This is a note to let you know that I've just added the patch titled
firmware: arm_scmi: Harden shared memory access in fetch_response
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
firmware-arm_scmi-harden-shared-memory-access-in-fet.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit a923ef0faad91ae716c124a1cf27aed6e8553ad5
Author: Cristian Marussi <cristian.marussi@xxxxxxx>
Date: Thu Dec 22 18:38:20 2022 +0000
firmware: arm_scmi: Harden shared memory access in fetch_response
[ 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>
diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c
index 1dfe534b8518..135f8718000f 100644
--- a/drivers/firmware/arm_scmi/shmem.c
+++ b/drivers/firmware/arm_scmi/shmem.c
@@ -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);
