From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2BAC0199920 for ; Thu, 2 Jul 2026 15:11:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783005074; cv=none; b=L6ohMA29QLvtUw0iM9vbwnoCTb5lY07dODLFlOeHvABfHIy7uR7wSciCWBo5R4fPm3Vo+NPygYGQ2B+sUgh+4Woagep19UqexCOLEAqQZYZhw7XMZE3FMhyQ5dnCGv9oDv3xuNqVnyAXiLzjpNh748erRTsSPP8xZWCN6c0kHI8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783005074; c=relaxed/simple; bh=rxA2g75mZ2zg4WRZA/M0wg/BD4vaXQZyz0JOAv3FOk8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=X1V5XTt8U0VSC/iqXklI+yHwRPkTNI/T2kACD/xT387jM0JpMxrmjmZYQuiOZ5JuckmVqeBWa+4asuYoyB3w9eyJr7xkhYrs/6ZjLyqXZewDg7xIOJY459WA/gdrqzvCY9p6wGjRk/dVNaZ/9YXa+mDzi7NLfzXBB86nZzKW/3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aXJ0GY+C; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aXJ0GY+C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67D511F000E9; Thu, 2 Jul 2026 15:11:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783005073; bh=GVV0eXw6QGhbOUwbf2ycu3cMPbwOpommhUQ8YFYOKII=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aXJ0GY+CcKX6uk6jnF7vTTBvFB6q9ocnE6ZL24e+lmcKR82ZCcIgKQ2mgbvlt0nZ7 aIaElOg+rD0vRuX1zUQLgyrpXpMod1r6tMWCD/Od1xjfNudfZ5IkzqbbEdYSlkRMvQ S3SIYX+D6/srKCRikKXn+oV6FcffC01LO1qrlcA6xFvYg7zjGfnQ8Q2cQNHlca7jyE oXInUtWd+7Kjmotc+beoMObYPzeJDmbBVZEkSBUkDMH+vqUDA3X82CZ0DjYseUBa+r sEgcUQAzGo+HJMmLCCgERgOls0zbai7TGwOAx6lIwVW/+ThXDGHNXZyzAlSr5oUpL/ GeYCT/KWM3UEw== From: Sasha Levin To: stable@vger.kernel.org Cc: Ruslan Valiyev , Colin Ian King , John Johansen , Sasha Levin Subject: [PATCH 5.15.y] apparmor: fix use-after-free in rawdata dedup loop Date: Thu, 2 Jul 2026 11:11:10 -0400 Message-ID: <20260702151110.3513223-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026070220-ditto-skinny-d644@gregkh> References: <2026070220-ditto-skinny-d644@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ruslan Valiyev [ Upstream commit 6f060496d03e4dc560a40f73770bd08335cb7a27 ] aa_replace_profiles() walks ns->rawdata_list to dedup the incoming policy blob against entries already attached to existing profiles. Per the kernel-doc on struct aa_loaddata, list membership does not hold a reference: profiles hold pcount, and when the last pcount drops, do_ploaddata_rmfs() is queued on a workqueue that takes ns->lock and removes the entry. Between dropping the last pcount and the workqueue running, an entry remains on the list with pcount == 0. aa_get_profile_loaddata() is an unconditional kref_get() on pcount, so when the dedup loop hits such an entry, refcount hardening reports refcount_t: addition on 0; use-after-free. inside aa_replace_profiles(), and the poisoned counter then trips "saturated" and "underflow" warnings on the subsequent uses of the same loaddata. Before commit a0b7091c4de4 ("apparmor: fix race on rawdata dereference") the dedup path used a get_unless_zero-style helper on a single counter, so the existing "if (tmp)" guard was meaningful. The split-refcount refactor introduced aa_get_profile_loaddata(), which has plain kref_get() semantics, and the guard quietly became a no-op. Introduce aa_get_profile_loaddata_not0(), matching the existing _not0 convention used by aa_get_profile_not0(), and use it for the rawdata_list dedup lookup so dying entries are skipped. Reproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu 24.04 + stress-ng 0.17.06: stress-ng --apparmor 1 --klog-check --timeout 60s Without this patch the three refcount_t warnings fire within a few seconds. With it the same 60 s run is clean. Coverage is a smoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN and CONFIG_PROVE_LOCKING would be welcome from anyone with the cycles. Fixes: a0b7091c4de4 ("apparmor: fix race on rawdata dereference") Reported-by: Colin Ian King Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221513 Cc: stable@vger.kernel.org Signed-off-by: Ruslan Valiyev Signed-off-by: John Johansen Signed-off-by: Sasha Levin --- security/apparmor/include/policy_unpack.h | 19 +++++++++++++++++++ security/apparmor/policy.c | 8 ++++++-- 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/security/apparmor/include/policy_unpack.h b/security/apparmor/include/policy_unpack.h index 61cc9b5b8a1f36..b6af40885860b4 100644 --- a/security/apparmor/include/policy_unpack.h +++ b/security/apparmor/include/policy_unpack.h @@ -122,6 +122,25 @@ aa_get_profile_loaddata(struct aa_loaddata *data) return data; } +/** + * aa_get_profile_loaddata_not0 - get a profile reference count if not zero + * @data: reference to get a count on + * + * Like aa_get_profile_loaddata(), but safe to call on an entry that may + * be on a list (e.g. ns->rawdata_list) where the last pcount has already + * dropped and the deferred cleanup has not yet run. + * + * Returns: pointer to reference, or %NULL if @data is NULL or its + * profile refcount has already reached zero. + */ +static inline struct aa_loaddata * +aa_get_profile_loaddata_not0(struct aa_loaddata *data) +{ + if (data && kref_get_unless_zero(&data->pcount)) + return data; + return NULL; +} + void __aa_loaddata_update(struct aa_loaddata *data, long revision); bool aa_rawdata_eq(struct aa_loaddata *l, struct aa_loaddata *r); void aa_loaddata_kref(struct kref *kref); diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c index 62ac50db5f803e..46d84d3a099866 100644 --- a/security/apparmor/policy.c +++ b/security/apparmor/policy.c @@ -976,8 +976,12 @@ ssize_t aa_replace_profiles(struct aa_ns *policy_ns, struct aa_label *label, if (aa_rawdata_eq(rawdata_ent, udata)) { struct aa_loaddata *tmp; - tmp = aa_get_profile_loaddata(rawdata_ent); - /* check we didn't fail the race */ + /* + * Entries remain on rawdata_list with + * pcount == 0 until do_ploaddata_rmfs() + * runs; only take a live profile ref. + */ + tmp = aa_get_profile_loaddata_not0(rawdata_ent); if (tmp) { aa_put_profile_loaddata(udata); udata = tmp; -- 2.53.0