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mei: limit number of bytes in mei header.

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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>
This commit is contained in:
Tomas Winkler 2020-02-11 18:05:22 +02:00 committed by Greg Kroah-Hartman
parent 6736041f96
commit 3aef021b2d
2 changed files with 5 additions and 2 deletions
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4
drivers/misc/mei/client.c
View file

@ -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);

3
drivers/misc/mei/hw.h
View file

@ -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 {