Re: [PATCH v2 19/33] lib/zlib: Unpoison DFLTCC output buffers

[Ilya Leoshkevich]

On Fri, 2023-12-08 at 14:32 +0100, Alexander Potapenko wrote:
> On Tue, Nov 21, 2023 at 11:07 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> wrote:
> > 
> > The constraints of the DFLTCC inline assembly are not precise: they
> > do not communicate the size of the output buffers to the compiler,
> > so
> > it cannot automatically instrument it.
> 
> KMSAN usually does a poor job instrumenting inline assembly.
> Wouldn't be it better to switch to pure C ZLIB implementation, making
> ZLIB_DFLTCC depend on !KMSAN?

Normally I would agree, but the kernel DFLTCC code base is synced with
the zlib-ng code base to the extent that it uses the zlib-ng code style
instead of the kernel code style, and MSAN annotations are already a
part of the zlib-ng code base. So I would prefer to keep them for
consistency.

The code is also somewhat tricky in the are of buffer management, so I
find it beneficial to have it checked for uninitialized memory
accesses.