From linux-netdev Thu Jan 03 12:26:34 2019 From: Oliver Hartkopp Date: Thu, 03 Jan 2019 12:26:34 +0000 To: linux-netdev Subject: [PATCH] can: gw: ensure DLC boundaries after CAN frame modification Message-Id: <20190103122634.2530-1-socketcan () hartkopp ! net> X-MARC-Message: https://marc.info/?l=linux-netdev&m=154651842302479 The CAN frame modification rules allow bitwise logical operations which can be also applied to the can_dlc field. Ensure the manipulation result to maintain the can_dlc boundaries so that the CAN drivers do not accidently write arbitrary content beyond the data registers in the CAN controllers I/O mem when processing can-gw manipulated outgoing frames. When passing these frames to user space this issue did not have any effect to the kernel or any leaked data as we always strictly copy sizeof(struct can_frame) bytes. Reported-by: Muyu Yu Reported-by: Marcus Meissner Tested-by: Muyu Yu Signed-off-by: Oliver Hartkopp Cc: linux-stable # >= v3.2 --- net/can/gw.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/can/gw.c b/net/can/gw.c index faa3da88a127..9000d9b8a133 100644 --- a/net/can/gw.c +++ b/net/can/gw.c @@ -418,6 +418,10 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data) /* check for checksum updates when the CAN frame has been modified */ if (modidx) { + /* ensure DLC boundaries after the different mods */ + if (cf->can_dlc > 8) + cf->can_dlc = 8; + if (gwj->mod.csumfunc.crc8) (*gwj->mod.csumfunc.crc8)(cf, &gwj->mod.csum.crc8); -- 2.19.2