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116f21bb96
As noted in Documentation/atomic_t.txt, if we don't need the RMW atomic operations, we should only use READ_ONCE()/WRITE_ONCE() + smp_rmb()/smp_wmb() where necessary (or the combined variants smp_load_acquire()/smp_store_release()). This patch converts the sidtab code to use regular u32 for the counter and reverse lookup cache and use the appropriate operations instead of atomic_get()/atomic_set(). Note that when reading/updating the reverse lookup cache we don't need memory barriers as it doesn't need to be consistent or accurate. We can now also replace some atomic ops with regular loads (when under spinlock) and stores (for conversion target fields that are always accessed under the master table's spinlock). We can now also bump SIDTAB_MAX to U32_MAX as we can use the full u32 range again. Suggested-by: Jann Horn <jannh@google.com> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com> Reviewed-by: Jann Horn <jannh@google.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
106 lines
2.7 KiB
C
106 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* A security identifier table (sidtab) is a lookup table
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* of security context structures indexed by SID value.
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*
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* Original author: Stephen Smalley, <sds@tycho.nsa.gov>
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* Author: Ondrej Mosnacek, <omosnacek@gmail.com>
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*
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* Copyright (C) 2018 Red Hat, Inc.
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*/
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#ifndef _SS_SIDTAB_H_
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#define _SS_SIDTAB_H_
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#include <linux/spinlock_types.h>
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#include <linux/log2.h>
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#include "context.h"
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struct sidtab_entry_leaf {
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struct context context;
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};
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struct sidtab_node_inner;
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struct sidtab_node_leaf;
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union sidtab_entry_inner {
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struct sidtab_node_inner *ptr_inner;
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struct sidtab_node_leaf *ptr_leaf;
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};
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/* align node size to page boundary */
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#define SIDTAB_NODE_ALLOC_SHIFT PAGE_SHIFT
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#define SIDTAB_NODE_ALLOC_SIZE PAGE_SIZE
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#define size_to_shift(size) ((size) == 1 ? 1 : (const_ilog2((size) - 1) + 1))
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#define SIDTAB_INNER_SHIFT \
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(SIDTAB_NODE_ALLOC_SHIFT - size_to_shift(sizeof(union sidtab_entry_inner)))
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#define SIDTAB_INNER_ENTRIES ((size_t)1 << SIDTAB_INNER_SHIFT)
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#define SIDTAB_LEAF_ENTRIES \
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(SIDTAB_NODE_ALLOC_SIZE / sizeof(struct sidtab_entry_leaf))
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#define SIDTAB_MAX_BITS 32
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#define SIDTAB_MAX U32_MAX
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/* ensure enough tree levels for SIDTAB_MAX entries */
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#define SIDTAB_MAX_LEVEL \
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DIV_ROUND_UP(SIDTAB_MAX_BITS - size_to_shift(SIDTAB_LEAF_ENTRIES), \
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SIDTAB_INNER_SHIFT)
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struct sidtab_node_leaf {
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struct sidtab_entry_leaf entries[SIDTAB_LEAF_ENTRIES];
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};
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struct sidtab_node_inner {
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union sidtab_entry_inner entries[SIDTAB_INNER_ENTRIES];
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};
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struct sidtab_isid_entry {
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int set;
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struct context context;
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};
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struct sidtab_convert_params {
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int (*func)(struct context *oldc, struct context *newc, void *args);
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void *args;
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struct sidtab *target;
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};
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#define SIDTAB_RCACHE_SIZE 3
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struct sidtab {
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/*
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* lock-free read access only for as many items as a prior read of
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* 'count'
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*/
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union sidtab_entry_inner roots[SIDTAB_MAX_LEVEL + 1];
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/*
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* access atomically via {READ|WRITE}_ONCE(); only increment under
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* spinlock
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*/
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u32 count;
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/* access only under spinlock */
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struct sidtab_convert_params *convert;
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spinlock_t lock;
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/* reverse lookup cache - access atomically via {READ|WRITE}_ONCE() */
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u32 rcache[SIDTAB_RCACHE_SIZE];
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/* index == SID - 1 (no entry for SECSID_NULL) */
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struct sidtab_isid_entry isids[SECINITSID_NUM];
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};
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int sidtab_init(struct sidtab *s);
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int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context);
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struct context *sidtab_search(struct sidtab *s, u32 sid);
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struct context *sidtab_search_force(struct sidtab *s, u32 sid);
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int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params);
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int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid);
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void sidtab_destroy(struct sidtab *s);
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#endif /* _SS_SIDTAB_H_ */
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