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Wed, 19 Mar 2025 12:31:19 -0400 X-MC-Unique: 1Tcnj-kcMDO0qR63P9N4DQ-1 X-Mimecast-MFC-AGG-ID: 1Tcnj-kcMDO0qR63P9N4DQ_1742401877 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 072F11955E90; Wed, 19 Mar 2025 16:31:17 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.226.12]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 01EC31955DCD; Wed, 19 Mar 2025 16:31:12 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 19 Mar 2025 17:30:44 +0100 (CET) Date: Wed, 19 Mar 2025 17:30:39 +0100 From: Oleg Nesterov To: David Howells Cc: Jarkko Sakkinen , Kees Cook , Greg KH , Josh Drake , Suraj Sonawane , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, security@kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] keys: Fix UAF in key_put() Message-ID: <20250319163038.GD26879@redhat.com> References: <2874581.1742399866@warthog.procyon.org.uk> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2874581.1742399866@warthog.procyon.org.uk> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On 03/19, David Howells wrote: > > --- a/security/keys/gc.c > +++ b/security/keys/gc.c > @@ -218,8 +218,10 @@ static void key_garbage_collector(struct work_struct *work) > key = rb_entry(cursor, struct key, serial_node); > cursor = rb_next(cursor); > > - if (refcount_read(&key->usage) == 0) > + if (test_bit(KEY_FLAG_FINAL_PUT, &key->flags)) { > + smp_mb(); /* Clobber key->user after FINAL_PUT seen. */ > goto found_unreferenced_key; > + } > > if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) { > if (key->type == key_gc_dead_keytype) { > diff --git a/security/keys/key.c b/security/keys/key.c > index 3d7d185019d3..7198cd2ac3a3 100644 > --- a/security/keys/key.c > +++ b/security/keys/key.c > @@ -658,6 +658,8 @@ void key_put(struct key *key) > key->user->qnbytes -= key->quotalen; > spin_unlock_irqrestore(&key->user->lock, flags); > } > + smp_mb(); /* key->user before FINAL_PUT set. */ Can't resist, smp_mb__before_atomic() should equally work, but this doesn't really matter, please forget. > + set_bit(KEY_FLAG_FINAL_PUT, &key->flags); > schedule_work(&key_gc_work); I believe this patch is correct, Reviewed-by: Oleg Nesterov