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Commit 5d749d0b authored by Gwendal Grignou's avatar Gwendal Grignou Committed by Olof Johansson
Browse files

platform/chrome: cros_ec_dev - Fix security issue 



Prevent memory scribble by checking that ioctl buffer size parameters
are sane.
Without this check, on 32 bits system, if .insize = 0xffffffff - 20 and
.outsize the amount to scribble, we would overflow, allocate a small
amounts and be able to write outside of the malloc'ed area.
Adding a hard limit allows argument checking of the ioctl. With the
current EC, it is expected .insize and .outsize to be at around 512 bytes
or less.

Signed-off-by: default avatarGwendal Grignou <gwendal@chromium.org>
Signed-off-by: default avatarOlof Johansson <olof@lixom.net>
parent 492ef782

drivers/platform/chrome/cros_ec_dev.c

+4 −0
Original line number Diff line number Diff line
@@ -137,6 +137,10 @@ static long ec_device_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg) 
	if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))

		return -EFAULT;



	if ((u_cmd.outsize > EC_MAX_MSG_BYTES) ||

	    (u_cmd.insize > EC_MAX_MSG_BYTES))

		return -EINVAL;



	s_cmd = kmalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize),

			GFP_KERNEL);

	if (!s_cmd)

drivers/platform/chrome/cros_ec_proto.c

+2 −2
Original line number Diff line number Diff line
@@ -298,8 +298,8 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev) 
			ec_dev->max_response = EC_PROTO2_MAX_PARAM_SIZE;

			ec_dev->max_passthru = 0;

			ec_dev->pkt_xfer = NULL;

			ec_dev->din_size = EC_MSG_BYTES;

			ec_dev->dout_size = EC_MSG_BYTES;

			ec_dev->din_size = EC_PROTO2_MSG_BYTES;

			ec_dev->dout_size = EC_PROTO2_MSG_BYTES;

		} else {

			/*

			 * It's possible for a test to occur too early when

include/linux/mfd/cros_ec.h

+4 −2
Original line number Diff line number Diff line
@@ -50,9 +50,11 @@ enum { 
					EC_MSG_TX_TRAILER_BYTES,

	EC_MSG_RX_PROTO_BYTES	= 3,



	/* Max length of messages */

	EC_MSG_BYTES		= EC_PROTO2_MAX_PARAM_SIZE +

	/* Max length of messages for proto 2*/

	EC_PROTO2_MSG_BYTES		= EC_PROTO2_MAX_PARAM_SIZE +

					EC_MSG_TX_PROTO_BYTES,



	EC_MAX_MSG_BYTES		= 64 * 1024,

};



/*