Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1348604

Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the NVMEM framework

Show all headers | View raw

On 03.03.2016 00:26, Andrew Lunn wrote:
>>>  static ssize_t
>>> -eeprom_93xx46_bin_read(struct file *filp, struct kobject *kobj,
>>> -		       struct bin_attribute *bin_attr,
>>> -		       char *buf, loff_t off, size_t count)
>>> +eeprom_93xx46_read(struct eeprom_93xx46_dev *edev, char *buf,
>>> +		   unsigned off, size_t count)
>>>  {
>>> -	struct eeprom_93xx46_dev *edev;
>>> -	struct device *dev;
>>>  	ssize_t ret = 0;
>>>  
>>> -	dev = kobj_to_dev(kobj);
>>> -	edev = dev_get_drvdata(dev);
>>> +	if (unlikely(off >= edev->size))
>>> +		return 0;
>>> +	if ((off + count) > edev->size)
>>> +		count = edev->size - off;
>>> +	if (unlikely(!count))
>>> +		return count;
>>>  
>>
>> I'm scratching my head, do you want to kind of revert
>> the change https://lkml.org/lkml/2015/7/26/89 ? Why?
> 
> Hi Vladimir
> 
> I had not noticed you had removed this.
>  
>> If you know regmap_config.max_register, then all necessary
>> boundary checks can be done inside NVMEM core.
> 
> You don't have to use NVMEM, you could use the regmap directly. 

No problem, regmap API from drivers/base/regmap/regmap.c contains
all necessary boundary checks as far as I understand.

> It is a public API. Also, during implementation, i did manage to get out of
> bounds read passed into the drivers and they caused a crash. That
> might of been AT24, i don't remember, but verifying is better than
> possible crashing.
> 

IMHO to avoid boilerplate code and/or missed/redundant checks it
might be better to handle this particular kind of problem only
in one common place, for example sysfs binary attribute files do
not need this anymore, probably I should scrutinize the situation
with this transition to NVMEM as well.

If you remember a reproduction scenario for that crash, please let
me know.

At least this changeset must be applied I guess, am I right?
In other words is the code without this changeset safe in connection
to boundary checks, and this is a new discovered issue?

--
With best wishes,
Vladimir

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCHv7 0/7] Convert exiting EEPROM drivers to NVMEM Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:00 +0100
  [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:00 +0100
    Re: [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM  framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-02 22:50 +0100
      Re: [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM  framework Andrew Lunn <andrew@lunn.ch> - 2016-03-02 22:50 +0100
        Re: [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM  framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-03 00:10 +0100
  [PATCHv7 5/7] eeprom: at25: extend driver to plug into the NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 5/7] eeprom: at25: extend driver to plug into the NVMEM  framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-02 23:00 +0100
  [PATCHv7 4/7] eeprom: at25: Remove in kernel API for accessing the EEPROM Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 4/7] eeprom: at25: Remove in kernel API for accessing  the EEPROM Wolfram Sang <wsa@the-dreams.de> - 2016-02-28 22:10 +0100
  [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the  NVMEM framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-02 23:10 +0100
      Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the  NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-03-02 23:30 +0100
        Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the  NVMEM framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-03 00:20 +0100
  [PATCHv7 7/7] misc: at24: replace memory_accessor with nvmem_device_read Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 7/7] misc: at24: replace memory_accessor with  nvmem_device_read Wolfram Sang <wsa@the-dreams.de> - 2016-02-28 22:10 +0100
  [PATCHv7 1/7] nvmem: Add flag to export NVMEM to root only Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
  [PATCHv7 2/7] nvmem: Add backwards compatibility support for older EEPROM drivers. Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
  Re: [PATCHv7 0/7] Convert exiting EEPROM drivers to NVMEM Greg KH <gregkh@linuxfoundation.org> - 2016-03-02 02:00 +0100

csiph-web