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Message-ID: <ZL6AKlkloZQwlmPG@tissot.1015granger.net>
Date: Mon, 24 Jul 2023 09:44:10 -0400
From: Chuck Lever <chuck.lever@...cle.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: Neil Brown <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>,
Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
Andreas Gruenbacher <agruenba@...hat.com>,
linux-nfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
Ondrej Valousek <ondrej.valousek@...semi.com>
Subject: Re: [PATCH v2] nfsd: inherit required unset default acls from
effective set
On Mon, Jul 24, 2023 at 08:13:05AM -0400, Jeff Layton wrote:
> 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.
>
> 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@...semi.com>
> Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2136452
> Suggested-by: Andreas Gruenbacher <agruenba@...hat.com>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
> 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@kernel.org
> ---
> 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).
> 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@...nel.org>
>
--
Chuck Lever
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