linux/security/selinux/ss/sidtab.c

501 lines
11 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Implementation of the SID table type.
*
* Original author: Stephen Smalley, <sds@tycho.nsa.gov>
* Author: Ondrej Mosnacek, <omosnacek@gmail.com>
*
* Copyright (C) 2018 Red Hat, Inc.
*/
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include "flask.h"
#include "security.h"
#include "sidtab.h"
int sidtab_init(struct sidtab *s)
{
u32 i;
memset(s->roots, 0, sizeof(s->roots));
for (i = 0; i < SIDTAB_RCACHE_SIZE; i++)
atomic_set(&s->rcache[i], -1);
for (i = 0; i < SECINITSID_NUM; i++)
s->isids[i].set = 0;
atomic_set(&s->count, 0);
s->convert = NULL;
spin_lock_init(&s->lock);
return 0;
}
int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
{
struct sidtab_isid_entry *entry;
int rc;
if (sid == 0 || sid > SECINITSID_NUM)
return -EINVAL;
entry = &s->isids[sid - 1];
rc = context_cpy(&entry->context, context);
if (rc)
return rc;
entry->set = 1;
return 0;
}
static u32 sidtab_level_from_count(u32 count)
{
u32 capacity = SIDTAB_LEAF_ENTRIES;
u32 level = 0;
while (count > capacity) {
capacity <<= SIDTAB_INNER_SHIFT;
++level;
}
return level;
}
static int sidtab_alloc_roots(struct sidtab *s, u32 level)
{
u32 l;
if (!s->roots[0].ptr_leaf) {
s->roots[0].ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
GFP_ATOMIC);
if (!s->roots[0].ptr_leaf)
return -ENOMEM;
}
for (l = 1; l <= level; ++l)
if (!s->roots[l].ptr_inner) {
s->roots[l].ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
GFP_ATOMIC);
if (!s->roots[l].ptr_inner)
return -ENOMEM;
s->roots[l].ptr_inner->entries[0] = s->roots[l - 1];
}
return 0;
}
static struct context *sidtab_do_lookup(struct sidtab *s, u32 index, int alloc)
{
union sidtab_entry_inner *entry;
u32 level, capacity_shift, leaf_index = index / SIDTAB_LEAF_ENTRIES;
/* find the level of the subtree we need */
level = sidtab_level_from_count(index + 1);
capacity_shift = level * SIDTAB_INNER_SHIFT;
/* allocate roots if needed */
if (alloc && sidtab_alloc_roots(s, level) != 0)
return NULL;
/* lookup inside the subtree */
entry = &s->roots[level];
while (level != 0) {
capacity_shift -= SIDTAB_INNER_SHIFT;
--level;
entry = &entry->ptr_inner->entries[leaf_index >> capacity_shift];
leaf_index &= ((u32)1 << capacity_shift) - 1;
if (!entry->ptr_inner) {
if (alloc)
entry->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
GFP_ATOMIC);
if (!entry->ptr_inner)
return NULL;
}
}
if (!entry->ptr_leaf) {
if (alloc)
entry->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
GFP_ATOMIC);
if (!entry->ptr_leaf)
return NULL;
}
return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES].context;
}
static struct context *sidtab_lookup(struct sidtab *s, u32 index)
{
u32 count = (u32)atomic_read(&s->count);
if (index >= count)
return NULL;
/* read entries after reading count */
smp_rmb();
return sidtab_do_lookup(s, index, 0);
}
static struct context *sidtab_lookup_initial(struct sidtab *s, u32 sid)
{
return s->isids[sid - 1].set ? &s->isids[sid - 1].context : NULL;
}
static struct context *sidtab_search_core(struct sidtab *s, u32 sid, int force)
{
struct context *context;
if (sid != 0) {
if (sid > SECINITSID_NUM)
context = sidtab_lookup(s, sid - (SECINITSID_NUM + 1));
else
context = sidtab_lookup_initial(s, sid);
if (context && (!context->len || force))
return context;
}
return sidtab_lookup_initial(s, SECINITSID_UNLABELED);
}
