Commit ad78b81a authored by Cristian Marussi's avatar Cristian Marussi Committed by Sudeep Holla
Browse files

firmware: arm_scmi: Harden shared memory access in fetch_response 



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

Harden shmem_fetch_response to properly truncate such a bad messages.

Fixes: 5c8a47a5 ("firmware: arm_scmi: Make scmi core independent of the transport type")
Signed-off-by: default avatarCristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222183823.518856-3-cristian.marussi@arm.com


Signed-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
parent f6ca5059

drivers/firmware/arm_scmi/shmem.c

+3 −2
Original line number Diff line number Diff line
@@ -81,10 +81,11 @@ u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem) 
void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,

			  struct scmi_xfer *xfer)

{

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



	xfer->hdr.status = ioread32(shmem->msg_payload);

	/* Skip the length of header and status in shmem area i.e 8 bytes */

	xfer->rx.len = min_t(size_t, xfer->rx.len,

			     ioread32(&shmem->length) - 8);

	xfer->rx.len = min_t(size_t, xfer->rx.len, len > 8 ? len - 8 : 0);



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

	memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);