From: Andreas Gruenbacher <agruenba@redhat.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
"Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
"J. Bruce Fields" <bfields@fieldses.org>,
Jeff Layton <jlayton@poochiereds.net>,
Trond Myklebust <trond.myklebust@primarydata.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Dave Chinner <david@fromorbit.com>,
linux-ext4@vger.kernel.org, xfs@oss.sgi.com,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
linux-api@vger.kernel.org
Subject: [PATCH v27 08/21] richacl: Compute maximum file masks from an acl
Date: Tue, 11 Oct 2016 14:50:43 +0200 [thread overview]
Message-ID: <1476190256-1677-9-git-send-email-agruenba@redhat.com> (raw)
In-Reply-To: <1476190256-1677-1-git-send-email-agruenba@redhat.com>
Compute upper bound owner, group, and other file masks with as few
permissions as possible without denying any permissions that the NFSv4
acl in a richacl grants.
This algorithm is used when a file inherits an acl at create time and
when an acl is set via a mechanism that does not provide file masks
(such as setting an acl via nfsd). When user-space sets an acl via
setxattr, the extended attribute already includes the file masks.
Setting an acl also sets the file mode permission bits: they are
determined by the file masks; see richacl_masks_to_mode().
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
---
fs/richacl.c | 157 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/richacl.h | 1 +
2 files changed, 158 insertions(+)
diff --git a/fs/richacl.c b/fs/richacl.c
index b7e96d0..0443090 100644
--- a/fs/richacl.c
+++ b/fs/richacl.c
@@ -303,3 +303,160 @@ richacl_permission(struct inode *inode, const struct richacl *acl,
return denied ? -EACCES : 0;
}
EXPORT_SYMBOL_GPL(richacl_permission);
+
+/*
+ * Note: functions like richacl_allowed_to_who(), richacl_group_class_allowed(),
+ * and richacl_compute_max_masks() iterate through the entire acl in reverse
+ * order as an optimization.
+ *
+ * In the standard algorithm, aces are considered in forward order. When a
+ * process matches an ace, the permissions in the ace are either allowed or
+ * denied depending on the ace type. Once a permission has been allowed or
+ * denied, it is no longer considered in further aces.
+ *
+ * By iterating through the acl in reverse order, we can compute the same
+ * result without having to keep track of which permissions have been allowed
+ * and denied already.
+ */
+
+/**
+ * richacl_allowed_to_who - permissions allowed to a specific who value
+ *
+ * Compute the maximum mask values allowed to a specific who value, taking
+ * everyone@ aces into account.
+ */
+static unsigned int richacl_allowed_to_who(struct richacl *acl,
+ struct richace *who)
+{
+ struct richace *ace;
+ unsigned int allowed = 0;
+
+ richacl_for_each_entry_reverse(ace, acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_same_identifier(ace, who) ||
+ richace_is_everyone(ace)) {
+ if (richace_is_allow(ace))
+ allowed |= ace->e_mask;
+ else if (richace_is_deny(ace))
+ allowed &= ~ace->e_mask;
+ }
+ }
+ return allowed;
+}
+
+/**
+ * richacl_group_class_allowed - maximum permissions of the group class
+ *
+ * Compute the maximum mask values allowed to a process in the group class
+ * (i.e., a process which is not the owner but is in the owning group or
+ * matches a user or group acl entry). This includes permissions granted or
+ * denied by everyone@ aces.
+ *
+ * See richacl_compute_max_masks().
+ */
+static unsigned int richacl_group_class_allowed(struct richacl *acl)
+{
+ struct richace *ace;
+ unsigned int everyone_allowed = 0, group_class_allowed = 0;
+ int had_group_ace = 0;
+
+ richacl_for_each_entry_reverse(ace, acl) {
+ if (richace_is_inherit_only(ace) ||
+ richace_is_owner(ace))
+ continue;
+
+ if (richace_is_everyone(ace)) {
+ if (richace_is_allow(ace))
+ everyone_allowed |= ace->e_mask;
+ else if (richace_is_deny(ace))
+ everyone_allowed &= ~ace->e_mask;
+ } else {
+ group_class_allowed |=
+ richacl_allowed_to_who(acl, ace);
+
+ if (richace_is_group(ace))
+ had_group_ace = 1;
+ }
+ }
+ /*
+ * If the acl doesn't contain any group@ aces, richacl_allowed_to_who()
+ * wasn't called for the owning group. We could make that call now, but
+ * we already know the result (everyone_allowed).
+ */
+ if (!had_group_ace)
+ group_class_allowed |= everyone_allowed;
+ return group_class_allowed;
+}
+
+/**
+ * richacl_compute_max_masks - compute upper bound masks
+ *
+ * Computes upper bound owner, group, and other masks so that none of the
+ * permissions allowed by the acl are disabled.
+ *
+ * We don't make assumptions about who the owner is so that the owner can
+ * change with no effect on the file masks or file mode permission bits; this
+ * means that we must assume that all entries can match the owner.
