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 7E6D8359A81; Sat, 10 Oct 2026 20:50:46 +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=1791665447; cv=none; b=r/wER/q61OlA7rQmp6yoW4/yv2l72tGN3k+rh7dQg/Q6fpDGc2vXfll75YV80+zuTShuXvyQlNwpBM90gwJ/AUG/2e6fd2NcVOuP1JdiYqtMxlpMXph/bIdO3e95QEy9kDN/DZHbBb6c0CBuVF+LRvLMCH51SejoElEDF1pemQE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791665447; c=relaxed/simple; bh=rmVAilQeWkl5we9LBhjSiRFgWd6NY0cKWQ0ZYZHFwa4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=R2kcnzsQeYF7P7bwmFnWOIjuS6ouIPvLl0RwjcCQXC/DmCFsgIgVo9c3T2u4OTtjMwygZ7RbA23A84gfIaQSfw6OaK3DbarS3SEjQh1IFVmA6gL9RYS774Wp94FvEjtJlqY4aHHnQw//AV5bgtZgXxYbXgjJklGiVR44kPYOF+w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Akl7m70R; 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="Akl7m70R" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id 9652C1F000FF; Sat, 10 Oct 2026 20:50:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791665446; bh=X0Q45XJ4iggMQCr/4N98LuVD5wDJk4kXpIcHEMRsaWQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Akl7m70RmTXTcMnrP3KwETYDNh5Rboo51U1QZ5eQYSHe0vUr3E4YlyAzDpc/ZmDiU fDUy6LdruKbc3t/LZLmgIgTK0o7iLT3S1TJY1Y+IL1tjinMf2PsOB0H8H/reLlD8gA 1F/nE9on5Hm5jHAzpd5lkb0MVjT3h2a+s6iILdd7rnb0bfevxIwMhfJHMKZGt/6bTr wPVnkGLWc6isXlnJUu+44+spE+QrztF2MsgFD/gpG0lPxOv8+tImnvP+opTfGKkTOo Fbr+xx72fbNL74hNQK9LuwQLhTAkdvhkJurpTuZcQ32c0k5MUmD5F9oY5K/NHPqA8J m+HkA5S953oFg== Date: Sat, 10 Oct 2026 23:50:42 +0300 From: Jarkko Sakkinen To: Cen Zhang Cc: dhowells@redhat.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, sergeh@kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, jjzuming@gmail.com Subject: Re: [PATCH v2] keys: Avoid the owner account dereference in named keyring lookup Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@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: On Fri, Oct 09, 2026 at 01:11:59PM +0800, Cen Zhang wrote: > 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 > > Fixes: 2ea190d0a006 ("keys: skip keys from another user namespace") > Assisted-by: LLM > Signed-off-by: Cen Zhang > --- > Changes in v2: > - Trim the KASAN report to its two-line fault summary. > > Link to v1: https://lore.kernel.org/r/pm-key-management-objects-candidate-0002-v2-dd6c20a1d92928b33ab7@gmail.com > > diff --git a/security/keys/keyring.c b/security/keys/keyring.c > index 15bf4af8f28218ec3f12c97630d1c76939af7eca..46f774be72967a9bd16b0ddfdf323eda36edeff4 100644 > --- a/security/keys/keyring.c > +++ b/security/keys/keyring.c > @@ -1158,7 +1158,7 @@ struct key *find_keyring_by_name(const char *name, bool uid_keyring) > * 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)) Thanks. Reviewed-by: Jarkko Sakkinen Br, Jarkko