Re: [PATCH] cred: remove const qualifiers

[David Howells <dhowells@redhat.com>]

Harvey Harrison <harvey.harrison@gmail.com> wrote:

> get_new_cred clearly writes through the pointer, so const isn't
> appropriate.  Sparse warns thusly:
> 
> include/linux/cred.h: In function ‘get_cred’:
> include/linux/cred.h:181: warning: passing argument 1 of ‘get_new_cred’ discards qualifiers from pointer target type

Sparse is wrong in this instance, it failed to note the cast.  I know what I'm
doing.

> -static inline const struct cred *get_cred(const struct cred *cred)
> +static inline struct cred *get_cred(struct cred *cred)

That will break the compilation.  Please don't do that.

The point of my use of const in this instance is to stop people from trying to
modify committed credentials directly, especially current->cred.  But we still
have to be able to take a reference to it.  Unfortunately, C does not provide
the necessary tools to do what I want.

Eventually, we can probably ditch the const marks on the pointers but not yet.

David