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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>
85 lines
2.4 KiB
C
85 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/* Authors: Karl MacMillan <kmacmillan@tresys.com>
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* Frank Mayer <mayerf@tresys.com>
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*
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* Copyright (C) 2003 - 2004 Tresys Technology, LLC
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*/
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#ifndef _CONDITIONAL_H_
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#define _CONDITIONAL_H_
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#include "avtab.h"
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#include "symtab.h"
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#include "policydb.h"
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#include "../include/conditional.h"
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#define COND_EXPR_MAXDEPTH 10
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/*
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* A conditional expression is a list of operators and operands
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* in reverse polish notation.
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*/
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struct cond_expr_node {
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#define COND_BOOL 1 /* plain bool */
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#define COND_NOT 2 /* !bool */
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#define COND_OR 3 /* bool || bool */
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#define COND_AND 4 /* bool && bool */
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#define COND_XOR 5 /* bool ^ bool */
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#define COND_EQ 6 /* bool == bool */
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#define COND_NEQ 7 /* bool != bool */
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#define COND_LAST COND_NEQ
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u32 expr_type;
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u32 bool;
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};
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struct cond_expr {
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struct cond_expr_node *nodes;
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u32 len;
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};
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/*
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* Each cond_node contains a list of rules to be enabled/disabled
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* depending on the current value of the conditional expression. This
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* struct is for that list.
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*/
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struct cond_av_list {
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struct avtab_node **nodes;
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u32 len;
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};
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/*
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* A cond node represents a conditional block in a policy. It
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* contains a conditional expression, the current state of the expression,
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* two lists of rules to enable/disable depending on the value of the
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* expression (the true list corresponds to if and the false list corresponds
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* to else)..
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*/
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struct cond_node {
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int cur_state;
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struct cond_expr expr;
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struct cond_av_list true_list;
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struct cond_av_list false_list;
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};
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void cond_policydb_init(struct policydb *p);
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void cond_policydb_destroy(struct policydb *p);
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int cond_init_bool_indexes(struct policydb *p);
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int cond_destroy_bool(void *key, void *datum, void *p);
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int cond_index_bool(void *key, void *datum, void *datap);
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int cond_read_bool(struct policydb *p, struct symtab *s, void *fp);
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int cond_read_list(struct policydb *p, void *fp);
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int cond_write_bool(void *key, void *datum, void *ptr);
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int cond_write_list(struct policydb *p, void *fp);
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void cond_compute_av(struct avtab *ctab, struct avtab_key *key,
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struct av_decision *avd, struct extended_perms *xperms);
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void cond_compute_xperms(struct avtab *ctab, struct avtab_key *key,
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struct extended_perms_decision *xpermd);
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void evaluate_cond_nodes(struct policydb *p);
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void cond_policydb_destroy_dup(struct policydb *p);
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int cond_policydb_dup(struct policydb *new, struct policydb *orig);
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#endif /* _CONDITIONAL_H_ */
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