Quoting Sebastian Capella (2013-10-03 16:47:35)

Quoting Sebastian Capella (2013-10-03 14:42:46)

quoted

Quoting Andrew Morton (2013-10-03 14:15:23)

quoted

On Thu,  3 Oct 2013 14:10:37 -0700 Sebastian Capella [off-list ref] wrote:

quoted

Enhance name_to_dev_t to handle trailing newline characters
on device paths.  Some inputs to name_to_dev_t may come from
userspace where oftentimes a '\n' is appended to the path.
Added const to the name buffer in both the function
declaration and the prototype to reflect input buffer
handling.

By handling trailing newlines in name_to_dev_t, userspace
buffers may be directly passed to name_to_dev_t without
modification.

We have lib/string.c:strim() - perhaps this patch would be
neater if it were to use it?

Hi Morton,

I was intending to respect the const handling of the input buffer.

The actual buffer in this case is not really const as it comes from
the file buffering, but removing the const requires changing the
store function defined in the kobj_attribute, and would propagate
to many areas in the kernel.

Modifying the buffer and removing the const was also suggested by Pavel.
After some discussion I posted this version which did not change the
buffer or the prototype.

Please let me know if the preference is to modify the store function
definition.

I'll prepare a patchset that removes the consts to see how much is
changed.

Thanks,

Sebastian

Hi Andrew,

Sorry for calling you Morton earlier.

I looked into removing the const from the store function, but I'm not sure
this is the right idea, so I'm going to shelf that for now.

Please let me know your thoughts.

Thanks,

Sebastian

 
Ping...

Hi Andrew,

Do you have any feedback on this?

Below are the three options considered thus far.  Do
you have any additional suggestions or preferences?

Thanks,

Sebastian


1) copy buffer, remove \n.
  - v1 patch did this
  - alternatively could use an array on the stack or a preallocated global
    Pros:
     . cleanest change
    Cons:
     . adds memcpy
2) make name_to_dev_t work with readonly buffer to ignore \n
  - v2 and v3 patches do this
    Pros:
     . no memcpy, no big modifications to unrelated code
    Cons:
     . seems more appropriate to harden store functions to user input
       than name_to_dev_t.
     . a little complicated
3) remove const from buffer and modify contents in place to remove \n
  - remove const from sysfs_ops.store, modify dependent definitions
  - remove const from kobj_attribute.store, modify dependent definitions
    Pros:
     . no memcpy
    Cons:
     . a lot of modifications
     . const contract to not modify the input buffer seems the right way.