On Wed, Jul 15, 2020 at 11:07 PM Eric Biggers <[email protected]> wrote: > > From: Eric Biggers <[email protected]> > > 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 <[email protected]> > Cc: Arnd Bergmann <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Kees Cook <[email protected]> > Cc: Matthew Wilcox <[email protected]> > Cc: Russell King <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Greg Kroah-Hartman <[email protected]> > Fixes: 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims the > region") > Signed-off-by: Eric Biggers <[email protected]>
Makes sense: Acked-by: Dan Williams <[email protected]>
