From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793831465; b=OriPwc8GDjYQyYY4dmsabsHF2AAdw2/nXJp7gudVdkw/WxiqmmhhgITN3tKd6PesJ+Hu 0wb/KZLa3BYeyFFNJmW6xW/bwefJWRX2Ldp11P9pVaN70P/cmAD6zNuZpnQzHS1wOQz9S 6pf3op5JnqRf349AFitQvwDcYtl7M+hiEcuKMGcnzuveSAf9xo3xL1WWXcfn7ocwwiuC4 b//4l6e9rowiNcewz5H5TgZNVqolUkK/6+/1hI8ij8nV3jofoxkihs6gZiRDTjjUvw4K1 BQ+FOZ16OAFLa8lBVzWmc5hkRcAWVndZLAoIGWzQV2OXyJcDI3/fR+LcZ5rX72AI01Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831465; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=DLu8ONxoKn/q4xS68Dago4mtGglax0zgNlxbycGOdzE=; b=mk4Wv/h2CqAYcknCKxovZFE4ZMIS+/0pvirYOHO6Zj8B4zNy+sVCbX+kVW1CbUoiJLsE IjFgLd+1wSMneIGmkrmfSy9DGiWryluxUoQf9zAzUwnBwOvzU7fVrBjEAqREHrzLhaZPH Sr/5nOWFpKWnRZHbR5lajsKYf+l4FIxoTY4rygjqQu18NPCIC1NDsgZpUbfk+CNCotme5 yraQojvr02NO0ABEIl2IYWKlqIdB6zXnTMANknJrzM6EApeOTl/idBl0KW2mOVXlNmRF9 YbqXgKWHjkt9P+7v7iZE9Fci57bCLb+qovt9ktXDWQNWu8FU2GCGrQKOYNEvG3Q6wuQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=sI0WraRN; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B6D5606A335; Wed, 4 Nov 2026 22:31:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=sI0WraRN Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93BB21F00A02; Wed, 4 Nov 2026 22:31:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831464; bh=DLu8ONxoKn/q4xS68Dago4mtGglax0zgNlxbycGOdzE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=sI0WraRNeBJlm0/v4LaTTZSqhh2Y6SRG1jTvEg7aTrGPXvjx4gJbLd7a5hAehWbfE qMidfFaekAZjHjyynizZVHeQ5P6MyvZ4d0qJLx7EXcmJmY8XS20K9oD76s4lcjekfT 53Wbxh3Oj76P4A6UebACzxfkY4wMxtun8h5u21p0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Binbin Deng <18983559317@163.com>, John Johansen Subject: [PATCH 6.18 0680/1005] apparmor: fix a use-after-free in aa_lookupn_ns() Date: Wed, 4 Nov 2026 16:06:53 -0500 Message-ID: <20261104211102.679042377@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Binbin Deng <18983559317@163.com> commit f292873ceb4bd3a1a0f75f884361cd556e457692 upstream. aa_lookupn_ns() takes a reference on the namespace it finds with aa_get_ns(), which is kref_get() on the reference count that the namespace is released through, without checking whether the namespace is still in use. A concurrent removal of a ":"-prefixed namespace looks the same namespace up and only then takes the parent lock to remove it, so the last reference can be dropped between the lookup and the aa_get_ns() call: the reference count then reports the increment on a zero count and the kernel classifies the following use of the object as a use-after-free. A user with CAP_MAC_ADMIN can trigger this by writing a ":" removal and a ":/" removal to /sys/kernel/security/apparmor/.remove concurrently. refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 at refcount_warn_saturate+0xc0/0xe0, CPU#6 Call Trace: aa_lookupn_ns+0xa9/0xc0 aa_remove_profiles+0x4fb/0x730 ? __kvmalloc_node_noprof+0x219/0x5c0 ? __pfx_aa_remove_profiles+0x10/0x10 ? aa_loaddata_alloc+0x65/0x1f0 ? _copy_from_user+0x2d/0x80 ? aa_loaddata_alloc+0x111/0x1f0 profile_remove+0x2ee/0x4a0 vfs_write+0x21e/0xcf0 ? rcu_core+0x29c/0x1740 ? timerqueue_linked_add+0x1f4/0x3d0 ? __pfx_vfs_write+0x10/0x10 ? mutex_lock+0x81/0xe0 ? __pfx_mutex_lock+0x10/0x10 ? __pfx_rcu_core+0x10/0x10 ? __pfx_hrtimer_update_next_event+0x10/0x10 ? mutex_unlock+0x7b/0xd0 ? fdget_pos+0x24d/0x4b0 ksys_write+0xf7/0x1c0 ? __pfx_ksys_write+0x10/0x10 ? restore_fpregs_from_fpstate+0x37/0xc0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fix by rejecting a namespace whose reference count is zero. Fixes: 3664268f19ea0 ("apparmor: add namespace lookup fns()") Cc: stable@vger.kernel.org Signed-off-by: Binbin Deng <18983559317@163.com> Signed-off-by: John Johansen Signed-off-by: Greg Kroah-Hartman --- security/apparmor/include/policy_ns.h | 16 ++++++++++++++++ security/apparmor/policy_ns.c | 2 +- 2 files changed, 17 insertions(+), 1 deletion(-) --- a/security/apparmor/include/policy_ns.h +++ b/security/apparmor/include/policy_ns.h @@ -118,6 +118,22 @@ static inline struct aa_ns *aa_get_ns(st } /** + * aa_get_ns_not0 - increment references count on @ns found via lookup + * @ns: namespace to increment reference count of (MAYBE NULL) + * + * Returns: pointer to @ns, if @ns is NULL returns NULL, + * NULL if @ns is being freed + * Requires: @ns must be held with valid refcount when called + */ +static inline struct aa_ns *aa_get_ns_not0(struct aa_ns *ns) +{ + if (ns && aa_get_profile_not0(ns->unconfined)) + return ns; + + return NULL; +} + +/** * aa_put_ns - decrement refcount on @ns * @ns: namespace to put reference of * --- a/security/apparmor/policy_ns.c +++ b/security/apparmor/policy_ns.c @@ -207,7 +207,7 @@ struct aa_ns *aa_lookupn_ns(struct aa_ns struct aa_ns *ns = NULL; rcu_read_lock(); - ns = aa_get_ns(__aa_lookupn_ns(view, name, n)); + ns = aa_get_ns_not0(__aa_lookupn_ns(view, name, n)); rcu_read_unlock(); return ns;