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db.c
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db.c
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/**
* Enhanced Seccomp Filter DB
*
* Copyright (c) 2012,2016,2018 Red Hat <[email protected]>
* Copyright (c) 2019 Cisco Systems, Inc. <[email protected]>
* Copyright (c) 2022 Microsoft Corporation <[email protected]>
* Author: Paul Moore <[email protected]>
*/
/*
* This library is free software; you can redistribute it and/or modify it
* under the terms of version 2.1 of the GNU Lesser General Public License as
* published by the Free Software Foundation.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, see <https://www.gnu.org/licenses>.
*/
#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <seccomp.h>
#include "arch.h"
#include "db.h"
#include "system.h"
#include "helper.h"
/* state values */
#define _DB_STA_VALID 0xA1B2C3D4
#define _DB_STA_FREED 0x1A2B3C4D
/* the priority field is fairly simple - without any user hints, or in the case
* of a hint "tie", we give higher priority to syscalls with less chain nodes
* (filter is easier to evaluate) */
#define _DB_PRI_MASK_CHAIN 0x0000FFFF
#define _DB_PRI_MASK_USER 0x00FF0000
#define _DB_PRI_USER(x) (((x) << 16) & _DB_PRI_MASK_USER)
/* prove information about the sub-tree check results */
struct db_iter_state {
#define _DB_IST_NONE 0x00000000
#define _DB_IST_MATCH 0x00000001
#define _DB_IST_MATCH_ONCE 0x00000002
#define _DB_IST_X_FINISHED 0x00000010
#define _DB_IST_N_FINISHED 0x00000020
#define _DB_IST_X_PREFIX 0x00000100
#define _DB_IST_N_PREFIX 0x00000200
#define _DB_IST_M_MATCHSET (_DB_IST_MATCH|_DB_IST_MATCH_ONCE)
#define _DB_IST_M_REDUNDANT (_DB_IST_MATCH| \
_DB_IST_X_FINISHED| \
_DB_IST_N_PREFIX)
unsigned int flags;
uint32_t action;
struct db_sys_list *sx;
};
static unsigned int _db_node_put(struct db_arg_chain_tree **node);
/**
* Define the syscall argument priority for nodes on the same level of the tree
* @param a tree node
*
* Prioritize the syscall argument value, taking into account hi/lo words.
* Should only ever really be called by _db_chain_{lt,eq}(). Returns an
* arbitrary value indicating priority.
*
*/
static unsigned int __db_chain_arg_priority(const struct db_arg_chain_tree *a)
{
return (a->arg << 1) + (a->arg_h_flg ? 1 : 0);
}
/**
* Define the "op" priority for nodes on the same level of the tree
* @param op the argument operator
*
* Prioritize the syscall argument comparison operator. Should only ever
* really be called by _db_chain_{lt,eq}(). Returns an arbitrary value
* indicating priority.
*
*/
static unsigned int __db_chain_op_priority(enum scmp_compare op)
{
/* the distinction between LT/LT and GT/GE is mostly to make the
* ordering as repeatable as possible regardless of the order in which
* the rules are added */
switch (op) {
case SCMP_CMP_MASKED_EQ:
case SCMP_CMP_EQ:
case SCMP_CMP_NE:
return 3;
case SCMP_CMP_LE:
case SCMP_CMP_LT:
return 2;
case SCMP_CMP_GE:
case SCMP_CMP_GT:
return 1;
default:
return 0;
}
}
/**
* Determine if node "a" is less than node "b"
* @param a tree node
* @param b tree node
*
* The logic is best explained by looking at the comparison code in the
* function.
*
*/
static bool _db_chain_lt(const struct db_arg_chain_tree *a,
const struct db_arg_chain_tree *b)
{
unsigned int a_arg, b_arg;
unsigned int a_op, b_op;
a_arg = __db_chain_arg_priority(a);
b_arg = __db_chain_arg_priority(b);
if (a_arg < b_arg)
return true;
else if (a_arg > b_arg)
return false;
a_op = __db_chain_op_priority(a->op_orig);
b_op = __db_chain_op_priority(b->op_orig);
if (a_op < b_op)
return true;
else if (a_op > b_op)
return false;
/* NOTE: at this point the arg and op priorities are equal */
switch (a->op_orig) {
case SCMP_CMP_LE:
case SCMP_CMP_LT:
/* in order to ensure proper ordering for LT/LE comparisons we
* need to invert the argument value so smaller values come
* first */
if (a->datum > b->datum)
return true;
break;
default:
if (a->datum < b->datum)
return true;
break;
}
return false;
}
/**
* Determine if two nodes have equal argument datum values
* @param a tree node
* @param b tree node
*
* In order to return true the nodes must have the same datum and mask for the
* same argument.
