From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FCC8C4338F for ; Sat, 21 Aug 2021 14:13:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DA8B6120F for ; Sat, 21 Aug 2021 14:13:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230061AbhHUOO1 (ORCPT ); Sat, 21 Aug 2021 10:14:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:42520 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229714AbhHUOO1 (ORCPT ); Sat, 21 Aug 2021 10:14:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 97EDB6115A; Sat, 21 Aug 2021 14:10:16 +0000 (UTC) Date: Sat, 21 Aug 2021 16:10:13 +0200 From: Christian Brauner To: Namjae Jeon Cc: Namjae Jeon , Steve French , Christian Brauner , Sergey Senozhatsky , David Sterba , Christoph Hellwig , Hyunchul Lee , linux-cifs@vger.kernel.org Subject: Re: [PATCH] ksmbd: fix lookup on idmapped mounts Message-ID: <20210821141013.n7sg7r2j37fiin5k@wittgenstein> References: <20210816115605.178441-1-brauner@kernel.org> <008d01d792f6$c2735f30$475a1d90$@samsung.com> <20210818174539.ro2ryrbku3ozdjvi@wittgenstein> <000001d794a0$94ec20a0$bec461e0$@samsung.com> <20210819130136.zziq7yr4htiowb5n@wittgenstein> <20210821111117.ngkyc5n6vplayrhx@wittgenstein> <20210821113948.nxzdktqnw36vsyhb@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org On Sat, Aug 21, 2021 at 09:09:28PM +0900, Namjae Jeon wrote: > 2021-08-21 20:39 GMT+09:00, Christian Brauner : > > On Sat, Aug 21, 2021 at 01:11:17PM +0200, Christian Brauner wrote: > >> On Sat, Aug 21, 2021 at 02:59:21PM +0900, Namjae Jeon wrote: > >> > 2021-08-19 22:01 GMT+09:00, Christian Brauner > >> > : > >> > > On Thu, Aug 19, 2021 at 11:19:04AM +0900, Namjae Jeon wrote: > >> > >> > On Tue, Aug 17, 2021 at 08:30:55AM +0900, Namjae Jeon wrote: > >> > >> > > > From: Christian Brauner > >> > >> > > > > >> > >> > > > It's great that the new in-kernel ksmbd server will support > >> > >> > > > idmapped > >> > >> > > > mounts out of the box! However, lookup is currently broken. > >> > >> > > > Lookup > >> > >> > > > helpers such as lookup_one_len() call inode_permission() > >> > >> > > > internally > >> > >> > > > to ensure that the caller is privileged over the inode of the > >> > >> > > > base > >> > >> > > > dentry they are trying to > >> > >> > lookup under. So the permission checking here is currently wrong. > >> > >> > > > > >> > >> > > > Linux v5.15 will gain a new lookup helper lookup_one() that > >> > >> > > > does > >> > >> > > > take idmappings into account. I've added it as part of my > >> > >> > > > patch > >> > >> > > > series to make btrfs support idmapped mounts. The new helper is > >> > >> > > > in > >> > >> > > > linux- next as part of David's (Sterba) btrfs for-next branch > >> > >> > > > as > >> > >> > > > commit c972214c133b ("namei: add > >> > >> > mapping aware lookup helper"). > >> > >> > > > > >> > >> > > > I've said it before during one of my first reviews: I would > >> > >> > > > very > >> > >> > > > much recommend adding fstests to > >> > >> > [1]. > >> > >> > > > It already seems to have very rudimentary cifs support. There > >> > >> > > > is a > >> > >> > > > completely generic idmapped mount testsuite that supports > >> > >> > > > idmapped > >> > >> > > > mounts. > >> > >> > > > > >> > >> > > > [1]: https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/ > >> > >> > > > Cc: Steve French > >> > >> > > > Cc: Christoph Hellwig > >> > >> > > > Cc: Namjae Jeon > >> > >> > > > Cc: Hyunchul Lee > >> > >> > > > Cc: Sergey Senozhatsky > >> > >> > > > Cc: David Sterba > >> > >> > > > Cc: linux-cifs@vger.kernel.org > >> > >> > > > Signed-off-by: Christian Brauner > >> > >> > > > > >> > >> > > > --- > >> > >> > > Hi Christian, > >> > >> > > > >> > >> > > > I merged David's for-next tree into cifsd-next to test this. I > >> > >> > > > did > >> > >> > > > only compile test this. If someone gives me a clear set of > >> > >> > > > instructions how to test ksmbd on my local machine I can at > >> > >> > > > least > >> > >> > > > try to cut some time out of my week to do more reviews. (I'd > >> > >> > > > especially like to see acl behavior with ksmbd.) > >> > >> > > > >> > >> > > There is "How to run ksmbd" section in patch cover letter. > >> > >> > > > >> > >> > > https://protect2.fireeye.com/v1/url?k=65ecaaf0-3a779239-65ed21bf-0cc47 > >> > >> > > a336fae-53bc47005a1a97a9&q=1&e=e44c9f9f-d7ae-4768-8cc2-8f02d748fc6e&u= > >> > >> > > https%3A%2F%2Flkml.org%2Flkml%2F2021%2F8%2F5%2F54 > >> > >> > > > >> > >> > > Let me know if it doesn't work well even if you try to run it > >> > >> > > with > >> > >> > > this step. > >> > >> > > And We will also check whether your patch work fine. > >> > >> > > > >> > >> > > > > >> > >> > > > One more thing, the tree for ksmbd was very hard to find. I had > >> > >> > > > to > >> > >> > > > do a lot archeology to end up > >> > >> > at: > >> > >> > > > > >> > >> > > > git://git.samba.org/ksmbd.git > >> > >> > > This is also in the patch cover letter. See "Mailing list and > >> > >> > > repositories" section. > >> > >> > > I think that you can use : > >> > >> > > > >> > >> > > https://protect2.fireeye.com/v1/url?k=8af83a5d-d5630294-8af9b112-0cc47 > >> > >> > > a336fae-e471ffbdb93d05b7&q=1&e=e44c9f9f-d7ae-4768-8cc2-8f02d748fc6e&u= > >> > >> > > https%3A%2F%2Fgithub.com%2Fnamjaejeon%2Fsmb3-kernel%2Ftree%2Fksmbd-v7- > >> > >> > > series > >> > >> > > > >> > >> > > > > >> > >> > > > Would be appreciated if this tree could be reflected in > >> > >> > > > MAINTAINERS > >> > >> > > > or somewhere else. The github repos with the broken out > >> > >> > > > patches/module aren't really that helpful. > >> > >> > > Okay, I will add git address of ksmbd in MAINTAINERS on next > >> > >> > > spin. > >> > >> > > > >> > >> > > > > >> > >> > > > Thanks! > >> > >> > > > Christian > >> > >> > > Really thanks for your review and I will apply this patch after > >> > >> > > checking it. > >> > >> > > >> > >> > Thank your for the pointers. > >> > >> > > >> > >> > Ok, so I've been taking the time to look into cifs and ksmbd today. > >> > >> > My > >> > >> > mental model was wrong. There > >> > >> > are two things to consider here: > >> > >> > > >> > >> > 1. server: idmapped mounts with ksmbd > >> > >> > 2. client: idmapped mounts with cifs > >> > >> > > >> > >> > Your patchset adds support for 1. > >> > >> Right. > >> > >> > >> > >> > Let's say I have the following ksmbd config: > >> > >> > > >> > >> > root@f2-vm:~# cat /etc/ksmbd/smb.conf > >> > >> > [global] > >> > >> > netbios name = SMBD > >> > >> > server max protocol = SMB3 > >> > >> > [test] > >> > >> > path = /opt > >> > >> > writeable = yes > >> > >> > comment = TEST > >> > >> > read only = no > >> > >> > > >> > >> > So /opt can be an idmapped mount and ksmb would know how to deal > >> > >> > with > >> > >> > that correctly, i.e. you could > >> > >> > do: > >> > >> > > >> > >> > mount-idmapped --map-mount=b:1000:0:1 /opt /opt > >> > >> > > >> > >> > ksmbd.mountd > >> > >> > > >> > >> > and ksmbd would take the idmapping of /opt into account. > >> > >> Right. > >> > >> > >> > >> > > >> > >> > That however is different from 2. which is cifs itself being > >> > >> > idmappable. > >> > >> Right. > >> > >> > >> > >> > Whether or not that makes sense or is needed will need some > >> > >> > thinking. > >> > >> > > >> > >> > In any case, this has consequences for xfstests and now I > >> > >> > understand > >> > >> > your earlier confusion. In > >> > >> > another mail you pointed out that cifs reports that idmapped mounts > >> > >> > are > >> > >> > not supported. That is correct > >> > >> > insofar as it means 2. is not supported, i.e. you can't do: > >> > >> Right. > >> > >> > >> > >> > > >> > >> > mount -t cifs -o username=foo,password=bar //server/files /mnt > >> > >> > > >> > >> > and then > >> > >> > > >> > >> > mount-idmapped --map-mount=b:1000:0:1 /mnt /mnt > >> > >> > > >> > >> > but that's also not what you want in order to test for ksmbd. What > >> > >> > you > >> > >> > want is to test 1. > >> > >> Right. So we have manually tested it, not xfstests. > >> > >> > >> > >> > > >> > >> > So