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Message-ID: <CAHpGcMLshi34rjcb4ygu3CTz8Vmf_Cb7pJym25qK8vz8+gLDvw@mail.gmail.com>
Date: Thu, 20 Jul 2023 10:43:44 +0200
From: Andreas Grünbacher <andreas.gruenbacher@...il.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: Chuck Lever <chuck.lever@...cle.com>, Neil Brown <neilb@...e.de>,
Olga Kornievskaia <kolga@...app.com>,
Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
linux-nfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
Ondrej Valousek <ondrej.valousek@...semi.com>,
Andreas Gruenbacher <agruen@...hat.com>
Subject: Re: [PATCH] nfsd: inherit required unset default acls from effective set
Am Mi., 19. Juli 2023 um 23:22 Uhr schrieb Andreas Grünbacher
<andreas.gruenbacher@...il.com>:
>
> Hi Jeff,
>
> this patch seems useful, thanks.
>
> Am Mi., 19. Juli 2023 um 19:56 Uhr schrieb Jeff Layton <jlayton@...nel.org>:
> > A well-formed NFSv4 ACL will always contain OWNER@...OUP@...ERYONE@
> > 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.
>
> NFSv4 ACLs actually don't *need* to have OWNER@...OUP@...ERYONE@
> entries; that's merely a result of translating POSIX ACLs (or file
> modes) to NFSv4 ACLs.
>
> > 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
>
> This resulting NFSv4 ACL is still rather dull; we end up with an
> inherit-only entry for each effective entry. Those could all be
> combined, resulting in:
>
> A:fd:OWNER@:rwaDxtTcCy
> A:fd:1000:rwaDxtcy
> A:fd:GROUP@:rxtcy
> A:fd:EVERYONE@:rxtcy
>
> This will be the common case, so maybe matching entry pairs can either
> be recombined or not generated in the first place as a further
> improvement.
>
> > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2136452
> > Reported-by: Ondrej Valousek <ondrej.valousek@...semi.com>
> > Suggested-by: Andreas Gruenbacher <agruen@...hat.com>
> > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > ---
> > fs/nfsd/nfs4acl.c | 32 +++++++++++++++++++++++++++++---
> > 1 file changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
> > index 518203821790..64e45551d1b6 100644
> > --- a/fs/nfsd/nfs4acl.c
> > +++ b/fs/nfsd/nfs4acl.c
> > @@ -441,7 +441,8 @@ struct posix_ace_state_array {
> > * calculated so far: */
> >
> > struct posix_acl_state {
> > - int empty;
> > + bool empty;
> > + unsigned char valid;
>
> Hmm, "valid" is a bitmask here but it only matters whether it is zero.
> Shouldn't a bool be good enough? Also, this variable indicates whether
> special "who" values are present (and which), so the name "valid"
> probably isn't the best choice.
>
> > struct posix_ace_state owner;
> > struct posix_ace_state group;
> > struct posix_ace_state other;
> > @@ -457,7 +458,7 @@ init_state(struct posix_acl_state *state, int cnt)
> > int alloc;
> >
> > memset(state, 0, sizeof(struct posix_acl_state));
> > - state->empty = 1;
> > + state->empty = true;
> > /*
> > * 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
> > @@ -624,7 +625,7 @@ static void process_one_v4_ace(struct posix_acl_state *state,
> > u32 mask = ace->access_mask;
> > int i;
> >
> > - state->empty = 0;
> > + state->empty = false;
> >
> > switch (ace2type(ace)) {
> > case ACL_USER_OBJ:
> > @@ -633,6 +634,7 @@ static void process_one_v4_ace(struct posix_acl_state *state,
> > } else {
> > deny_bits(&state->owner, mask);
> > }
> > + state->valid |= ACL_USER_OBJ;
> > break;
> > case ACL_USER:
> > i = find_uid(state, ace->who_uid);
> > @@ -655,6 +657,7 @@ static void process_one_v4_ace(struct posix_acl_state *state,
> > deny_bits_array(state->users, mask);
> > deny_bits_array(state->groups, mask);
> > }
> > + state->valid |= ACL_GROUP_OBJ;
> > break;
> > case ACL_GROUP:
> > i = find_gid(state, ace->who_gid);
> > @@ -686,6 +689,7 @@ static void process_one_v4_ace(struct posix_acl_state *state,
> > deny_bits_array(state->users, mask);
> > deny_bits_array(state->groups, mask);
> > }
> > + state->valid |= ACL_OTHER;
> > }
> > }
> >
> > @@ -726,6 +730,28 @@ 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."
> > + *
> > + * If none of the requisite ACEs were set, and some explicit user or group
> > + * ACEs were, copy the requisite entries from the effective set.
> > + */
> > + if (!default_acl_state.valid &&
> > + (default_acl_state.users->n || default_acl_state.groups->n)) {
> > + default_acl_state.owner = effective_acl_state.owner;
> > + default_acl_state.group = effective_acl_state.group;
> > + default_acl_state.other = effective_acl_state.other;
> > + }
> > +
The other thing I'm wondering about is whether it would make more
sense to fake up for missing entries individually as setfacl does:
http://git.savannah.nongnu.org/cgit/acl.git/tree/tools/do_set.c#n368
> > *pacl = posix_state_to_acl(&effective_acl_state, flags);
> > if (IS_ERR(*pacl)) {
> > ret = PTR_ERR(*pacl);
> >
> > ---
> > base-commit: 9d985ab8ed33176c3c0380b7de589ea2ae51a48d
> > change-id: 20230719-nfsd-acl-5ab61537e4e6
> >
> > Best regards,
> > --
> > Jeff Layton <jlayton@...nel.org>
Thanks,
Andreas
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