From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4116342049; Wed, 29 Jan 2025 14:39:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738161552; cv=none; b=ceNCrHG5qnVNR6+OC3e2qDvNR0UT3PipK4mD8W5Yft7qtAtxryH4iFZsH0ccPVUYkPAAr5UOXXGyw3FGowQshbYbqBAAoLwssmu2QWUH81zRGQ+zlf/Om3ZEste+4A54KQE3mmOjh6GSRzvf/m9NuaXFmiVpK0CIFt6RfZzGffA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738161552; c=relaxed/simple; bh=8oSoujiQvWMZRWE4d+kFdjQtEAuSGGAHWGMoHqRjvnY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ulw2g0huU86isY4jjKM+/yqYgeqPLXL18dzZhHaQbKqBVMO//VzxnaLkjLBFb3bS8v97ZM7D1QObdiiPQ9JRdsALcl5PVgX+NSNymi4ToFWQFhwwhgB839tV/20jRN7G/CtV2jWsLut5mHMz3UjBL+KfwczW1r4hr3qJ80G8LY0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dx5V6ags; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dx5V6ags" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABB80C4CED1; Wed, 29 Jan 2025 14:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738161551; bh=8oSoujiQvWMZRWE4d+kFdjQtEAuSGGAHWGMoHqRjvnY=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=dx5V6agsyZ/cesol9Y3gaLGQj3FOyTpLtfwPrcPPkOAmqO1VkVwVTmGf3K+Eyn58Y j4brYJ0BiaRYb9pwzzlFIWPENGsplfqEV3tvodRTiLLhOer7awjHZqNgmA5iroudmv 6UKI30R/Yp2XaQArWzMnhy4zSY6CpOpXio/jxAeXL6NY9n0ZdvvIKnvx14JggxeV+c BeBsEWkXFNmWF+/8nWh/Gq3p7I/YdC9BxcP16CI5n/Q7PjjZiJQG2jtVFfZO1QehEQ VbYUpgkvUMMG+3tDhOyED0j7ndsk9doO9bLDPr4keYY+5JUleDAgvuw8AwvVuHFWuS Xsdqf3g/M8rwQ== Message-ID: Subject: Re: [PATCH v2 0/7] nfsd: CB_SEQUENCE error handling fixes and cleanups From: Jeff Layton To: Chuck Lever , Neil Brown , Olga Kornievskaia , Dai Ngo , Tom Talpey , "J. Bruce Fields" , Kinglong Mee , Trond Myklebust , Anna Schumaker Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 29 Jan 2025 09:39:09 -0500 In-Reply-To: <2f2c7a8b-d44b-4f41-99db-f3401108198c@oracle.com> References: <20250129-nfsd-6-14-v2-0-2700c92f3e44@kernel.org> <2f2c7a8b-d44b-4f41-99db-f3401108198c@oracle.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ 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CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-01-29 at 09:22 -0500, Chuck Lever wrote: > On 1/29/25 8:39 AM, Jeff Layton wrote: > > While looking over the CB_SEQUENCE error handling, I discovered that > > callbacks don't hold a reference to a session, and the > > clp->cl_cb_session could easily change between request and response. > > If that happens at an inopportune time, there could be UAFs or weird > > slot/sequence handling problems. > >=20 > > This series changes the nfsd4_session to be RCU-freed, and then adds a > > new method of session refcounting that is compatible with the old. > > nfsd4_callback RPCs will now hold a lightweight reference to the sessio= n > > in addition to the slot. Then, all of the callback handling is switched > > to use that session instead of dereferencing clp->cb_cb_session. > > I've also reworked the error handling in nfsd4_cb_sequence_done() > > based on review comments, and lifted the v4.0 handing out of that > > function. > >=20 > > This passes pynfs, nfstests, and fstests for me, but I'm not sure how > > much any of that stresses the backchannel's error handling. > >=20 > > These should probably go in via Chuck's tree, but the last patch touche= s > > some NFS cnd sunrpc client code, so it'd be good to have R-b's or A-b's > > from Trond and/or Anna on that one. >=20 > A few initial reactions as I get to know this new revision. >=20 > - I have no objection to 7/7, but it does seem a bit out of place in > this series. Maybe hold it back and send it separately after this > series goes in? >=20 > - The fact that the session can be replaced while a callback operation > is pending suggests that, IIUC, decode_cb_sequence() sanity checking > will fail in such cases, and it's not because of a bug in the client's > callback server. Or maybe I'm overthinking it - that is exactly what > you are trying to prevent? >=20 That's the best-case scenario, but callbacks can run at any time. If this happens at the wrong time this could crash or cause more subtle problems than just a spurious ESERVERFAULT. IOW, we could pass decode_cb_sequence(), then the pointer changes and then nfsd4_cb_sequence_done() ends up working with a different session. > - In 1/7, the kdoc comment for "get" should enumerate the return values > and their meanings. >=20 Ack > - cb_session_changed =3D> nfsd4_cb_session_changed. >=20 Ack > - I'm still not convinced it's wise to bump the slot number in the > ESERVERFAULT case. >=20 It's debatable for sure. The client _did_ respond with NFS4_OK in this case, but it is a bit sketchy since something else didn't match. I'm fine with removing that seq bump if you prefer. > - IMO the cb_sequence_done rework should rename "need_restart" to > "need_requeue" or just "requeue" -- there is a call to > rpc_restart_call_prepare() here that is a little confusing and > could do with some disambiguation. >=20 Good point. I'll change that too. Thanks for the review! >=20 > > Signed-off-by: Jeff Layton > > --- > > Changes in v2: > > - make nfsd4_session be RCU-freed > > - change code to keep reference to session over callback RPCs > > - rework error handling in nfsd4_cb_sequence_done() > > - move NFSv4.0 handling out of nfsd4_cb_sequence_done() > > - Link to v1: https://lore.kernel.org/r/20250123-nfsd-6-14-v1-0-c1137a4= fa2ae@kernel.org > >=20 > > --- > > Jeff Layton (7): > > nfsd: add routines to get/put session references for callbacks > > nfsd: make clp->cl_cb_session be an RCU managed pointer > > nfsd: add a cb_ses pointer to nfsd4_callback and use it instead = of clp->cb_cb_session > > nfsd: overhaul CB_SEQUENCE error handling > > nfsd: remove unneeded forward declaration of nfsd4_mark_cb_fault= () > > nfsd: lift NFSv4.0 handling out of nfsd4_cb_sequence_done() > > sunrpc: make rpc_restart_call() and rpc_restart_call_prepare() v= oid return > >=20 > > fs/nfs/nfs4proc.c | 12 ++- > > fs/nfsd/nfs4callback.c | 212 ++++++++++++++++++++++++++++++++---= --------- > > fs/nfsd/nfs4state.c | 43 ++++++++- > > fs/nfsd/state.h | 6 +- > > fs/nfsd/trace.h | 6 +- > > include/linux/sunrpc/clnt.h | 4 +- > > net/sunrpc/clnt.c | 7 +- > > 7 files changed, 210 insertions(+), 80 deletions(-) > > --- > > base-commit: a05af3c6103b703d1d38d8180b3ebbe0a03c2f07 > > change-id: 20250123-nfsd-6-14-b0797e385dc0 > >=20 > > Best regards, >=20 >=20 --=20 Jeff Layton