165 lines
5.0 KiB
Diff
165 lines
5.0 KiB
Diff
From: Andreas Gruenbacher <agruen@suse.de>
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Date: Fri, 11 Jun 2010 16:12:47 +0530
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Subject: [PATCH 06/16] richacl: Compute maximum file masks from an acl
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Patch-mainline: not yet
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Compute upper bound owner, group, and other file masks with as few
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permissions as possible without denying any permissions that the NFSv4
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acl in a richacl grants.
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This algorithm is used when a file inherits an acl at create time and
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when an acl is set via a mechanism that does not specify file modes
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(such as via nfsd). When user-space sets an acl, the file masks are
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passed in as part of the xattr.
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When setting a richacl, the file masks determine what the file
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permission bits will be set to; see richacl_masks_to_mode().
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Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
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Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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---
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fs/richacl_base.c | 125 ++++++++++++++++++++++++++++++++++++++++++++++++
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include/linux/richacl.h | 1
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2 files changed, 126 insertions(+)
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--- a/fs/richacl_base.c
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+++ b/fs/richacl_base.c
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@@ -205,3 +205,128 @@ richace_set_who(struct richace *ace, con
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return 0;
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}
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EXPORT_SYMBOL_GPL(richace_set_who);
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+
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+/**
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+ * richacl_allowed_to_who - mask flags allowed to a specific who value
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+ *
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+ * Computes the mask values allowed to a specific who value, taking
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+ * EVERYONE@ entries into account.
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+ */
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+static unsigned int richacl_allowed_to_who(struct richacl *acl,
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+ struct richace *who)
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+{
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+ struct richace *ace;
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+ unsigned int allowed = 0;
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+
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+ richacl_for_each_entry_reverse(ace, acl) {
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+ if (richace_is_inherit_only(ace))
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+ continue;
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+ if (richace_is_same_identifier(ace, who) ||
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+ richace_is_everyone(ace)) {
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+ if (richace_is_allow(ace))
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+ allowed |= ace->e_mask;
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+ else if (richace_is_deny(ace))
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+ allowed &= ~ace->e_mask;
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+ }
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+ }
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+ return allowed;
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+}
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+
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+/**
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+ * richacl_group_class_allowed - maximum permissions the group class is allowed
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+ *
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+ * See richacl_compute_max_masks().
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+ */
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+static unsigned int richacl_group_class_allowed(struct richacl *acl)
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+{
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+ struct richace *ace;
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+ unsigned int everyone_allowed = 0, group_class_allowed = 0;
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+ int had_group_ace = 0;
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+
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+ richacl_for_each_entry_reverse(ace, acl) {
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+ if (richace_is_inherit_only(ace) ||
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+ richace_is_owner(ace))
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+ continue;
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+
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+ if (richace_is_everyone(ace)) {
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+ if (richace_is_allow(ace))
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+ everyone_allowed |= ace->e_mask;
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+ else if (richace_is_deny(ace))
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+ everyone_allowed &= ~ace->e_mask;
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+ } else {
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+ group_class_allowed |=
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+ richacl_allowed_to_who(acl, ace);
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+
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+ if (richace_is_group(ace))
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+ had_group_ace = 1;
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+ }
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+ }
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+ if (!had_group_ace)
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+ group_class_allowed |= everyone_allowed;
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+ return group_class_allowed;
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+}
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+
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+/**
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+ * richacl_compute_max_masks - compute upper bound masks
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+ *
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+ * Computes upper bound owner, group, and other masks so that none of
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+ * the mask flags allowed by the acl are disabled (for any choice of the
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+ * file owner or group membership).
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+ */
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+void richacl_compute_max_masks(struct richacl *acl)
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+{
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+ unsigned int gmask = ~0;
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+ struct richace *ace;
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+
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+ /*
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+ * @gmask contains all permissions which the group class is ever
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+ * allowed. We use it to avoid adding permissions to the group mask
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+ * from everyone@ allow aces which the group class is always denied
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+ * through other aces. For example, the following acl would otherwise
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+ * result in a group mask or rw:
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+ *
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+ * group@:w::deny
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+ * everyone@:rw::allow
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+ *
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+ * Avoid computing @gmask for acls which do not include any group class
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+ * deny aces: in such acls, the group class is never denied any
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+ * permissions from everyone@ allow aces.
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+ */
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+
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+restart:
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+ acl->a_owner_mask = 0;
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+ acl->a_group_mask = 0;
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+ acl->a_other_mask = 0;
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+
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+ richacl_for_each_entry_reverse(ace, acl) {
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+ if (richace_is_inherit_only(ace))
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+ continue;
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+
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+ if (richace_is_owner(ace)) {
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+ if (richace_is_allow(ace))
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+ acl->a_owner_mask |= ace->e_mask;
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+ else if (richace_is_deny(ace))
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+ acl->a_owner_mask &= ~ace->e_mask;
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+ } else if (richace_is_everyone(ace)) {
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+ if (richace_is_allow(ace)) {
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+ acl->a_owner_mask |= ace->e_mask;
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+ acl->a_group_mask |= ace->e_mask & gmask;
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+ acl->a_other_mask |= ace->e_mask;
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+ } else if (richace_is_deny(ace)) {
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+ acl->a_owner_mask &= ~ace->e_mask;
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+ acl->a_group_mask &= ~ace->e_mask;
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+ acl->a_other_mask &= ~ace->e_mask;
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+ }
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+ } else {
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+ if (richace_is_allow(ace)) {
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+ acl->a_owner_mask |= ace->e_mask & gmask;
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+ acl->a_group_mask |= ace->e_mask & gmask;
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+ } else if (richace_is_deny(ace) && gmask == ~0) {
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+ gmask = richacl_group_class_allowed(acl);
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+ if (likely(gmask != ~0)) /* should always be true */
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+ goto restart;
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+ }
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+ }
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+ }
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+}
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+EXPORT_SYMBOL_GPL(richacl_compute_max_masks);
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--- a/include/linux/richacl.h
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+++ b/include/linux/richacl.h
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@@ -268,5 +268,6 @@ extern int richace_set_who(struct richac
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extern int richacl_masks_to_mode(const struct richacl *);
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extern unsigned int richacl_mode_to_mask(mode_t);
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extern unsigned int richacl_want_to_mask(int);
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+extern void richacl_compute_max_masks(struct richacl *);
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#endif /* __RICHACL_H */
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