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Message-ID: <CAEivzxcCe9j13L-0m4pww_dXXdAQ9evRdMorpncJD9d+MW0Osw@mail.gmail.com>
Date: Fri, 4 Aug 2023 09:33:16 +0200
From: Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To: Xiubo Li <xiubli@...hat.com>
Cc: brauner@...nel.org, stgraber@...ntu.com,
linux-fsdevel@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 03/12] ceph: handle idmapped mounts in create_request_message()
On Fri, Aug 4, 2023 at 8:43 AM Aleksandr Mikhalitsyn
<aleksandr.mikhalitsyn@...onical.com> wrote:
>
> On Fri, Aug 4, 2023 at 8:35 AM Aleksandr Mikhalitsyn
> <aleksandr.mikhalitsyn@...onical.com> wrote:
> >
> > On Fri, Aug 4, 2023 at 5:24 AM Xiubo Li <xiubli@...hat.com> wrote:
> > >
> > >
> > > On 8/4/23 10:26, Xiubo Li wrote:
> > > >
> > > > On 8/3/23 21:59, Alexander Mikhalitsyn wrote:
> > > >> From: Christian Brauner <brauner@...nel.org>
> > > >>
> > > >> Inode operations that create a new filesystem object such as ->mknod,
> > > >> ->create, ->mkdir() and others don't take a {g,u}id argument explicitly.
> > > >> Instead the caller's fs{g,u}id is used for the {g,u}id of the new
> > > >> filesystem object.
> > > >>
> > > >> In order to ensure that the correct {g,u}id is used map the caller's
> > > >> fs{g,u}id for creation requests. This doesn't require complex changes.
> > > >> It suffices to pass in the relevant idmapping recorded in the request
> > > >> message. If this request message was triggered from an inode operation
> > > >> that creates filesystem objects it will have passed down the relevant
> > > >> idmaping. If this is a request message that was triggered from an inode
> > > >> operation that doens't need to take idmappings into account the initial
> > > >> idmapping is passed down which is an identity mapping.
> > > >>
> > > >> This change uses a new cephfs protocol extension
> > > >> CEPHFS_FEATURE_HAS_OWNER_UIDGID
> > > >> which adds two new fields (owner_{u,g}id) to the request head structure.
> > > >> So, we need to ensure that MDS supports it otherwise we need to fail
> > > >> any IO that comes through an idmapped mount because we can't process it
> > > >> in a proper way. MDS server without such an extension will use
> > > >> caller_{u,g}id
> > > >> fields to set a new inode owner UID/GID which is incorrect because
> > > >> caller_{u,g}id
> > > >> values are unmapped. At the same time we can't map these fields with an
> > > >> idmapping as it can break UID/GID-based permission checks logic on the
> > > >> MDS side. This problem was described with a lot of details at [1], [2].
> > > >>
> > > >> [1]
> > > >> https://lore.kernel.org/lkml/CAEivzxfw1fHO2TFA4dx3u23ZKK6Q+EThfzuibrhA3RKM=ZOYLg@mail.gmail.com/
> > > >> [2]
> > > >> https://lore.kernel.org/all/20220104140414.155198-3-brauner@kernel.org/
> > > >>
> > > >> https://github.com/ceph/ceph/pull/52575
> > > >> https://tracker.ceph.com/issues/62217
> > > >>
> > > >> Cc: Xiubo Li <xiubli@...hat.com>
> > > >> Cc: Jeff Layton <jlayton@...nel.org>
> > > >> Cc: Ilya Dryomov <idryomov@...il.com>
> > > >> Cc: ceph-devel@...r.kernel.org
> > > >> Co-Developed-by: Alexander Mikhalitsyn
> > > >> <aleksandr.mikhalitsyn@...onical.com>
> > > >> Signed-off-by: Christian Brauner <brauner@...nel.org>
> > > >> Signed-off-by: Alexander Mikhalitsyn
> > > >> <aleksandr.mikhalitsyn@...onical.com>
> > > >> ---
> > > >> v7:
> > > >> - reworked to use two new fields for owner UID/GID
> > > >> (https://github.com/ceph/ceph/pull/52575)
> > > >> v8:
> > > >> - properly handled case when old MDS used with new kernel client
> > > >> ---
> > > >> fs/ceph/mds_client.c | 46 +++++++++++++++++++++++++++++++++---
> > > >> fs/ceph/mds_client.h | 5 +++-
> > > >> include/linux/ceph/ceph_fs.h | 4 +++-
> > > >> 3 files changed, 50 insertions(+), 5 deletions(-)
> > > >>
> > > >> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > > >> index 8829f55103da..7d3106d3b726 100644
> > > >> --- a/fs/ceph/mds_client.c
> > > >> +++ b/fs/ceph/mds_client.c
> > > >> @@ -2902,6 +2902,17 @@ static void encode_mclientrequest_tail(void
> > > >> **p, const struct ceph_mds_request *
> > > >> }
> > > >> }
> > > >> +static inline u16 mds_supported_head_version(struct
