From: Cristian Marussi <cristian.marussi@xxxxxxx>
[ Upstream commit ad78b81a1077f7d956952cd8bdfe1e61504e3eb8 ]
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: 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of the transport type")
Signed-off-by: Cristian Marussi <cristian.marussi@xxxxxxx>
Link: https://lore.kernel.org/r/20221222183823.518856-3-cristian.marussi@xxxxxxx
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/firmware/arm_scmi/shmem.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c
index 0e3eaea5d852..415ef7df8fc3 100644
--- a/drivers/firmware/arm_scmi/shmem.c
+++ b/drivers/firmware/arm_scmi/shmem.c
@@ -58,10 +58,11 @@ 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);
--
2.39.0
