Commit 9bae076c authored by Cristian Marussi's avatar Cristian Marussi Committed by Sudeep Holla
Browse files

firmware: arm_scmi: Harden shared memory access in fetch_notification 



A misbheaving SCMI platform firmware could reply with out-of-spec
notifications, shorter than the mimimum size comprising a header.

Fixes: d5141f37 ("firmware: arm_scmi: Add notifications support in transport layer")
Signed-off-by: default avatarCristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222183823.518856-4-cristian.marussi@arm.com


Signed-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
parent ad78b81a

drivers/firmware/arm_scmi/shmem.c

+3 −1
Original line number Diff line number Diff line
@@ -94,8 +94,10 @@ void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem, 
void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,

			      size_t max_len, struct scmi_xfer *xfer)

{

	size_t len = ioread32(&shmem->length);



	/* Skip only the length of header in shmem area i.e 4 bytes */

	xfer->rx.len = min_t(size_t, max_len, ioread32(&shmem->length) - 4);

	xfer->rx.len = min_t(size_t, max_len, len > 4 ? len - 4 : 0);



	/* Take a copy to the rx buffer.. */

	memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);