struct context *sidtab_search(struct sidtab *s, u32 sid)
{
return sidtab_search_core(s, sid, 0);
}
struct context *sidtab_search_force(struct sidtab *s, u32 sid)
{
return sidtab_search_core(s, sid, 1);
}
static int sidtab_find_context(union sidtab_entry_inner entry,
u32 *pos, u32 count, u32 level,
struct context *context, u32 *index)
{
int rc;
u32 i;
if (level != 0) {
struct sidtab_node_inner *node = entry.ptr_inner;
i = 0;
while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
rc = sidtab_find_context(node->entries[i],
pos, count, level - 1,
context, index);
if (rc == 0)
return 0;
i++;
}
} else {
struct sidtab_node_leaf *node = entry.ptr_leaf;
i = 0;
while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
if (context_cmp(&node->entries[i].context, context)) {
*index = *pos;
return 0;
}
(*pos)++;
i++;
}
}
return -ENOENT;
}
static void sidtab_rcache_update(struct sidtab *s, u32 index, u32 pos)
{
while (pos > 0) {
atomic_set(&s->rcache[pos], atomic_read(&s->rcache[pos - 1]));
--pos;
}
atomic_set(&s->rcache[0], (int)index);
}
static void sidtab_rcache_push(struct sidtab *s, u32 index)
{
sidtab_rcache_update(s, index, SIDTAB_RCACHE_SIZE - 1);
}
static int sidtab_rcache_search(struct sidtab *s, struct context *context,
u32 *index)
{
u32 i;
for (i = 0; i < SIDTAB_RCACHE_SIZE; i++) {
int v = atomic_read(&s->rcache[i]);
if (v < 0)
continue;
if (context_cmp(sidtab_do_lookup(s, (u32)v, 0), context)) {
sidtab_rcache_update(s, (u32)v, i);
*index = (u32)v;
return 0;
}
}
return -ENOENT;
}
static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
u32 *index)
{
unsigned long flags;
u32 count = (u32)atomic_read(&s->count);
u32 count_locked, level, pos;
struct sidtab_convert_params *convert;
struct context *dst, *dst_convert;
int rc;
rc = sidtab_rcache_search(s, context, index);
if (rc == 0)
return 0;
level = sidtab_level_from_count(count);
/* read entries after reading count */
smp_rmb();
pos = 0;
rc = sidtab_find_context(s->roots[level], &pos, count, level,
context, index);
if (rc == 0) {
sidtab_rcache_push(s, *index);
return 0;
}
/* lock-free search failed: lock, re-search, and insert if not found */
spin_lock_irqsave(&s->lock, flags);
convert = s->convert;
count_locked = (u32)atomic_read(&s->count);
level = sidtab_level_from_count(count_locked);
/* if count has changed before we acquired the lock, then catch up */
while (count < count_locked) {
if (context_cmp(sidtab_do_lookup(s, count, 0), context)) {
sidtab_rcache_push(s, count);
*index = count;
rc = 0;
goto out_unlock;
}
++count;
}
/* bail out if we already reached max entries */
rc = -EOVERFLOW;
if (count >= SIDTAB_MAX)
goto out_unlock;
/* insert context into new entry */
rc = -ENOMEM;
dst = sidtab_do_lookup(s, count, 1);
if (!dst)
goto out_unlock;
rc = context_cpy(dst, context);
if (rc)
goto out_unlock;
/*
* if we are building a new sidtab, we need to convert the context
* and insert it there as well
*/
if (convert) {
rc = -ENOMEM;
dst_convert = sidtab_do_lookup(convert->target, count, 1);
if (!dst_convert) {
context_destroy(dst);
goto out_unlock;
}
rc = convert->func(context, dst_convert, convert->args);
if (rc) {
context_destroy(dst);
goto out_unlock;
}
/* at this point we know the insert won't fail */
atomic_set(&convert->target->count, count + 1);
}
if (context->len)
pr_info("SELinux: Context %s is not valid (left unmapped).\n",
context->str);
sidtab_rcache_push(s, count);
*index = count;
