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firmware: arm_scmi: Harden shared memory access in fetch_response

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[ 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: 5c8a47a5a9 ("firmware: arm_scmi: Make scmi core independent of the transport type")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222183823.518856-3-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Cristian Marussi 2022-12-22 18:38:20 +00:00 committed by Greg Kroah-Hartman
parent b7863ef8a8
commit 3463203d10
1 changed files with 3 additions and 2 deletions
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5
drivers/firmware/arm_scmi/shmem.c
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@ -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);