linux-kernel - Re: [PATCH] fscrypt: clear keyring before calling key

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Message-ID: <87ttmkaa4d.fsf@suse.de>
Date: Wed, 07 Feb 2024 09:37:06 +0000
From: Luis Henriques <lhenriques@...e.de>
To: Eric Biggers <ebiggers@...nel.org>
Cc: "Theodore Y. Ts'o" <tytso@....edu>,  Jaegeuk Kim <jaegeuk@...nel.org>,
  David Howells <dhowells@...hat.com>,  Jarkko Sakkinen
 <jarkko@...nel.org>,  linux-fscrypt@...r.kernel.org,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fscrypt: clear keyring before calling key_put()

Eric Biggers <ebiggers@...nel.org> writes:

> On Tue, Feb 06, 2024 at 10:16:19AM +0000, Luis Henriques wrote:
>> Now that the key quotas are handled immediately on key_put() instead of
>> being postponed to the key management garbage collection worker, a call to
>> keyring_clear() is all that is required in fscrypt_put_master_key() so that
>> the keyring clean-up is also done synchronously.  This patch should fix the
>> fstest generic/581 flakiness.
>> 
>> Signed-off-by: Luis Henriques <lhenriques@...e.de>
>> ---
>> Hi!
>> 
>> I know that patch "keys: update key quotas in key_put()" isn't yet merged
>> but since David and Jarkko seem to be OK with it, it doesn't hurt to send
>> this follow-up patch immediately.
>> 
>> Cheers,
>> -- 
>> Luis
>> 
>>  fs/crypto/keyring.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)
>> 
>> diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
>> index 0edf0b58daa7..dfdaae16b83a 100644
>> --- a/fs/crypto/keyring.c
>> +++ b/fs/crypto/keyring.c
>> @@ -74,8 +74,11 @@ void fscrypt_put_master_key(struct fscrypt_master_key *mk)
>>  	 * that concurrent keyring lookups can no longer find it.
>>  	 */
>>  	WARN_ON_ONCE(refcount_read(&mk->mk_active_refs) != 0);
>> -	key_put(mk->mk_users);
>> -	mk->mk_users = NULL;
>> +	if (mk->mk_users) {
>> +		keyring_clear(mk->mk_users);
>> +		key_put(mk->mk_users);
>> +		mk->mk_users = NULL;
>> +	}
>>  	call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key);
>
> Applied, thanks.  I added a comment above the call to keyring_clear() to explain
> why it's there:
>
>         /* Clear the keyring so the quota gets released right away. */

Awesome, makes sense.  Thanks a lot, Eric!

Cheers,
-- 
Luís