Re: [PATCH 1/3] drivers: staging: wilc1000: Check for errors before kfree

Dan Carpenter
2015-10-02T13:39:35Z

On Fri, Oct 02, 2015 at 06:47:35PM +0530, Chandra S Gorentla wrote:
> During the clean-up of the function, it is need to check if
> errors occurred, not the memory pointer.
>

The bug here is that we have a use after free on the success path. It
should have been mentioned in the changelog.

Anyway, this patch is buggy. If result == -EFAULT then it will crash.
Also this patch is really ugly. There is someone who is going to send a
correct fix (just add a return 0).

This driver usese "do everything" style error handling. It is a bug
prone anti-pattern because doing everything is more complicated than
doing one thing. You can easily see it is bug prone, because it made
you introduce a bug, right?

Instead the error handling should look like this:

return 0;

err_free_msg:
kfree(pstrMessage);

return ret;

There are no error paths where we need to free "pstrMessage->pvBuffer"
but if we were to add one it would look like this:

return 0;

err_pvbuffer:
kfree(pstrMessage->pvBuffer);
err_msg:
kfree(pstrMessage);

return ret;

This is a minimal, uncomplicated, no indenting, no if statement way of
unwinding.

regards,
dan carpenter