> > > >> ceph_mds_session *session)
> > > >> +{
> > > >> + if (!test_bit(CEPHFS_FEATURE_32BITS_RETRY_FWD,
> > > >> &session->s_features))
> > > >> + return 1;
> > > >> +
> > > >> + if (!test_bit(CEPHFS_FEATURE_HAS_OWNER_UIDGID,
> > > >> &session->s_features))
> > > >> + return 2;
> > > >> +
> > > >> + return CEPH_MDS_REQUEST_HEAD_VERSION;
> > > >> +}
> > > >> +
> > > >> static struct ceph_mds_request_head_legacy *
> > > >> find_legacy_request_head(void *p, u64 features)
> > > >> {
> > > >> @@ -2923,6 +2934,7 @@ static struct ceph_msg
> > > >> *create_request_message(struct ceph_mds_session *session,
> > > >> {
> > > >> int mds = session->s_mds;
> > > >> struct ceph_mds_client *mdsc = session->s_mdsc;
> > > >> + struct ceph_client *cl = mdsc->fsc->client;
> > > >> struct ceph_msg *msg;
> > > >> struct ceph_mds_request_head_legacy *lhead;
> > > >> const char *path1 = NULL;
> > > >> @@ -2936,7 +2948,7 @@ static struct ceph_msg
> > > >> *create_request_message(struct ceph_mds_session *session,
> > > >> void *p, *end;
> > > >> int ret;
> > > >> bool legacy = !(session->s_con.peer_features &
> > > >> CEPH_FEATURE_FS_BTIME);
> > > >> - bool old_version = !test_bit(CEPHFS_FEATURE_32BITS_RETRY_FWD,
> > > >> &session->s_features);
> > > >> + u16 request_head_version = mds_supported_head_version(session);
> > > >> ret = set_request_path_attr(mdsc, req->r_inode, req->r_dentry,
> > > >> req->r_parent, req->r_path1, req->r_ino1.ino,
> > > >> @@ -2977,8 +2989,10 @@ static struct ceph_msg
> > > >> *create_request_message(struct ceph_mds_session *session,
> > > >> */
> > > >> if (legacy)
> > > >> len = sizeof(struct ceph_mds_request_head_legacy);
> > > >> - else if (old_version)
> > > >> + else if (request_head_version == 1)
> > > >> len = sizeof(struct ceph_mds_request_head_old);
> > > >> + else if (request_head_version == 2)
> > > >> + len = offsetofend(struct ceph_mds_request_head, ext_num_fwd);
> > > >> else
> > > >> len = sizeof(struct ceph_mds_request_head);
> > > >
> > > > This is not what we suppose to. If we do this again and again when
> > > > adding new members it will make the code very complicated to maintain.
> > > >
> > > > Once the CEPHFS_FEATURE_32BITS_RETRY_FWD has been supported the ceph
> > > > should correctly decode it and if CEPHFS_FEATURE_HAS_OWNER_UIDGID is
> > > > not supported the decoder should skip it directly.
> > > >
> > > > Is the MDS side buggy ? Why you last version didn't work ?
> > > >
> > >
> > > I think the ceph side is buggy. Possibly we should add one new `length`
> > > member in struct `struct ceph_mds_request_head` and just skip the extra
> > > bytes when decoding it.
> >
> > Hm, I think I found something suspicious. In cephfs code we have many
> > places that
> > call the DECODE_FINISH macro, but in our decoder we don't have it.
> >
> > From documentation it follows that DECODE_FINISH purpose is precisely
> > about this problem.
> >
> > What do you think?
>
> Upd: this thing also changes on-wire format and adds field to store length.
> But this will be a massive and incompatible protocol change. I don't think that
> we want to do this in the scope of this task.
https://github.com/ceph/ceph/pull/52575#issuecomment-1665141641
>
> >
> > >
> > > Could you fix it together with your ceph PR ?
> > >
> > > Thanks
> > >
> > > - Xiubo
> > >
> > >
> > > > Thanks
> > > >
> > > > - Xiubo
> > > >
> > > >> @@ -3028,6 +3042,16 @@ static struct ceph_msg
> > > >> *create_request_message(struct ceph_mds_session *session,
> > > >> lhead = find_legacy_request_head(msg->front.iov_base,
> > > >> session->s_con.peer_features);
> > > >> + if ((req->r_mnt_idmap != &nop_mnt_idmap) &&
> > > >> + !test_bit(CEPHFS_FEATURE_HAS_OWNER_UIDGID,
> > > >> &session->s_features)) {
> > > >> + pr_err_ratelimited_client(cl,
> > > >> + "idmapped mount is used and
> > > >> CEPHFS_FEATURE_HAS_OWNER_UIDGID"
> > > >> + " is not supported by MDS. Fail request with -EIO.\n");
> > > >> +
> > > >> + ret = -EIO;
> > > >> + goto out_err;
> > > >> + }
> > > >> +
> > > >> /*
> > > >> * The ceph_mds_request_head_legacy didn't contain a version
> > > >> field, and
> > > >> * one was added when we moved the message version from 3->4.