/* write entries before writing new count */
smp_wmb();
atomic_set(&s->count, count + 1);
rc = 0;
out_unlock:
spin_unlock_irqrestore(&s->lock, flags);
return rc;
}
int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid)
{
int rc;
u32 i;
for (i = 0; i < SECINITSID_NUM; i++) {
struct sidtab_isid_entry *entry = &s->isids[i];
if (entry->set && context_cmp(context, &entry->context)) {
*sid = i + 1;
return 0;
}
}
rc = sidtab_reverse_lookup(s, context, sid);
if (rc)
return rc;
*sid += SECINITSID_NUM + 1;
return 0;
}
static int sidtab_convert_tree(union sidtab_entry_inner *edst,
union sidtab_entry_inner *esrc,
u32 *pos, u32 count, u32 level,
struct sidtab_convert_params *convert)
{
int rc;
u32 i;
if (level != 0) {
if (!edst->ptr_inner) {
edst->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
GFP_KERNEL);
if (!edst->ptr_inner)
return -ENOMEM;
}
i = 0;
while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
rc = sidtab_convert_tree(&edst->ptr_inner->entries[i],
&esrc->ptr_inner->entries[i],
pos, count, level - 1,
convert);
if (rc)
return rc;
i++;
}
} else {
if (!edst->ptr_leaf) {
edst->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
GFP_KERNEL);
if (!edst->ptr_leaf)
return -ENOMEM;
}
i = 0;
while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
rc = convert->func(&esrc->ptr_leaf->entries[i].context,
&edst->ptr_leaf->entries[i].context,
convert->args);
if (rc)
return rc;
(*pos)++;
i++;
}
cond_resched();
}
return 0;
}
int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
{
unsigned long flags;
u32 count, level, pos;
int rc;
spin_lock_irqsave(&s->lock, flags);
/* concurrent policy loads are not allowed */
if (s->convert) {
spin_unlock_irqrestore(&s->lock, flags);
return -EBUSY;
}
count = (u32)atomic_read(&s->count);
level = sidtab_level_from_count(count);
/* allocate last leaf in the new sidtab (to avoid race with
* live convert)
*/
rc = sidtab_do_lookup(params->target, count - 1, 1) ? 0 : -ENOMEM;
if (rc) {
spin_unlock_irqrestore(&s->lock, flags);
return rc;
}
/* set count in case no new entries are added during conversion */
atomic_set(&params->target->count, count);
/* enable live convert of new entries */
s->convert = params;
/* we can safely do the rest of the conversion outside the lock */
spin_unlock_irqrestore(&s->lock, flags);
pr_info("SELinux: Converting %u SID table entries...\n", count);
/* convert all entries not covered by live convert */
pos = 0;
rc = sidtab_convert_tree(&params->target->roots[level],
&s->roots[level], &pos, count, level, params);
if (rc) {
/* we need to keep the old table - disable live convert */
spin_lock_irqsave(&s->lock, flags);
s->convert = NULL;
spin_unlock_irqrestore(&s->lock, flags);
}
return rc;
}
static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level)
{
u32 i;
if (level != 0) {
struct sidtab_node_inner *node = entry.ptr_inner;
if (!node)
return;
for (i = 0; i < SIDTAB_INNER_ENTRIES; i++)
sidtab_destroy_tree(node->entries[i], level - 1);
kfree(node);
} else {
struct sidtab_node_leaf *node = entry.ptr_leaf;
if (!node)
return;
for (i = 0; i < SIDTAB_LEAF_ENTRIES; i++)
context_destroy(&node->entries[i].context);
kfree(node);
}
}
void sidtab_destroy(struct sidtab *s)
{
u32 i, level;
for (i = 0; i < SECINITSID_NUM; i++)
if (s->isids[i].set)
context_destroy(&s->isids[i].context);
level = SIDTAB_MAX_LEVEL;
while (level && !s->roots[level].ptr_inner)
--level;
sidtab_destroy_tree(s->roots[level], level);
}