On Wed, Jul 15, 2020 at 11:07 PM Eric Biggers <ebigg...@kernel.org> wrote:
>
> From: Eric Biggers <ebigg...@google.com>
>
> WRITE_ONCE() isn't the correct way to publish a pointer to a data
> structure, since it doesn't include a write memory barrier. Therefore
> other tasks may see that the pointer has been set but not see that the
> pointed-to memory has finished being initialized yet. Instead a
> primitive with "release" semantics is needed.
>
> Use smp_store_release() for this.
>
> The use of READ_ONCE() on the read side is still potentially correct if
> there's no control dependency, i.e. if all memory being "published" is
> transitively reachable via the pointer itself. But this pairing is
> somewhat confusing and error-prone. So just upgrade the read side to
> smp_load_acquire() so that it clearly pairs with smp_store_release().
>
> Cc: Dan Williams <dan.j.willi...@intel.com>
> Cc: Arnd Bergmann <a...@arndb.de>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: Kees Cook <keesc...@chromium.org>
> Cc: Matthew Wilcox <wi...@infradead.org>
> Cc: Russell King <li...@arm.linux.org.uk>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> Fixes: 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims the
> region")
> Signed-off-by: Eric Biggers <ebigg...@google.com>
Makes sense:
Acked-by: Dan Williams <dan.j.willi...@intel.com>