*
*/
static bool _db_chain_eq(const struct db_arg_chain_tree *a,
const struct db_arg_chain_tree *b)
{
unsigned int a_arg, b_arg;
a_arg = __db_chain_arg_priority(a);
b_arg = __db_chain_arg_priority(b);
return ((a_arg == b_arg) && (a->op == b->op) &&
(a->datum == b->datum) && (a->mask == b->mask));
}
/**
* Determine if a given tree node is a leaf node
* @param iter the node to test
*
* A leaf node is a node with no other nodes beneath it.
*
*/
static bool _db_chain_leaf(const struct db_arg_chain_tree *iter)
{
return (iter->nxt_t == NULL && iter->nxt_f == NULL);
}
/**
* Determine if a given tree node is a zombie node
* @param iter the node to test
*
* A zombie node is a leaf node that also has no true or false actions.
*
*/
static bool _db_chain_zombie(const struct db_arg_chain_tree *iter)
{
return (_db_chain_leaf(iter) &&
!(iter->act_t_flg) && !(iter->act_f_flg));
}
/**
* Get a node reference
* @param node pointer to a node
*
* This function gets a reference to an individual node. Returns a pointer
* to the node.
*
*/
static struct db_arg_chain_tree *_db_node_get(struct db_arg_chain_tree *node)
{
if (node != NULL)
node->refcnt++;
return node;
}
/**
* Garbage collect a level of the tree
* @param node tree node
*
* Check the entire level on which @node resides, if there is no other part of
* the tree which points to a node on this level, remove the entire level.
* Returns the number of nodes removed.
*
*/
static unsigned int _db_level_clean(struct db_arg_chain_tree *node)
{
int cnt = 0;
unsigned int links;
struct db_arg_chain_tree *n = node;
struct db_arg_chain_tree *start;
while (n->lvl_prv)
n = n->lvl_prv;
start = n;
while (n != NULL) {
links = 0;
if (n->lvl_prv)
links++;
if (n->lvl_nxt)
links++;
if (n->refcnt > links)
return cnt;
n = n->lvl_nxt;
}
n = start;
while (n != NULL)
cnt += _db_node_put(&n);
return cnt;
}
/**
* Free a syscall filter argument chain tree
* @param tree the argument chain list
*
* This function drops a reference to the tree pointed to by @tree and garbage
* collects the top level. Returns the number of nodes removed.
*
*/
static unsigned int _db_tree_put(struct db_arg_chain_tree **tree)
{
unsigned int cnt;
cnt = _db_node_put(tree);
if (*tree)
cnt += _db_level_clean(*tree);
return cnt;
}
/**
* Release a node reference
* @param node pointer to a node
*
* This function drops a reference to an individual node, unless this is the
* last reference in which the entire sub-tree is affected. Returns the number
* of nodes freed.
*
*/
static unsigned int _db_node_put(struct db_arg_chain_tree **node)
{
unsigned int cnt = 0;
struct db_arg_chain_tree *n = *node;
struct db_arg_chain_tree *lvl_p, *lvl_n, *nxt_t, *nxt_f;
if (n == NULL)
return 0;
if (--(n->refcnt) == 0) {
lvl_p = n->lvl_prv;
lvl_n = n->lvl_nxt;
nxt_t = n->nxt_t;
nxt_f = n->nxt_f;
/* split the current level */
/* NOTE: we still hold a ref for both lvl_p and lvl_n */
if (lvl_p)
lvl_p->lvl_nxt = NULL;
if (lvl_n)
lvl_n->lvl_prv = NULL;
/* drop refcnts on the current level */
if (lvl_p)
cnt += _db_node_put(&lvl_p);
if (lvl_n)
cnt += _db_node_put(&lvl_n);
/* re-link current level if it still exists */
if (lvl_p)
lvl_p->lvl_nxt = _db_node_get(lvl_n);
if (lvl_n)
lvl_n->lvl_prv = _db_node_get(lvl_p);
/* update caller's pointer */
if (lvl_p)
*node = lvl_p;
else if (lvl_n)
*node = lvl_n;
else
*node = NULL;
/* drop the next level(s) */
cnt += _db_tree_put(&nxt_t);
cnt += _db_tree_put(&nxt_f);
/* cleanup and accounting */
free(n);
cnt++;
}
return cnt;
}
/**
* Remove a node from an argument chain tree
* @param tree the pointer to the tree
* @param node the node to remove
*
* This function searches the tree looking for the node and removes it as well
* as any sub-trees beneath it. Returns the number of nodes freed.
