CAN FD frames by default */ diff --git a/net/can/raw.c b/net/can/raw.c index 76b867d21def..e5e3952b0e09 100644 --- a/net/can/raw.c +++ b/net/can/raw.c @@ -886,11 +886,11 @@ static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb, /* Classical CAN -> no checks for flags and device capabilities */ if (can_is_can_skb(skb)) return CAN_MTU; /* CAN FD -> needs to be enabled and a CAN FD or CAN XL device */ - if (ro->fd_frames && can_is_canfd_skb(skb) && + if (ro->fd_frames && can_is_canfd_skb_mtu_len(skb) && (mtu == CANFD_MTU || can_is_canxl_dev_mtu(mtu))) return CANFD_MTU; /* CAN XL -> needs to be enabled and a CAN XL device */ if (ro->xl_frames && can_is_canxl_skb(skb) && -- 2.47.3