your test setup would require you to setup an idmapped mount and > >> > >> > have > >> > >> > ksmbd use that which can then > >> > >> > be mounted by a client. > >> > >> > > >> > >> > With your instructions I was at least able to get a ksmb instance > >> > >> > running and be able to mount a > >> > >> > client with -t cifs. All on the same machine, i.e. my server is > >> > >> > localhost. > >> > >> Okay. > >> > >> > >> > >> > > >> > >> > However, I need to dig a bit into the semantics to make better > >> > >> > assertions about what's going on. > >> > >> Okay. And I have applied your patch to ksmbd. > >> > >> > >> > >> > > >> > >> > Are unix extension supported with ksmb? Everytime I try to use > >> > >> > "posix" > >> > >> > as a mount option with mount -t cifs -o //127.0.0.1/test /mnt I > >> > >> > get > >> > >> > "uid=0" and "gid=0" and "noposix". > >> > >> > I do set "unix extensions = yes" in both the samba and ksmbd > >> > >> > smb.conf. > >> > >> With posix mount option, It should work. It worked well before but it > >> > >> is > >> > >> strange now. > >> > >> > >> > >> I'm not sure this is the correct fix, But could you please try to > >> > >> mount > >> > >> with the below change ? > >> > >> > >> > >> diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c > >> > >> index eed59bc1d913..5fd0b0ddcc57 100644 > >> > >> --- a/fs/cifs/fs_context.c > >> > >> +++ b/fs/cifs/fs_context.c > >> > >> @@ -1268,8 +1268,10 @@ static int smb3_fs_context_parse_param(struct > >> > >> fs_context *fc, > >> > >> case Opt_unix: > >> > >> if (result.negated) > >> > >> ctx->linux_ext = 0; > >> > >> - else > >> > >> + else { > >> > >> + ctx->linux_ext = 1; > >> > >> ctx->no_linux_ext = 1; > >> > >> + } > >> > >> break; > >> > >> case Opt_nocase: > >> > >> ctx->nocase = 1; > >> > > > >> > > That stops the bleeding indeed. :) > >> > Okay, sorry for late response. > >> > > I think a slightly nicer fix might be: > >> > > > >> > > diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c > >> > > index eed59bc1d913..424b8dc2232e 100644 > >> > > --- a/fs/cifs/fs_context.c > >> > > +++ b/fs/cifs/fs_context.c > >> > > @@ -1269,7 +1269,8 @@ static int smb3_fs_context_parse_param(struct > >> > > fs_context *fc, > >> > > if (result.negated) > >> > > ctx->linux_ext = 0; > >> > > else > >> > > - ctx->no_linux_ext = 1; > >> > > + ctx->linux_ext = 1; > >> > > + ctx->no_linux_ext = !ctx->linux_ext; > >> > > break; > >> > > case Opt_nocase: > >> > > ctx->nocase = 1; > >> > > > >> > > So with this patch applied I got unix permissions working after all. > >> > > So > >> > > I was able to do some more testing. > >> > Okay. > >> > > > >> > > Just a few questions (independent of idmapped mounts): > >> > > > >> > > 1. Are the "uid=" and "gid=" mount options ignored when "username=" > >> > > is > >> > > specified and "posix" is specified? > >> > > > >> > > It seems that "uid=" and "gid=" have are silently ignored when > >> > > "posix' is set. They are neither used to report file ownership > >> > > under > >> > > the cifs mountpoint nor are they relevant when determining > >> > > ownership > >> > > on disk? > >> > > > >> > > As an example, assume I have added a user "foo" with uid 1000 to > >> > > ksmbd via: > >> > > > >> > > ksmbd.adduser -a foo > >> > > > >> > > And I mounted a share via: > >> > > > >> > > mount -t cifs -o > >> > > username=foo,password=bar,posix,uid=1234,gid=1234,forceuid,forcegid > >> > > //127.0.0.1/test /mnt > >> > > > >> > > i) Ownership in /mnt appears posix-correct, i.e. "uid=" and "gid=" > >> > > have > >> > > no effect on the reported ownership. > >> > > > >> > > ii) Assume I'm logged in as the root user with uid 0. If I create > >> > > file or directory in /mnt it will be owned by user foo, i.e. > >> > > uid > >> > > 1000, i.e., the "uid=1234" and "gid=1234" mount option have > >> > > zero > >> > > effect on the ownership of the files? > >> > > > >> > > 2. Are the "uid=" and "gid=" options ignored for permission checking > >> > > when "posix" is