Re: [PATCH v14 04/19] x86/uaccess: Add unsafe_copy_from_user() implementation

[Steven Rostedt <rostedt@kernel.org>]

On Wed, 6 May 2026 16:13:25 +0200
Jens Remus <jremus@linux.ibm.com> wrote:

> > Regarding the variable naming in the updated unsafe_copy_to_user() and the
> > new unsafe_copy_from_user() macros, is there a risk of variable shadowing?
> > 
> > The macros declare local variables with very common names, specifically __dst,
> > __src, and __len. If a caller passes an argument that happens to share one of
> > these names, the local variable declaration will shadow the caller's argument.
> > For instance, if a caller passes __len, the initialization size_t __len =
> > (_len); will evaluate the right-hand side as the newly declared uninitialized
> > local variable itself. Could this lead to the loop copying a random length of
> > memory based on stack garbage instead of the intended length? The previous
> > implementation seemed to avoid this by using uniquely prefixed names like
> > __ucu_len.  
> 
> Please advise.

There is an effort to get rid of common variable names in macros that
start with underscores. But honestly, that can be dealt with later, as
it's a problem with other macros in this header.

Feel free to ignore this suggestion.

-- Steve