Re: [PATCH v2 1/6] KEYS: fix race between updating and finding negative key

Eric Biggers
2017-09-26T20:39:15Z

On Tue, Sep 26, 2017 at 01:11:00PM -0700, Eric Biggers wrote:
> +static void mark_key_instantiated(struct key *key, unsigned int reject_error)
> +{
> + unsigned long old, new;
> +
> + do {
> + old = READ_ONCE(key->flags);
> + new = (old & ~(KEY_FLAG_NEGATIVE |
> + KEY_FLAGS_REJECT_ERROR_MASK)) |
> + KEY_FLAG_INSTANTIATED |
> + (reject_error ? KEY_FLAG_NEGATIVE : 0) |
> + (reject_error << KEY_FLAGS_REJECT_ERROR_SHIFT);
> + } while (cmpxchg_release(&key->flags, old, new) != old);
> +}

Sorry, I realized I screwed this up --- the flags like KEY_FLAG_NEGATIVE need to
be (1 << KEY_FLAG_NEGATIVE). I'll send another version which will be better
tested...

Eric