+ */
+void richacl_compute_max_masks(struct richacl *acl)
+{
+ unsigned int gmask = ~0;
+ struct richace *ace;
+
+ /*
+ * @gmask contains all permissions which the group class is ever
+ * allowed. We use it to avoid adding permissions to the group mask
+ * from everyone@ allow aces which the group class is always denied
+ * through other aces. For example, the following acl would otherwise
+ * result in a group mask of rw:
+ *
+ * group@:w::deny
+ * everyone@:rw::allow
+ *
+ * Avoid computing @gmask for acls which do not include any group class
+ * deny aces: in such acls, the group class is never denied any
+ * permissions from everyone@ allow aces, and the group class cannot
+ * have fewer permissions than the other class.
+ */
+
+restart:
+ acl->a_owner_mask = 0;
+ acl->a_group_mask = 0;
+ acl->a_other_mask = 0;
+
+ richacl_for_each_entry_reverse(ace, acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+
+ if (richace_is_owner(ace)) {
+ if (richace_is_allow(ace))
+ acl->a_owner_mask |= ace->e_mask;
+ else if (richace_is_deny(ace))
+ acl->a_owner_mask &= ~ace->e_mask;
+ } else if (richace_is_everyone(ace)) {
+ if (richace_is_allow(ace)) {
+ acl->a_owner_mask |= ace->e_mask;
+ acl->a_group_mask |= ace->e_mask & gmask;
+ acl->a_other_mask |= ace->e_mask;
+ } else if (richace_is_deny(ace)) {
+ acl->a_owner_mask &= ~ace->e_mask;
+ acl->a_group_mask &= ~ace->e_mask;
+ acl->a_other_mask &= ~ace->e_mask;
+ }
+ } else {
+ if (richace_is_allow(ace)) {
+ acl->a_owner_mask |= ace->e_mask & gmask;
+ acl->a_group_mask |= ace->e_mask & gmask;
+ } else if (richace_is_deny(ace) && gmask == ~0) {
+ gmask = richacl_group_class_allowed(acl);
+ if (likely(gmask != ~0))
+ /* should always be true */
+ goto restart;
+ }
+ }
+ }
+
+ acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED);
+}
+EXPORT_SYMBOL_GPL(richacl_compute_max_masks);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index beeec35..700888b 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -178,5 +178,6 @@ extern void richace_copy(struct richace *, const struct richace *);
extern int richacl_masks_to_mode(const struct richacl *);
extern unsigned int richacl_mode_to_mask(umode_t);
extern int richacl_permission(struct inode *, const struct richacl *, int);
+extern void richacl_compute_max_masks(struct richacl *);
#endif /* __RICHACL_H */
--
2.7.4
next prev parent reply other threads:[~2016-10-11 12:51 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-11 12:50 [PATCH v27 00/21] Richacls (Core and Ext4) Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 01/21] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 02/21] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher
2016-12-02 9:22 ` Miklos Szeredi
2017-02-13 15:34 ` Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 03/21] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD " Andreas Gruenbacher
2016-12-02 9:57 ` Miklos Szeredi
2016-12-06 20:15 ` J. Bruce Fields
2016-12-06 21:13 ` Jeremy Allison
2016-12-06 21:25 ` Miklos Szeredi
2016-12-06 21:36 ` Jeremy Allison
2017-02-13 15:40 ` Andreas Gruenbacher
2017-02-13 15:42 ` Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 04/21] vfs: Add permission flags for setting file attributes Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 05/21] richacl: In-memory representation and helper functions Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 06/21] richacl: Permission mapping functions Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 07/21] richacl: Permission check algorithm Andreas Gruenbacher
2016-10-11 12:50 ` Andreas Gruenbacher [this message]
2016-10-11 12:50 ` [PATCH v27 09/21] vfs: Cache base_acl objects in inodes Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 10/21] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 11/21] vfs: Cache richacl in struct inode Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 12/21] richacl: Update the file masks in chmod() Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 13/21] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 14/21] richacl: Create-time inheritance Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 15/21] richacl: Automatic Inheritance Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 16/21] richacl: xattr mapping functions Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 17/21] richacl: Add richacl xattr handler Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 18/21] vfs: Add richacl permission checking Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 19/21] vfs: Move check_posix_acl and check_richacl out of fs/namei.c Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 20/21] ext4: Add richacl support Andreas Gruenbacher
2016-10-11 12:50 ` [PATCH v27 21/21] ext4: Add richacl feature flag Andreas Gruenbacher
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1476190256-1677-9-git-send-email-agruenba@redhat.com \
--to=agruenba@redhat.com \
--cc=adilger.kernel@dilger.ca \
--cc=anna.schumaker@netapp.com \
--cc=bfields@fieldses.org \
--cc=david@fromorbit.com \
--cc=hch@infradead.org \
--cc=jlayton@poochiereds.net \
--cc=linux-api@vger.kernel.org \
--cc=linux-cifs@vger.kernel.org \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=trond.myklebust@primarydata.com \
--cc=tytso@mit.edu \
--cc=viro@zeniv.linux.org.uk \
--cc=xfs@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).