From 096cdc6f52225835ff503f987a0d68ef770bb78e Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Tue, 21 Jun 2016 16:58:46 +0300 Subject: [PATCH] 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 Fixes: a841178445bb ('mfd: cros_ec: Use a zero-length array for command data') Signed-off-by: Dan Carpenter Reviewed-by: Kees Cook Tested-by: Gwendal Grignou Cc: # v4.2+ Signed-off-by: Olof Johansson --- drivers/platform/chrome/cros_ec_dev.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c index 6d8ee3b15872..8abd80dbcbed 100644 --- a/drivers/platform/chrome/cros_ec_dev.c +++ b/drivers/platform/chrome/cros_ec_dev.c @@ -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); -- 2.11.0