From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.hallyn.com (mail.hallyn.com [178.63.66.53]) (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 876D44DDB37; Thu, 8 Oct 2026 15:26:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.63.66.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791473173; cv=none; b=dN+viY+2OXDvhIG6+gHBi/xZ9jZjAUU7+ulrzA1jcGTGCIYwYn1dMIXaJSCuYctIaEi1A5h49pkkgdj7rMaxM5dCpu6PPoRiSIDICgiXn/a6FUPuZ/z3rSd9yBWLOss1kFShpupQkf8ALf5jet/vYp9652G+SJbcnLAa+ZhvxaU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791473173; c=relaxed/simple; bh=cDyuwEKK8sXGpAj3kWtZyNN+HaU08rNG0W1xctdiPug=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=InwyyYOQ8ZytumyQi30SqnNodGgs3ngItd3S3JtJdeitllY0AoqxoiaOWvoAjKytqap9VbW3CxpiSRXDMkh1gx9CEGgM3Ln1Om0gbTGq9srwmOkZ8tt57uRqbFwGFBEIBQgaHEhOdiB/Dm03fIGYQPMgBGBwH6P5L36rS1wkoPA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=hallyn.com; spf=pass smtp.mailfrom=hallyn.com; dkim=pass (2048-bit key) header.d=hallyn.com header.i=@hallyn.com header.b=f9INlEzW; arc=none smtp.client-ip=178.63.66.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=hallyn.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=hallyn.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=hallyn.com header.i=@hallyn.com header.b="f9INlEzW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hallyn.com; s=mail; t=1791473148; bh=cDyuwEKK8sXGpAj3kWtZyNN+HaU08rNG0W1xctdiPug=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f9INlEzWvRKdr/Fb3T5Ad0Gww3mff6qF274Hh6qjZDcgZoItXuJ/GPwrJbw9NrxCu 47STDsY6pWekjbCUBwrDFdx59pH6kr/RDs/RRMBMtHMZ+LoiWP16LYuBMFomx+Zmuw QP7MhJyvW8BAm7eOcPYT2aZUbTGTbgtdzi86Kcm7lAljvdfM+SQWkdu7Cffkp6nlma uhxKRDvTp1+6vN7KW2xZgC6y/Fk+nciX9qD3LMfa5sUL5ETmVj8kTCeatcIF1eBKFF F5goSCrada9f7KvJar7ESKWMlbK3JPZwgXg/u1GAr41q2gPb3Kp0hmxegSZ5yAEqDx A2JaIXt7uutfw== Received: by mail.hallyn.com (Postfix, from userid 1001) id A5939196B; Thu, 8 Oct 2026 10:25:48 -0500 (CDT) Date: Thu, 8 Oct 2026 10:25:48 -0500 From: "Serge E. Hallyn" To: Jarkko Sakkinen Cc: David Howells , keyrings@vger.kernel.org, Jann Horn , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Paul Moore , James Morris Subject: Re: [RFC PATCH 0/2] keys: Address lookup_user_key() mutability Message-ID: References: <20260924055521.1981957-1-jarkko@kernel.org> Precedence: bulk X-Mailing-List: linux-security-module@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 Thu, Oct 08, 2026 at 05:26:46PM +0300, Jarkko Sakkinen wrote: > On Tue, Oct 06, 2026 at 01:52:28PM -0500, Serge Hallyn (AMD) wrote: > > On Mon, Oct 05, 2026 at 09:46:41PM +0300, Jarkko Sakkinen wrote: > > > On Mon, Oct 05, 2026 at 08:09:24AM -0500, Serge E. Hallyn wrote: > > > > On Sun, Oct 04, 2026 at 08:54:06PM +0300, Jarkko Sakkinen wrote: > > > > > On Thu, Sep 24, 2026 at 08:55:16AM +0300, Jarkko Sakkinen wrote: > > > > > > The main objective in these patches is to remove to unneeded mutability > > > > > > from key look ups. It does harm and brings no value so it is pretty obvious > > > > > > to me that addressing this harmful behaviour is what we should do. > > > > > > > > > > > > I based the first patch on what Jann suggested in [1]. Nothing too clever here > > > > > > and I'm ofc open for further suggestions. > > > > > > > > > > > > [1] https://lore.kernel.org/keyrings/CAG48ez0XjVSR=M--UBauTm8sJuc+ZbhKzaPa3a6wrSVHyoKevw@mail.gmail.com/ > > > > > > > > > > > > Jarkko Sakkinen (2): > > > > > > keys: Return user session keyring on lookup > > > > > > keys: Reject keyring creation with overridden credentials > > > > > > > > > > > > Documentation/security/keys/core.rst | 7 ++- > > > > > > security/keys/process_keys.c | 65 +++++++++++++++------------- > > > > > > 2 files changed, 40 insertions(+), 32 deletions(-) > > > > > > > > > > > > -- > > > > > > 2.47.3 > > > > > > > > > > > > > > > > So.. should I move forward to with non-RFC v2? > > > > > > > > Patch 2 absolutely makes sense, "doc, it hurts when I do this", "don't do > > > > that then." > > > > > > > > Regarding patch 1, that seems like quite a change in behavior, right? I > > > > don't see any docs or comments that promise the current behavior, but > > > > has any userspace or subsystem come to depend on it? I guess that, if so, > > > > then it just has to create a link to the user session keyring like pam > > > > (according to what I've read) does? > > > > > > Thanks a lot of responding. > > > > > > I fully agree with you but I'd need help for evaluating things further. > > > > > > 1/2 based on Jann's email about the topic and my interpretation of the > > > suggestion. I neither used brains nor AI for this and consider the patch > > > merely as a conversation starter (and what a great success it was on doing > > > that) :-) > > > > :) > > > > > All feedback is good feedback at this point. I need supporting code to > > > remember/recall later on so at least this serves that purpose. > > > > > > Br, Jarkko > > > > I've been staring at the before and after code for a bit now. > > It does even more than I was thinking :) But I was trying to > > detail the changed behavior (from userspace's pov), and after > > several attempts, it seems maybe there actually isn't any. > > > > Q: is there any path whereby the > > > > ``` > > else if (test_bit(KEY_FLAG_UID_KEYRING, > > &ctx.cred->session_keyring->flags) && > > lflags & KEY_LOOKUP_CREATE) { > > ``` > > > > case can still happen? Or was this the only place where we installed > > the user_session keyring as session keyring, so that we can drop this > > branch? > > Right, so *I think* that it is not useful and e.g., PAM uses NULL. > > At the same time it is harmless. We could remove it but it would be > also uapi change (for granted, useless branch). There's https://sources.debian.org/src/e2fsprogs/1.47.4-1/misc/e4crypt.c?hl=568#L568 which bemoans that: * The fact that the keyctl system call and the add_key system * call treats KEY_SPEC_SESSION_KEYRING differently when a * session keyring does not exist is very unfortunate and * confusing, but so it goes... Near as I can tell, add_key just always uses KEY_LOOKUP_CREATE? And https://sources.debian.org/src/krb5/1.22.1-3/src/lib/krb5/ccache/cc_keyring.c?hl=307#L307 I'm not sure whether previous kernels did that, or whether the authors mixed up testing with and without KEY_LOOKUP_CREATE. > I could do it but not without any feedback from David. > > Br, Jarkko