Re: [PATCH 17/32] staging: gasket: annotate ioctl arg with __user

From: Greg Kroah-Hartman
Date: Thu Jul 19 2018 - 05:37:51 EST

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In reply to: Todd Poynor: "[PATCH 17/32] staging: gasket: annotate ioctl arg with __user"
Next in thread: Todd Poynor: "Re: [PATCH 17/32] staging: gasket: annotate ioctl arg with __user"
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On Tue, Jul 17, 2018 at 01:56:57PM -0700, Todd Poynor wrote:
> From: Todd Poynor <toddpoynor@xxxxxxxxxx>
>
> For sparse checking.

Close, but you can do better :)

>
> Reported-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
> Signed-off-by: Zhongze Hu <frankhu@xxxxxxxxxxxx>
> Signed-off-by: Todd Poynor <toddpoynor@xxxxxxxxxx>
> Reviewed-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
> ---
> drivers/staging/gasket/apex_driver.c | 11 ++--
> drivers/staging/gasket/gasket_core.c | 6 ++-
> drivers/staging/gasket/gasket_core.h | 4 +-
> drivers/staging/gasket/gasket_ioctl.c | 72 ++++++++++++++-------------
> drivers/staging/gasket/gasket_ioctl.h | 4 +-
> 5 files changed, 52 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/staging/gasket/apex_driver.c b/drivers/staging/gasket/apex_driver.c
> index 612b3ab803196..c91c5aff5ab9c 100644
> --- a/drivers/staging/gasket/apex_driver.c
> +++ b/drivers/staging/gasket/apex_driver.c
> @@ -5,6 +5,7 @@
> * Copyright (C) 2018 Google, Inc.
> */
>
> +#include <linux/compiler.h>
> #include <linux/delay.h>
> #include <linux/fs.h>
> #include <linux/init.h>
> @@ -142,9 +143,9 @@ static int apex_get_status(struct gasket_dev *gasket_dev);
>
> static uint apex_ioctl_check_permissions(struct file *file, uint cmd);
>
> -static long apex_ioctl(struct file *file, uint cmd, ulong arg);
> +static long apex_ioctl(struct file *file, uint cmd, void __user *arg);
>
> -static long apex_clock_gating(struct gasket_dev *gasket_dev, ulong arg);
> +static long apex_clock_gating(struct gasket_dev *gasket_dev, void __user *arg);

Make this a __user pointer to the correct struct type you are handling
here. You know what the type is, use it.

> static int apex_enter_reset(struct gasket_dev *gasket_dev, uint type);
>
> @@ -635,7 +636,7 @@ static uint apex_ioctl_check_permissions(struct file *filp, uint cmd)
> /*
> * Apex-specific ioctl handler.
> */
> -static long apex_ioctl(struct file *filp, uint cmd, ulong arg)
> +static long apex_ioctl(struct file *filp, uint cmd, void __user *arg)
> {
> struct gasket_dev *gasket_dev = filp->private_data;
>
> @@ -655,7 +656,7 @@ static long apex_ioctl(struct file *filp, uint cmd, ulong arg)
> * @gasket_dev: Gasket device pointer.
> * @arg: User ioctl arg, in this case to a apex_gate_clock_ioctl struct.
> */
> -static long apex_clock_gating(struct gasket_dev *gasket_dev, ulong arg)
> +static long apex_clock_gating(struct gasket_dev *gasket_dev, void __user *arg)

As above, this should be a different type.

> {
> struct apex_gate_clock_ioctl ibuf;
>
> @@ -663,7 +664,7 @@ static long apex_clock_gating(struct gasket_dev *gasket_dev, ulong arg)
> return 0;
>
> if (allow_sw_clock_gating) {
> - if (copy_from_user(&ibuf, (void __user *)arg, sizeof(ibuf)))
> + if (copy_from_user(&ibuf, arg, sizeof(ibuf)))
> return -EFAULT;
>
> gasket_log_error(
> diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c
> index 947b4fcc76970..ff34af42bbe7c 100644
> --- a/drivers/staging/gasket/gasket_core.c
> +++ b/drivers/staging/gasket/gasket_core.c
> @@ -14,6 +14,7 @@
> #include "gasket_page_table.h"
> #include "gasket_sysfs.h"
>
> +#include <linux/compiler.h>
> #include <linux/delay.h>
> #include <linux/fs.h>
> #include <linux/init.h>
> @@ -1823,14 +1824,15 @@ static long gasket_ioctl(struct file *filp, uint cmd, ulong arg)
> * check_and_invoke_callback.
> */
> if (driver_desc->ioctl_handler_cb)
> - return driver_desc->ioctl_handler_cb(filp, cmd, arg);
> + return driver_desc->ioctl_handler_cb(
> + filp, cmd, (void __user *)arg);

You can use a temp variable and then only have to cast things once then,
instead of twice, if you care. Not a big deal.

>
> gasket_log_error(
> gasket_dev, "Received unknown ioctl 0x%x", cmd);

This is a fun way to cause a DoS on your system, you should fix this up
in later changes.

> return -EINVAL;
> }
>
> - return gasket_handle_ioctl(filp, cmd, arg);
> + return gasket_handle_ioctl(filp, cmd, (void __user *)arg);
> }
>
> int gasket_reset(struct gasket_dev *gasket_dev, uint reset_type)
> diff --git a/drivers/staging/gasket/gasket_core.h b/drivers/staging/gasket/gasket_core.h
> index 50ad0c8853183..68b4d2ac9fd6c 100644
> --- a/drivers/staging/gasket/gasket_core.h
> +++ b/drivers/staging/gasket/gasket_core.h
> @@ -315,7 +315,7 @@ struct gasket_dev {
>
> /* Type of the ioctl permissions check callback. See below. */
> typedef int (*gasket_ioctl_permissions_cb_t)(
> - struct file *filp, uint cmd, ulong arg);
> + struct file *filp, uint cmd, void __user *arg);
>
> /*
> * Device type descriptor.
> @@ -549,7 +549,7 @@ struct gasket_driver_desc {
> * return -EINVAL. Should return an error status (either -EINVAL or
> * the error result of the ioctl being handled).
> */
> - long (*ioctl_handler_cb)(struct file *filp, uint cmd, ulong arg);
> + long (*ioctl_handler_cb)(struct file *filp, uint cmd, void __user *arg);

Why are you not using the typedef above?

