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Tue, 18 Mar 2025 07:23:25 -0400 X-MC-Unique: OS6Qmz25P1KEqEQ641Rh1A-1 X-Mimecast-MFC-AGG-ID: OS6Qmz25P1KEqEQ641Rh1A_1742297003 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 971AF1800266; Tue, 18 Mar 2025 11:23:23 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.44.32.255]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 90BDB180175C; Tue, 18 Mar 2025 11:23:19 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 18 Mar 2025 12:22:51 +0100 (CET) Date: Tue, 18 Mar 2025 12:22:46 +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] keys: Fix UAF in key_put() Message-ID: <20250318112245.GA14792@redhat.com> References: <2477454.1742292885@warthog.procyon.org.uk> Precedence: bulk X-Mailing-List: stable@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: <2477454.1742292885@warthog.procyon.org.uk> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On 03/18, David Howells wrote: > > --- a/security/keys/key.c > +++ b/security/keys/key.c > @@ -645,21 +645,30 @@ EXPORT_SYMBOL(key_reject_and_link); > */ > void key_put(struct key *key) > { > + int quota_flag; > + unsigned short len; > + struct key_user *user; > + > if (key) { > key_check(key); > > + quota_flag = test_bit(KEY_FLAG_IN_QUOTA, &key->flags); > + len = key->quotalen; > + user = key->user; > + refcount_inc(&user->usage); > if (refcount_dec_and_test(&key->usage)) { > unsigned long flags; > > /* deal with the user's key tracking and quota */ > - if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) { > - spin_lock_irqsave(&key->user->lock, flags); > - key->user->qnkeys--; > - key->user->qnbytes -= key->quotalen; > - spin_unlock_irqrestore(&key->user->lock, flags); > + if (quota_flag) { > + spin_lock_irqsave(&user->lock, flags); > + user->qnkeys--; > + user->qnbytes -= len; > + spin_unlock_irqrestore(&user->lock, flags); > } > schedule_work(&key_gc_work); > } > + key_user_put(user); Do we really need the unconditional refcount_inc / key_user_put ? void key_put(struct key *key) { if (key) { struct key_user *user = NULL; unsigned short len; key_check(key); if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) { len = key->quotalen; user = key->user; refcount_inc(&user->usage); } if (refcount_dec_and_test(&key->usage)) { unsigned long flags; /* deal with the user's key tracking and quota */ if (user) { spin_lock_irqsave(&user->lock, flags); user->qnkeys--; user->qnbytes -= len; spin_unlock_irqrestore(&user->lock, flags); } schedule_work(&key_gc_work); } if (user) key_user_put(user); } } looks a bit more clear/simple to me... Oleg.