Re: [PATCH v2] nfsd: inherit required unset default acls from effective set

From: Chuck Lever
Date: Mon Jul 24 2023 - 10:04:05 EST

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In reply to: Jeff Layton: "Re: [PATCH v2] nfsd: inherit required unset default acls from effective set"
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On Mon, Jul 24, 2023 at 09:54:22AM -0400, Jeff Layton wrote:
> On Mon, 2023-07-24 at 09:44 -0400, Chuck Lever wrote:
> > On Mon, Jul 24, 2023 at 08:13:05AM -0400, Jeff Layton wrote:
> > > A well-formed NFSv4 ACL will always contain OWNER@/GROUP@/EVERYONE@
> > > ACEs, but there is no requirement for inheritable entries for those
> > > entities. POSIX ACLs must always have owner/group/other entries, even for a
> > > default ACL.
> > >
> > > nfsd builds the default ACL from inheritable ACEs, but the current code
> > > just leaves any unspecified ACEs zeroed out. The result is that adding a
> > > default user or group ACE to an inode can leave it with unwanted deny
> > > entries.
> > >
> > > For instance, a newly created directory with no acl will look something
> > > like this:
> > >
> > > # NFSv4 translation by server
> > > A::OWNER@:rwaDxtTcCy
> > > A::GROUP@:rxtcy
> > > A::EVERYONE@:rxtcy
> > >
> > > # POSIX ACL of underlying file
> > > user::rwx
> > > group::r-x
> > > other::r-x
> > >
> > > ...if I then add new v4 ACE:
> > >
> > > nfs4_setfacl -a A:fd:1000:rwx /mnt/local/test
> > >
> > > ...I end up with a result like this today:
> > >
> > > user::rwx
> > > user:1000:rwx
> > > group::r-x
> > > mask::rwx
> > > other::r-x
> > > default:user::---
> > > default:user:1000:rwx
> > > default:group::---
> > > default:mask::rwx
> > > default:other::---
> > >
> > > A::OWNER@:rwaDxtTcCy
> > > A::1000:rwaDxtcy
> > > A::GROUP@:rxtcy
> > > A::EVERYONE@:rxtcy
> > > D:fdi:OWNER@:rwaDx
> > > A:fdi:OWNER@:tTcCy
> > > A:fdi:1000:rwaDxtcy
> > > A:fdi:GROUP@:tcy
> > > A:fdi:EVERYONE@:tcy
> > >
> > > ...which is not at all expected. Adding a single inheritable allow ACE
> > > should not result in everyone else losing access.
> > >
> > > The setfacl command solves a silimar issue by copying owner/group/other
> > > entries from the effective ACL when none of them are set:
> > >
> > > "If a Default ACL entry is created, and the Default ACL contains no
> > > owner, owning group, or others entry, a copy of the ACL owner,
> > > owning group, or others entry is added to the Default ACL.
> > >
> > > Having nfsd do the same provides a more sane result (with no deny ACEs
> > > in the resulting set):
> > >
> > > user::rwx
> > > user:1000:rwx
> > > group::r-x
> > > mask::rwx
> > > other::r-x
> > > default:user::rwx
> > > default:user:1000:rwx
> > > default:group::r-x
> > > default:mask::rwx
> > > default:other::r-x
> > >
> > > A::OWNER@:rwaDxtTcCy
> > > A::1000:rwaDxtcy
> > > A::GROUP@:rxtcy
> > > A::EVERYONE@:rxtcy
> > > A:fdi:OWNER@:rwaDxtTcCy
> > > A:fdi:1000:rwaDxtcy
> > > A:fdi:GROUP@:rxtcy
> > > A:fdi:EVERYONE@:rxtcy
> > >
> > > Reported-by: Ondrej Valousek <ondrej.valousek@xxxxxxxxxxx>
> > > Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2136452
> > > Suggested-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > ---
> > > Changes in v2:
> > > - always set missing ACEs whenever default ACL has any ACEs that are
> > > explicitly set. This better conforms to how setfacl works.
> > > - drop now-unneeded "empty" boolean
> > > - Link to v1: https://lore.kernel.org/r/20230719-nfsd-acl-v1-1-eb0faf3d2917@xxxxxxxxxx
> > > ---
> > > fs/nfsd/nfs4acl.c | 32 ++++++++++++++++++++++++++++----
> > > 1 file changed, 28 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
> > > index 518203821790..b931d4383517 100644
> > > --- a/fs/nfsd/nfs4acl.c
> > > +++ b/fs/nfsd/nfs4acl.c
> > > @@ -441,7 +441,7 @@ struct posix_ace_state_array {
> > > * calculated so far: */
> > >
> > > struct posix_acl_state {
> > > - int empty;
> > > + unsigned char valid;
> > > struct posix_ace_state owner;
> > > struct posix_ace_state group;
> > > struct posix_ace_state other;
> > > @@ -457,7 +457,6 @@ init_state(struct posix_acl_state *state, int cnt)
> > > int alloc;
> > >
> > > memset(state, 0, sizeof(struct posix_acl_state));
> > > - state->empty = 1;
> > > /*
> > > * In the worst case, each individual acl could be for a distinct
> > > * named user or group, but we don't know which, so we allocate
> > > @@ -500,7 +499,7 @@ posix_state_to_acl(struct posix_acl_state *state, unsigned int flags)
> > > * and effective cases: when there are no inheritable ACEs,
> > > * calls ->set_acl with a NULL ACL structure.
> > > */
> > > - if (state->empty && (flags & NFS4_ACL_TYPE_DEFAULT))
> > > + if (!state->valid && (flags & NFS4_ACL_TYPE_DEFAULT))
> > > return NULL;
> > >
> > > /*
> > > @@ -622,9 +621,10 @@ static void process_one_v4_ace(struct posix_acl_state *state,
> > > struct nfs4_ace *ace)
> > > {
> > > u32 mask = ace->access_mask;
> > > + short type = ace2type(ace);
> > > int i;
> > >
> > > - state->empty = 0;
> > > + state->valid |= type;
> > >
> > > switch (ace2type(ace)) {
> >
> > Mechanical issue: the patch adds @type, but uses it just once.
> > The switch here also wants the value of ace2type(ace).
> >
> >
>
> Doh! I had that fixed in one version of the patch, but had to rework the
> branch and lost that delta. I can respin, or if you just want to fix
> that in place, then that would be fine too.

