c7c556f1e8
Refactor the logic for changing SELinux policy booleans in a similar manner to the refactoring of policy load, thereby reducing the size of the critical section when the policy write-lock is held and making it easier to convert the policy rwlock to RCU in the future. Instead of directly modifying the policydb in place, modify a copy and then swap it into place through a single pointer update. Only fully copy the portions of the policydb that are affected by boolean changes to avoid the full cost of a deep policydb copy. Introduce another level of indirection for the sidtab since changing booleans does not require updating the sidtab, unlike policy load. While we are here, create a common helper for notifying other kernel components and userspace of a policy change and call it from both security_set_bools() and selinux_policy_commit(). Based on an old (2004) patch by Kaigai Kohei [1] to convert the policy rwlock to RCU that was deferred at the time since it did not significantly improve performance and introduced complexity. Peter Enderborg later submitted a patch series to convert to RCU [2] that would have made changing booleans a much more expensive operation by requiring a full policydb_write();policydb_read(); sequence to deep copy the entire policydb and also had concerns regarding atomic allocations. This change is now simplified by the earlier work to encapsulate policy state in the selinux_policy struct and to refactor policy load. After this change, the last major obstacle to converting the policy rwlock to RCU is likely the sidtab live convert support. [1] https://lore.kernel.org/selinux/6e2f9128-e191-ebb3-0e87-74bfccb0767f@tycho.nsa.gov/ [2] https://lore.kernel.org/selinux/20180530141104.28569-1-peter.enderborg@sony.com/ Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
119 lines
3.7 KiB
C
119 lines
3.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* An access vector table (avtab) is a hash table
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* of access vectors and transition types indexed
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* by a type pair and a class. An access vector
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* table is used to represent the type enforcement
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* tables.
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*
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* Author : Stephen Smalley, <sds@tycho.nsa.gov>
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*/
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/* Updated: Frank Mayer <mayerf@tresys.com> and Karl MacMillan <kmacmillan@tresys.com>
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*
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* Added conditional policy language extensions
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*
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* Copyright (C) 2003 Tresys Technology, LLC
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*
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* Updated: Yuichi Nakamura <ynakam@hitachisoft.jp>
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* Tuned number of hash slots for avtab to reduce memory usage
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*/
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#ifndef _SS_AVTAB_H_
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#define _SS_AVTAB_H_
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#include "security.h"
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struct avtab_key {
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u16 source_type; /* source type */
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u16 target_type; /* target type */
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u16 target_class; /* target object class */
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#define AVTAB_ALLOWED 0x0001
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#define AVTAB_AUDITALLOW 0x0002
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#define AVTAB_AUDITDENY 0x0004
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#define AVTAB_AV (AVTAB_ALLOWED | AVTAB_AUDITALLOW | AVTAB_AUDITDENY)
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#define AVTAB_TRANSITION 0x0010
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#define AVTAB_MEMBER 0x0020
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#define AVTAB_CHANGE 0x0040
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#define AVTAB_TYPE (AVTAB_TRANSITION | AVTAB_MEMBER | AVTAB_CHANGE)
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/* extended permissions */
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#define AVTAB_XPERMS_ALLOWED 0x0100
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#define AVTAB_XPERMS_AUDITALLOW 0x0200
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#define AVTAB_XPERMS_DONTAUDIT 0x0400
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#define AVTAB_XPERMS (AVTAB_XPERMS_ALLOWED | \
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AVTAB_XPERMS_AUDITALLOW | \
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AVTAB_XPERMS_DONTAUDIT)
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#define AVTAB_ENABLED_OLD 0x80000000 /* reserved for used in cond_avtab */
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#define AVTAB_ENABLED 0x8000 /* reserved for used in cond_avtab */
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u16 specified; /* what field is specified */
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};
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/*
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* For operations that require more than the 32 permissions provided by the avc
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* extended permissions may be used to provide 256 bits of permissions.
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*/
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struct avtab_extended_perms {
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/* These are not flags. All 256 values may be used */
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#define AVTAB_XPERMS_IOCTLFUNCTION 0x01
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#define AVTAB_XPERMS_IOCTLDRIVER 0x02
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/* extension of the avtab_key specified */
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u8 specified; /* ioctl, netfilter, ... */
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/*
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* if 256 bits is not adequate as is often the case with ioctls, then
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* multiple extended perms may be used and the driver field
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* specifies which permissions are included.
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*/
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u8 driver;
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/* 256 bits of permissions */
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struct extended_perms_data perms;
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};
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struct avtab_datum {
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union {
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u32 data; /* access vector or type value */
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struct avtab_extended_perms *xperms;
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} u;
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};
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struct avtab_node {
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struct avtab_key key;
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struct avtab_datum datum;
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struct avtab_node *next;
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};
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struct avtab {
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struct avtab_node **htable;
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u32 nel; /* number of elements */
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u32 nslot; /* number of hash slots */
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u32 mask; /* mask to compute hash func */
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};
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void avtab_init(struct avtab *h);
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int avtab_alloc(struct avtab *, u32);
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int avtab_duplicate(struct avtab *new, struct avtab *orig);
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struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *k);
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void avtab_destroy(struct avtab *h);
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void avtab_hash_eval(struct avtab *h, char *tag);
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struct policydb;
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int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
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int (*insert)(struct avtab *a, struct avtab_key *k,
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struct avtab_datum *d, void *p),
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void *p);
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int avtab_read(struct avtab *a, void *fp, struct policydb *pol);
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int avtab_write_item(struct policydb *p, struct avtab_node *cur, void *fp);
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int avtab_write(struct policydb *p, struct avtab *a, void *fp);
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struct avtab_node *avtab_insert_nonunique(struct avtab *h, struct avtab_key *key,
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struct avtab_datum *datum);
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struct avtab_node *avtab_search_node(struct avtab *h, struct avtab_key *key);
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struct avtab_node *avtab_search_node_next(struct avtab_node *node, int specified);
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#define MAX_AVTAB_HASH_BITS 16
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#define MAX_AVTAB_HASH_BUCKETS (1 << MAX_AVTAB_HASH_BITS)
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#endif /* _SS_AVTAB_H_ */
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