From 3aef021b2df7d8440225a53460c0d34b140297d5 Mon Sep 17 00:00:00 2001
From: Tomas Winkler <tomas.winkler@intel.com>
Date: Tue, 11 Feb 2020 18:05:22 +0200
Subject: [PATCH] mei: limit number of bytes in mei header.
Git-commit: 3aef021b2df7d8440225a53460c0d34b140297d5
Patch-mainline: v5.7-rc1
References: jsc#SLE-13387
The MEI message header provides only 9 bits for storing
the message size, limiting to 511.
In theory the host buffer (hbuf) can contain up to 1020 bytes
(limited by byte = 255 * 4)
With the current hardware and hbuf size 512, this is not a real issue,
but as hardening approach we enforce the limit.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20200211160522.7562-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/misc/mei/client.c | 4 ++--
drivers/misc/mei/hw.h | 3 +++
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/misc/mei/client.c b/drivers/misc/mei/client.c
index 1e3edbbacb1e..204d807e755b 100644
--- a/drivers/misc/mei/client.c
+++ b/drivers/misc/mei/client.c
@@ -1585,7 +1585,7 @@ int mei_cl_irq_write(struct mei_cl *cl, struct mei_cl_cb *cb,
goto err;
}
- hbuf_len = mei_slots2data(hbuf_slots);
+ hbuf_len = mei_slots2data(hbuf_slots) & MEI_MSG_MAX_LEN_MASK;
dr_slots = mei_dma_ring_empty_slots(dev);
dr_len = mei_slots2data(dr_slots);
@@ -1718,7 +1718,7 @@ ssize_t mei_cl_write(struct mei_cl *cl, struct mei_cl_cb *cb)
goto out;
}
- hbuf_len = mei_slots2data(hbuf_slots);
+ hbuf_len = mei_slots2data(hbuf_slots) & MEI_MSG_MAX_LEN_MASK;
dr_slots = mei_dma_ring_empty_slots(dev);
dr_len = mei_slots2data(dr_slots);
diff --git a/drivers/misc/mei/hw.h b/drivers/misc/mei/hw.h
index d025a5f8317e..8231b6941adf 100644
--- a/drivers/misc/mei/hw.h
+++ b/drivers/misc/mei/hw.h
@@ -209,6 +209,9 @@ struct mei_msg_hdr {
u32 extension[0];
} __packed;
+/* The length is up to 9 bits */
+#define MEI_MSG_MAX_LEN_MASK GENMASK(9, 0)
+
#define MEI_MSG_HDR_MAX 2
struct mei_bus_message {
--
2.16.4