Commit 096cdc6f authored Jun 21, 2016 by Dan Carpenter Committed by Olof Johansson Jul 05, 2016

platform/chrome: cros_ec_dev - double fetch bug in ioctl



We verify "u_cmd.outsize" and "u_cmd.insize" but we need to make sure
that those values have not changed between the two copy_from_user()
calls.  Otherwise it could lead to a buffer overflow.

Additionally, cros_ec_cmd_xfer() can set s_cmd->insize to a lower value.
We should use the new smaller value so we don't copy too much data to
the user.

Reported-by: Pengfei Wang <wpengfeinudt@gmail.com>
Fixes: a8411784 ('mfd: cros_ec: Use a zero-length array for command data')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Cc: <stable@vger.kernel.org> # v4.2+
Signed-off-by: Olof Johansson <olof@lixom.net>

parent 33688abb

drivers/platform/chrome/cros_ec_dev.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -151,13 +151,19 @@ static long ec_device_ioctl_xcmd(struct cros_ec_dev ec, void __user arg)
		goto exit;
		}

		if (u_cmd.outsize != s_cmd->outsize \|\|
		u_cmd.insize != s_cmd->insize) {
		ret = -EINVAL;
		goto exit;
		}

		s_cmd->command += ec->cmd_offset;
		ret = cros_ec_cmd_xfer(ec->ec_dev, s_cmd);
		/* Only copy data to userland if data was received. */
		if (ret < 0)
		goto exit;

		if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + u_cmd.insize))
		if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
		ret = -EFAULT;
		exit:
		kfree(s_cmd);