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From 096cdc6f52225835ff503f987a0d68ef770bb78e Mon Sep 17 00:00:00 2001
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From: Dan Carpenter <dan.carpenter@oracle.com>
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Date: Tue, 21 Jun 2016 16:58:46 +0300
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Subject: [PATCH] platform/chrome: cros_ec_dev - double fetch bug in ioctl
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We verify "u_cmd.outsize" and "u_cmd.insize" but we need to make sure
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that those values have not changed between the two copy_from_user()
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calls. Otherwise it could lead to a buffer overflow.
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Additionally, cros_ec_cmd_xfer() can set s_cmd->insize to a lower value.
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We should use the new smaller value so we don't copy too much data to
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the user.
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Reported-by: Pengfei Wang <wpengfeinudt@gmail.com>
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Fixes: a841178445bb ('mfd: cros_ec: Use a zero-length array for command data')
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Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
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Reviewed-by: Kees Cook <keescook@chromium.org>
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Tested-by: Gwendal Grignou <gwendal@chromium.org>
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Cc: <stable@vger.kernel.org> # v4.2+
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Signed-off-by: Olof Johansson <olof@lixom.net>
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---
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drivers/platform/chrome/cros_ec_dev.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
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index 6d8ee3b15872..8abd80dbcbed 100644
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--- a/drivers/platform/chrome/cros_ec_dev.c
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+++ b/drivers/platform/chrome/cros_ec_dev.c
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@@ -151,13 +151,19 @@ static long ec_device_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg)
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goto exit;
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}
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+ if (u_cmd.outsize != s_cmd->outsize ||
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+ u_cmd.insize != s_cmd->insize) {
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+ ret = -EINVAL;
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+ goto exit;
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+ }
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+
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s_cmd->command += ec->cmd_offset;
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ret = cros_ec_cmd_xfer(ec->ec_dev, s_cmd);
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/* Only copy data to userland if data was received. */
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if (ret < 0)
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goto exit;
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- if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + u_cmd.insize))
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+ if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
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ret = -EFAULT;
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exit:
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kfree(s_cmd);
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--
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2.5.5
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