From: Cristian Marussi <cristian.marussi@xxxxxxx>
[ Upstream commit 9bae076cd4e3e3c3dc185cae829d80b2dddec86e ]
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 <cristian.marussi@xxxxxxx>
Link: https://lore.kernel.org/r/20221222183823.518856-4-cristian.marussi@xxxxxxx
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/firmware/arm_scmi/shmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c
index 135f8718000f..87b4f4d35f06 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);
--
2.39.0