> > > >> @@ -3035,17 +3059,33 @@ static struct ceph_msg
> > > >> *create_request_message(struct ceph_mds_session *session,
> > > >> if (legacy) {
> > > >> msg->hdr.version = cpu_to_le16(3);
> > > >> p = msg->front.iov_base + sizeof(*lhead);
> > > >> - } else if (old_version) {
> > > >> + } else if (request_head_version == 1) {
> > > >> struct ceph_mds_request_head_old *ohead = msg->front.iov_base;
> > > >> msg->hdr.version = cpu_to_le16(4);
> > > >> ohead->version = cpu_to_le16(1);
> > > >> p = msg->front.iov_base + sizeof(*ohead);
> > > >> + } else if (request_head_version == 2) {
> > > >> + struct ceph_mds_request_head *nhead = msg->front.iov_base;
> > > >> +
> > > >> + msg->hdr.version = cpu_to_le16(6);
> > > >> + nhead->version = cpu_to_le16(2);
> > > >> +
> > > >> + p = msg->front.iov_base + offsetofend(struct
> > > >> ceph_mds_request_head, ext_num_fwd);
> > > >> } else {
> > > >> struct ceph_mds_request_head *nhead = msg->front.iov_base;
> > > >> + kuid_t owner_fsuid;
> > > >> + kgid_t owner_fsgid;
> > > >> msg->hdr.version = cpu_to_le16(6);
> > > >> nhead->version = cpu_to_le16(CEPH_MDS_REQUEST_HEAD_VERSION);
> > > >> +
> > > >> + owner_fsuid = from_vfsuid(req->r_mnt_idmap, &init_user_ns,
> > > >> + VFSUIDT_INIT(req->r_cred->fsuid));
> > > >> + owner_fsgid = from_vfsgid(req->r_mnt_idmap, &init_user_ns,
> > > >> + VFSGIDT_INIT(req->r_cred->fsgid));
> > > >> + nhead->owner_uid = cpu_to_le32(from_kuid(&init_user_ns,
> > > >> owner_fsuid));
> > > >> + nhead->owner_gid = cpu_to_le32(from_kgid(&init_user_ns,
> > > >> owner_fsgid));
> > > >> p = msg->front.iov_base + sizeof(*nhead);
> > > >> }
> > > >> diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
> > > >> index e3bbf3ba8ee8..8f683e8203bd 100644
> > > >> --- a/fs/ceph/mds_client.h
> > > >> +++ b/fs/ceph/mds_client.h
> > > >> @@ -33,8 +33,10 @@ enum ceph_feature_type {
> > > >> CEPHFS_FEATURE_NOTIFY_SESSION_STATE,
> > > >> CEPHFS_FEATURE_OP_GETVXATTR,
> > > >> CEPHFS_FEATURE_32BITS_RETRY_FWD,
> > > >> + CEPHFS_FEATURE_NEW_SNAPREALM_INFO,
> > > >> + CEPHFS_FEATURE_HAS_OWNER_UIDGID,
> > > >> - CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_32BITS_RETRY_FWD,
> > > >> + CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_HAS_OWNER_UIDGID,
> > > >> };
> > > >> #define CEPHFS_FEATURES_CLIENT_SUPPORTED { \
> > > >> @@ -49,6 +51,7 @@ enum ceph_feature_type {
> > > >> CEPHFS_FEATURE_NOTIFY_SESSION_STATE, \
> > > >> CEPHFS_FEATURE_OP_GETVXATTR, \
> > > >> CEPHFS_FEATURE_32BITS_RETRY_FWD, \
> > > >> + CEPHFS_FEATURE_HAS_OWNER_UIDGID, \
> > > >> }
> > > >> /*
> > > >> diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
> > > >> index 5f2301ee88bc..6eb83a51341c 100644
> > > >> --- a/include/linux/ceph/ceph_fs.h
> > > >> +++ b/include/linux/ceph/ceph_fs.h
> > > >> @@ -499,7 +499,7 @@ struct ceph_mds_request_head_legacy {
> > > >> union ceph_mds_request_args args;
> > > >> } __attribute__ ((packed));
> > > >> -#define CEPH_MDS_REQUEST_HEAD_VERSION 2
> > > >> +#define CEPH_MDS_REQUEST_HEAD_VERSION 3
> > > >> struct ceph_mds_request_head_old {
> > > >> __le16 version; /* struct version */
> > > >> @@ -530,6 +530,8 @@ struct ceph_mds_request_head {
> > > >> __le32 ext_num_retry; /* new count retry attempts */
> > > >> __le32 ext_num_fwd; /* new count fwd attempts */
> > > >> +
> > > >> + __le32 owner_uid, owner_gid; /* used for OPs which create
> > > >> inodes */
> > > >> } __attribute__ ((packed));
> > > >> /* cap/lease release record */
> > >
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