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=1793211991; b=3ztZoGmM6gk0PAoK4XDardTlaMkMpyiM+A0w2cbGYWdb+YMvp/0uq5qRXH1n6R2zNow8 mAF4payEQFjZOnZJSZsouq/qWKRPrQumzqT7CeqrqzyVIGVPyxLMKMGEE4TJZ8Uby5tFe ARXYhhSIAinhobSC8tVrQoOm6JolDLoGeBezDASnN0KrP3cxMsdmT3u/uN7QExmGonvGW RI/IYTZrOjz2DowB1/gDFvrxMObcst9AzqldXFsKqWDHAaHXm6xg8c9IvxY3HQ2hD5nqm 871yiSmjk9kqoetFmLfyv+ABmADG4tk5xFxOMinT60fJR/6baKzYdfOVkO8gM48LI1A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793211991; 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=arRU94tv5CLElX6wlC1Ee+cVkTixsi55ecRiccZGxTU=; b=nOLs79U5aQR4ywky9BJGUQf+qk2PGN/tk18BAWlIvPbrOfFUmT/FKu1YSVo6K1L49rQW wKI0mFytZNIb56ZfqMt12hzfpyE2MT0GK07W6ywdyXKKjOOm0y3RqEbqyyzWbMEjpsDxN W1WEaJZhyj4IQllibeiRYsM5gyWZmOvq3MM1gUhAuexWAemjHdiTlqtF2g54KfKaOVbJ0 4xvK1NL2RLht+N7/FNLTK8CFsIlO+0aefRWi3OVQiYuXLMQEt2AHCrq+mrvVB2a5Ckzoj x9K13mAZpQ98WcoDeVke8qMx9qdnEgdAYLiJN3RDiO6Z97Q84u51U9951pMtd4T6uvg== 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=EsEiRVCj; 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 92DFF606A31C; Wed, 28 Oct 2026 18:26:31 +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=EsEiRVCj Received: by smtp.kernel.org (Postfix) with ESMTPSA id E24301F01825; Wed, 28 Oct 2026 18:26:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793211991; bh=arRU94tv5CLElX6wlC1Ee+cVkTixsi55ecRiccZGxTU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EsEiRVCjMqnwDo3bgb6Dxd8+kq97dxOFYWn+axUiSLPkGL8VTnFeSyzKKRmlz8C5f 9qGOjFHHXnz8lkPRv5UhArKKHAhKR6fHeUpupJGWoM8nKTXfG4zGbkruEnOZAkOEYX zgv2G5lPt4o6LdhgySy/y76AR8nJZAnX0N8qooxc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Cen Zhang , Jarkko Sakkinen Subject: [PATCH 5.15 562/571] keys: Avoid the owner account dereference in named keyring lookup Date: Wed, 28 Oct 2026 18:01:49 +0100 Message-ID: <20261028170021.368676189@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170008.009143722@linuxfoundation.org> References: <20261028170008.009143722@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cen Zhang commit 51409aaa01f8602552c336009fd22b226b0cdf1d upstream. Named keyring lookup must keep the storage containing the owner UID alive through the namespace mapping check. find_keyring_by_name() reads keyring->user->uid under keyring_name_lock, but that lock protects the keyring's name entry and allocation, not its separate key_user. A named session-keyring join can overlap a privileged KEYCTL_CHOWN on another CPU. If the keyring holds the last reference to its old dynamic key_user and the ownership transfer succeeds, the following ordering is possible: Named join Chown find_keyring_by_name() keyctl_chown_key() read_lock(keyring_name_lock) down_write(key->sem) load old keyring->user replace key->user and key->uid up_write(key->sem) key_put(key) key_user_put(old user): free read old user->uid read_unlock(keyring_name_lock) Chown neither takes keyring_name_lock nor key_session_mutex, so it can free the old account between the pointer load and the UID read. The lookup then reads freed memory even though the keyring itself is alive. Use keyring->uid for the mapping check. key_alloc() initializes this inline owner UID and keyctl_chown_key() updates it on chown. The existing name lock keeps its containing keyring allocated throughout the check, so lookup no longer depends on the account's lifetime. This also matches the owner UID used by the permission check. KASAN report as below: BUG: KASAN: slab-use-after-free in find_keyring_by_name+0x577/0x5d0 Read of size 4 at addr ffff8881128ae2ec by task keycase/500 Cc: stable@vger.kernel.org Fixes: 2ea190d0a006 ("keys: skip keys from another user namespace") Assisted-by: LLM Signed-off-by: Cen Zhang Reviewed-by: Jarkko Sakkinen Link: https://lore.kernel.org/r/pm-key-management-objects-candidate-0002-v3-2baa8cad2bb554364e10@gmail.com Signed-off-by: Jarkko Sakkinen Signed-off-by: Greg Kroah-Hartman --- security/keys/keyring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1158,7 +1158,7 @@ struct key *find_keyring_by_name(const c * grants Search permission and that hasn't been revoked */ list_for_each_entry(keyring, &ns->keyring_name_list, name_link) { - if (!kuid_has_mapping(ns, keyring->user->uid)) + if (!kuid_has_mapping(ns, keyring->uid)) continue; if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))