>
> /*
> * device_status_cb: Callback to determine device health.
> diff --git a/drivers/staging/gasket/gasket_ioctl.c b/drivers/staging/gasket/gasket_ioctl.c
> index d0fa05b8bf1d3..ab2376c32c00b 100644
> --- a/drivers/staging/gasket/gasket_ioctl.c
> +++ b/drivers/staging/gasket/gasket_ioctl.c
> @@ -7,6 +7,7 @@
> #include "gasket_interrupt.h"
> #include "gasket_logging.h"
> #include "gasket_page_table.h"
> +#include <linux/compiler.h>
> #include <linux/fs.h>
> #include <linux/uaccess.h>
>
> @@ -23,17 +24,18 @@
> #endif
>
> static uint gasket_ioctl_check_permissions(struct file *filp, uint cmd);
> -static int gasket_set_event_fd(struct gasket_dev *dev, ulong arg);
> +static int gasket_set_event_fd(struct gasket_dev *dev, void __user *arg);
> static int gasket_read_page_table_size(
> - struct gasket_dev *gasket_dev, ulong arg);
> + struct gasket_dev *gasket_dev, void __user *arg);
> static int gasket_read_simple_page_table_size(
> - struct gasket_dev *gasket_dev, ulong arg);
> + struct gasket_dev *gasket_dev, void __user *arg);
> static int gasket_partition_page_table(
> - struct gasket_dev *gasket_dev, ulong arg);
> -static int gasket_map_buffers(struct gasket_dev *gasket_dev, ulong arg);
> -static int gasket_unmap_buffers(struct gasket_dev *gasket_dev, ulong arg);
> + struct gasket_dev *gasket_dev, void __user *arg);
> +static int gasket_map_buffers(struct gasket_dev *gasket_dev, void __user *arg);
> +static int gasket_unmap_buffers(struct gasket_dev *gasket_dev,
> + void __user *arg);
> static int gasket_config_coherent_allocator(
> - struct gasket_dev *gasket_dev, ulong arg);
> + struct gasket_dev *gasket_dev, void __user *arg);

For most of these you know the real type, please just use it.

> /*
> * standard ioctl dispatch function.
> @@ -43,9 +45,10 @@ static int gasket_config_coherent_allocator(
> *
> * Standard ioctl dispatcher; forwards operations to individual handlers.
> */
> -long gasket_handle_ioctl(struct file *filp, uint cmd, ulong arg)
> +long gasket_handle_ioctl(struct file *filp, uint cmd, void __user *arg)
> {
> struct gasket_dev *gasket_dev;
> + ulong intarg = (ulong)arg;

Ick, really? That's a horrible name for a variable, especially as it
doesn't describe what it is...

and "unsigned long" please, ulong is not a "real" kernel type.

> int retval;
>
> gasket_dev = (struct gasket_dev *)filp->private_data;
> @@ -74,16 +77,16 @@ long gasket_handle_ioctl(struct file *filp, uint cmd, ulong arg)
> */
> switch (cmd) {
> case GASKET_IOCTL_RESET:
> - trace_gasket_ioctl_integer_data(arg);
> - retval = gasket_reset(gasket_dev, arg);
> + trace_gasket_ioctl_integer_data(intarg);
> + retval = gasket_reset(gasket_dev, intarg);
> break;
> case GASKET_IOCTL_SET_EVENTFD:
> retval = gasket_set_event_fd(gasket_dev, arg);
> break;
> case GASKET_IOCTL_CLEAR_EVENTFD:
> - trace_gasket_ioctl_integer_data(arg);
> + trace_gasket_ioctl_integer_data(intarg);
> retval = gasket_interrupt_clear_eventfd(
> - gasket_dev->interrupt_data, (int)arg);
> + gasket_dev->interrupt_data, (int)intarg);

See, look at that cast, why would you ever think to cast a variabled
with "int" in the name of it, to an int? Naming is hard :(

> break;
> case GASKET_IOCTL_PARTITION_PAGE_TABLE:
> trace_gasket_ioctl_integer_data(arg);
> @@ -91,7 +94,7 @@ long gasket_handle_ioctl(struct file *filp, uint cmd, ulong arg)
> break;
> case GASKET_IOCTL_NUMBER_PAGE_TABLES:
> trace_gasket_ioctl_integer_data(gasket_dev->num_page_tables);
> - if (copy_to_user((void __user *)arg,
> + if (copy_to_user(arg,
> &gasket_dev->num_page_tables,

Nit, you can move this line up one now.

I'll stop now, you get the idea. This should be broken up a lot.

thanks,

greg k-h

Next message: Benjamin Tissoires: "Re: [PATCH v2] HID: intel-ish-hid: Prevent loading of driver on Mehlow"
Previous message: Oleksandr Andrushchenko: "[PATCH v3] drm: Replace NULL with error value in drm_prime_pages_to_sg"
In reply to: Todd Poynor: "[PATCH 17/32] staging: gasket: annotate ioctl arg with __user"
Next in thread: Todd Poynor: "Re: [PATCH 17/32] staging: gasket: annotate ioctl arg with __user"
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