Re: [PATCH] KEYS: Use acquire when reading state in keyring search

[Jarkko Sakkinen]

On Fri, May 29, 2026 at 11:34:06AM +0800, Gui-Dong Han wrote:
> The negative-key race fix added release/acquire ordering for key use.
> 
> Publish payload before state; read state before payload.
> 
> keyring_search_iterator() still uses READ_ONCE() before match callbacks.
> An asymmetric match callback calls asymmetric_key_ids(), which reads
> key->payload.data[asym_key_ids].
> 
> Use key_read_state() there to complete that ordering.

OK, so... I'm having a bit trouble understanding the exact concurrency
scenario you're trying to describe despite I think I get the fix itself
i.e. it is not pairing with mark_key_instantiated?

I'm a bit puzzled too why this was not done already in the original
commit despite introducing all the primitives.

> 
> Fixes: 363b02dab09b ("KEYS: Fix race between updating and finding a negative key")
> Signed-off-by: Gui-Dong Han <hanguidong02@xxxxxxxxx>
> ---
> Found by auditing READ_ONCE() used for synchronization.
> A similar fix can be found in 8df672bfe3ec.
> ---
>  security/keys/keyring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/keys/keyring.c b/security/keys/keyring.c
> index b39038f7dd31..243fb1636f10 100644
> --- a/security/keys/keyring.c
> +++ b/security/keys/keyring.c
> @@ -576,7 +576,7 @@ static int keyring_search_iterator(const void *object, void *iterator_data)
>  	struct keyring_search_context *ctx = iterator_data;
>  	const struct key *key = keyring_ptr_to_key(object);
>  	unsigned long kflags = READ_ONCE(key->flags);
> -	short state = READ_ONCE(key->state);
> +	short state = key_read_state(key);
>  
>  	kenter("{%d}", key->serial);
>  
> -- 
> 2.34.1
> 

BR, Jarkko