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firmware: arm_scmi: Harden shared memory access in fetch_notification

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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@arm.com>
Link: https://lore.kernel.org/r/20221222183823.518856-4-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
This commit is contained in:
Cristian Marussi 2022-12-22 18:38:21 +00:00 committed by Sudeep Holla
parent ad78b81a10
commit 9bae076cd4
1 changed files with 3 additions and 1 deletions
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4
drivers/firmware/arm_scmi/shmem.c
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@ -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);