4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
commit 096cdc6f52225835ff503f987a0d68ef770bb78e upstream.
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@xxxxxxxxx>
Fixes: a841178445bb ('mfd: cros_ec: Use a zero-length array for command data')
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Tested-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
Signed-off-by: Olof Johansson <olof@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/platform/chrome/cros_ec_dev.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/platform/chrome/cros_ec_dev.c
+++ b/drivers/platform/chrome/cros_ec_dev.c
@@ -147,13 +147,19 @@ static long ec_device_ioctl_xcmd(struct
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);
--
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