I've fixed it in my tree and applied it to nfsd-next. Let me know if
I've done something wrong.

> > > case ACL_USER_OBJ:
> > > @@ -726,6 +726,30 @@ static int nfs4_acl_nfsv4_to_posix(struct nfs4_acl *acl,
> > > if (!(ace->flag & NFS4_ACE_INHERIT_ONLY_ACE))
> > > process_one_v4_ace(&effective_acl_state, ace);
> > > }
> > > +
> > > + /*
> > > + * At this point, the default ACL may have zeroed-out entries for owner,
> > > + * group and other. That usually results in a non-sensical resulting ACL
> > > + * that denies all access except to any ACE that was explicitly added.
> > > + *
> > > + * The setfacl command solves a similar problem with this logic:
> > > + *
> > > + * "If a Default ACL entry is created, and the Default ACL contains
> > > + * no owner, owning group, or others entry, a copy of the ACL
> > > + * owner, owning group, or others entry is added to the Default ACL."
> > > + *
> > > + * Copy any missing ACEs from the effective set, if any ACEs were
> > > + * explicitly set.
> > > + */
> > > + if (default_acl_state.valid) {
> > > + if (!(default_acl_state.valid & ACL_USER_OBJ))
> > > + default_acl_state.owner = effective_acl_state.owner;
> > > + if (!(default_acl_state.valid & ACL_GROUP_OBJ))
> > > + default_acl_state.group = effective_acl_state.group;
> > > + if (!(default_acl_state.valid & ACL_OTHER))
> > > + default_acl_state.other = effective_acl_state.other;
> > > + }
> > > +
> > > *pacl = posix_state_to_acl(&effective_acl_state, flags);
> > > if (IS_ERR(*pacl)) {
> > > ret = PTR_ERR(*pacl);
> > >
> > > ---
> > > base-commit: 7bfb36a2ee1d329a501ba4781db4145dc951c798
> > > change-id: 20230719-nfsd-acl-5ab61537e4e6
> > >
> > > Best regards,
> > > --
> > > Jeff Layton <jlayton@xxxxxxxxxx>
> > >
> >
>
> --
> Jeff Layton <jlayton@xxxxxxxxxx>

--
Chuck Lever

Next message: Muhammad Usama Anjum: "Re: [v2] fs/proc/task_mmu: Implement IOCTL for efficient page table scanning"
Previous message: Nicolas Dufresne: "Re: Stateless Encoding uAPI Discussion and Proposal"
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