specified? > >> > > > >> > > 3. Am I correct in assuming that there is no mount option that makes > >> > > chown() or chmod() have an actual effect. > >> > That will be an answer for 1,2, 3 question. There are mount options for > >> > this. > >> > 1. modefromsid > >> > 2. idsfromsid > >> > > >> > You can use this mount option and please check it. > >> > >> Thank you! This works and finally I can hit some codepaths I wasn't able > >> to until now. > >> > >> > > > >> > > cifs seems to have support for it but the ksmbd server doesn't > >> > > seem > >> > > to? > >> > No, you need to use mount options for this as I said. > >> > ksmbd have supported it but I found an issue related to chown and have > >> > fixed. > >> > > >> > Could you please check the below git branch (pulled David'tree + ksmbd > >> > fixes) ? > >> > > >> > git clone --branch=for-christian > >> > https://github.com/namjaejeon/smb3-kernel > >> > >> Thanks, I've pulled that branch. > > > > There's two problems in this patch. I'll post and point out here > > quickly, if you don't mind: > Thanks for your reiview! > > > > commit fd7d13c387798cbc3abd68ecc07b2c868c6d96cb > > Author: Namjae Jeon > > Date: Sat Aug 21 14:39:43 2021 +0900 > > > > ksmbd: fix permission check issue on chown and chmod > > > > When commanding chmod and chown on cifs&ksmbd, ksmbd allows it without > > file > > permissions check. There is code to check it in settattr_prepare. > > Instead of setting the inode directly, update the mode and uid/gid > > through notify_change. > > > > Signed-off-by: Namjae Jeon > > Signed-off-by: Steve French > > > > diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c > > index 0131997c2177..d329ea49fa14 100644 > > --- a/fs/ksmbd/smb2pdu.c > > +++ b/fs/ksmbd/smb2pdu.c > > @@ -5861,10 +5861,15 @@ int smb2_set_info(struct ksmbd_work *work) > > break; > > case SMB2_O_INFO_SECURITY: > > ksmbd_debug(SMB, "GOT SMB2_O_INFO_SECURITY\n"); > > + if (ksmbd_override_fsids(work)) { > > + rc = -ENOMEM; > > + goto err_out; > > + } > > rc = smb2_set_info_sec(fp, > > > > le32_to_cpu(req->AdditionalInformation), > > req->Buffer, > > le32_to_cpu(req->BufferLength)); > > + ksmbd_revert_fsids(work); > > break; > > default: > > rc = -EOPNOTSUPP; > > diff --git a/fs/ksmbd/smbacl.c b/fs/ksmbd/smbacl.c > > index 20455d810523..f28af33c0bd5 100644 > > --- a/fs/ksmbd/smbacl.c > > +++ b/fs/ksmbd/smbacl.c > > @@ -1300,6 +1300,7 @@ int set_info_sec(struct ksmbd_conn *conn, struct > > ksmbd_tree_connect *tcon, > > struct smb_fattr fattr = {{0}}; > > struct inode *inode = d_inode(path->dentry); > > struct user_namespace *user_ns = mnt_user_ns(path->mnt); > > + struct iattr newattrs; > > > > fattr.cf_uid = INVALID_UID; > > fattr.cf_gid = INVALID_GID; > > @@ -1309,12 +1310,28 @@ int set_info_sec(struct ksmbd_conn *conn, struct > > ksmbd_tree_connect *tcon, > > if (rc) > > goto out; > > > > - inode->i_mode = (inode->i_mode & ~0777) | (fattr.cf_mode & 0777); > > - if (!uid_eq(fattr.cf_uid, INVALID_UID)) > > - inode->i_uid = fattr.cf_uid; > > - if (!gid_eq(fattr.cf_gid, INVALID_GID)) > > + newattrs.ia_valid = ATTR_CTIME; > > + if (!uid_eq(fattr.cf_uid, INVALID_UID)) { > > + newattrs.ia_valid |= ATTR_UID; > > + newattrs.ia_uid = fattr.cf_uid; > > + } > > + if (!gid_eq(fattr.cf_gid, INVALID_GID)) { > > inode->i_gid = fattr.cf_gid; > > > > This needs to be removed. If setattr_prepare() fails you will still end > > up with inode->i_gid changed, i.e. you're changing group ownership even > > if you fail the subsequent setattr_prepare(). > Oops, My mistake, I am missing remove this line. > > > > - mark_inode_dirty(inode); > > + newattrs.ia_valid |= ATTR_GID; > > + newattrs.ia_gid = fattr.cf_gid; > > + } > > + newattrs.ia_valid |= ATTR_MODE; > > + newattrs.ia_mode = (inode->i_mode & ~0777) | (fattr.cf_mode & > > 0777); > > + rc = setattr_prepare(user_ns, path->dentry, &newattrs); Sorry, I also forgot to mention that you need to remove this too. All of this is handled in the underlying filesystem's ->setattr. So this just needs a notify_change().