From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 962572D0C72; Sat, 26 Sep 2026 04:48:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790398110; cv=none; b=Zv6ifW/43urkquAnhdD7Vxe6MjQ2V1REW/Z5uN/kvBNxnqpvdFl79cteB/ZprCvDWk1wfy48sbwqBmCnCJvm7rXAweAjyI0a8v/LQEQ402De+Myi93TmY37gM8uWAgKwbPBlUqK8TE6THiHm+HSWXNndk5cp9K8RGPbK0FPVUpQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790398110; c=relaxed/simple; bh=Jh4McRuX8VGkuoqjbR/Q7ARz9onvjFUEMsOtQRDshdE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=BP2E3w/sw5OJw8zyWlkNd2A4/YRlu0M483N/L3ONcO+inKl57a/oqA9TAQZz+Js0qPNki+VTSzY14rO1te5GSI5nVC0ScZSz1Qn/lMLjN3jYpZgFPvm2BeVKw1NPn0vJIa9QPn6deHYw/MhLkVM30c49IRUCAAw5H53CwaVkDLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=NW/TqNAi; arc=none smtp.client-ip=220.197.31.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="NW/TqNAi" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=LO G6wlR4WrEhwbx34Joq7X3VgPhzJyeuVOuxLeR/59M=; b=NW/TqNAig5g2+IddH4 cJ9atdBZyHPoBhS/olzwA01s1kh5N66yp98ZqD8Gkf4ytG7UN/KJgCKoV+pvDYt3 c4co9KFHEIF2158mBFbFlDtBRetR4bM3XNeZCY8/tcEeFiwO2F3yWolG+DYL6G4e rDdwKL64xjbIWntbWQ0CXZj6c= Received: from colol4bi5.localdomain (unknown []) by gzga-smtp-mtada-g0-3 (Coremail) with SMTP id _____wDHv9dnTrdqpZecAw--.19236S2; Sat, 26 Sep 2026 12:47:36 +0800 (CST) From: Binbin Deng <18983559317@163.com> To: john.johansen@canonical.com, georgia.garcia@canonical.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com Cc: ryan.lee@canonical.com, cengiz.can@canonical.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Binbin Deng <18983559317@163.com> Subject: [PATCH security v1] apparmor: fix a use-after-free in aa_lookupn_ns() Date: Sat, 26 Sep 2026 12:47:24 +0800 Message-ID: <20260926044724.4187-1-18983559317@163.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wDHv9dnTrdqpZecAw--.19236S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxAF1DKw4xuF47KF45GF1DAwb_yoW5tr48pF 4fK345CrWkGFy7Zr47W3W3Wr1Y9ayrWr13t393WF4YvFW3Wr48Cr1UtF129ry5CF97AFy0 qa12gw4rZFyDXaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0zRW7K3UUUUU= X-CM-SenderInfo: jprymmytvvmjmrxbiqqrwthudrp/xtbC+wg2Gmq3TmjXFwAA3k 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. Fixes: 3664268f19ea0 ("apparmor: add namespace lookup fns()") Signed-off-by: Binbin Deng <18983559317@163.com> --- security/apparmor/include/policy_ns.h | 16 ++++++++++++++++ security/apparmor/policy_ns.c | 2 +- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/security/apparmor/include/policy_ns.h b/security/apparmor/include/policy_ns.h index cc6e84151812..4f8359875476 100644 --- a/security/apparmor/include/policy_ns.h +++ b/security/apparmor/include/policy_ns.h @@ -117,6 +117,22 @@ static inline struct aa_ns *aa_get_ns(struct aa_ns *ns) return ns; } +/** + * 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 diff --git a/security/apparmor/policy_ns.c b/security/apparmor/policy_ns.c index 5a907a875d8f..ae9168c1a85e 100644 --- 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 *view, const char *name, size_t n) 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; -- 2.43.0