From: Cristian Marussi Date: Thu, 22 Dec 2022 18:38:21 +0000 (+0000) Subject: firmware: arm_scmi: Harden shared memory access in fetch_notification X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9bae076cd4e3e3c3dc185cae829d80b2dddec86e;p=linux.git 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: d5141f37c42e ("firmware: arm_scmi: Add notifications support in transport layer") Signed-off-by: Cristian Marussi Link: https://lore.kernel.org/r/20221222183823.518856-4-cristian.marussi@arm.com Signed-off-by: Sudeep Holla --- diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c index 135f8718000f5..87b4f4d35f062 100644 --- a/drivers/firmware/arm_scmi/shmem.c +++ b/drivers/firmware/arm_scmi/shmem.c @@ -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);