*
*/
static unsigned int _db_tree_remove(struct db_arg_chain_tree **tree,
struct db_arg_chain_tree *node)
{
int cnt = 0;
struct db_arg_chain_tree *c_iter;
if (tree == NULL || *tree == NULL || node == NULL)
return 0;
c_iter = *tree;
while (c_iter->lvl_prv != NULL)
c_iter = c_iter->lvl_prv;
do {
/* current node? */
if (c_iter == node)
goto remove;
/* check the sub-trees */
cnt += _db_tree_remove(&(c_iter->nxt_t), node);
cnt += _db_tree_remove(&(c_iter->nxt_f), node);
/* check for empty/zombie nodes */
if (_db_chain_zombie(c_iter))
goto remove;
/* next node on this level */
c_iter = c_iter->lvl_nxt;
} while (c_iter != NULL && cnt == 0);
return cnt;
remove:
/* reset the tree pointer if needed */
if (c_iter == *tree) {
if (c_iter->lvl_prv != NULL)
*tree = c_iter->lvl_prv;
else
*tree = c_iter->lvl_nxt;
}
/* remove the node from the current level */
if (c_iter->lvl_prv)
c_iter->lvl_prv->lvl_nxt = c_iter->lvl_nxt;
if (c_iter->lvl_nxt)
c_iter->lvl_nxt->lvl_prv = c_iter->lvl_prv;
c_iter->lvl_prv = NULL;
c_iter->lvl_nxt = NULL;
/* free the node and any sub-trees */
cnt += _db_node_put(&c_iter);
return cnt;
}
/**
* Traverse a tree checking the action values
* @param tree the pointer to the tree
* @param action the action
*
* Traverse the tree inspecting each action to see if it matches the given
* action. Returns zero if all actions match the given action, negative values
* on failure.
*
*/
static int _db_tree_act_check(struct db_arg_chain_tree *tree, uint32_t action)
{
int rc;
struct db_arg_chain_tree *c_iter;
if (tree == NULL)
return 0;
c_iter = tree;
while (c_iter->lvl_prv != NULL)
c_iter = c_iter->lvl_prv;
do {
if (c_iter->act_t_flg && c_iter->act_t != action)
return -EEXIST;
if (c_iter->act_f_flg && c_iter->act_f != action)
return -EEXIST;
rc = _db_tree_act_check(c_iter->nxt_t, action);
if (rc < 0)
return rc;
rc = _db_tree_act_check(c_iter->nxt_f, action);
if (rc < 0)
return rc;
c_iter = c_iter->lvl_nxt;
} while (c_iter != NULL);
return 0;
}
/**
* Checks for a sub-tree match in an existing tree and prunes the tree
* @param existing pointer to the existing tree
* @param new pointer to the new tree
* @param state pointer to a state structure
*
* This function searches the existing tree trying to prune it based on the
* new tree. Returns the number of nodes removed from the tree on success,
* zero if no changes were made.
*
*/
static int _db_tree_prune(struct db_arg_chain_tree **existing,
struct db_arg_chain_tree *new,
struct db_iter_state *state)
{
int cnt = 0;
struct db_iter_state state_nxt;
struct db_iter_state state_new = *state;
struct db_arg_chain_tree *x_iter_next;
struct db_arg_chain_tree *x_iter = *existing;
struct db_arg_chain_tree *n_iter = new;
/* check if either tree is finished */
if (n_iter == NULL || x_iter == NULL)
goto prune_return;
/* bail out if we have a broken match */
if ((state->flags & _DB_IST_M_MATCHSET) == _DB_IST_MATCH_ONCE)
goto prune_return;
/* get to the start of the existing level */
while (x_iter->lvl_prv)
x_iter = x_iter->lvl_prv;
/* NOTE: a few comments on the code below ...
* 1) we need to take a reference before we go down a level in case
* we end up dropping the sub-tree (see the _db_node_get() calls)
* 2) since the new tree really only has one branch, we can only ever
* match on one branch in the existing tree, if we "hit" then we
* can bail on the other branches */
do {
/* store this now in case we remove x_iter */
x_iter_next = x_iter->lvl_nxt;
/* compare the two nodes */
if (_db_chain_eq(x_iter, n_iter)) {
/* we have a match */
state_new.flags |= _DB_IST_M_MATCHSET;
/* check if either tree is finished */
if (_db_chain_leaf(n_iter))
state_new.flags |= _DB_IST_N_FINISHED;
if (_db_chain_leaf(x_iter))
state_new.flags |= _DB_IST_X_FINISHED;
/* don't remove nodes if we have more actions/levels */
if ((x_iter->act_t_flg || x_iter->nxt_t) &&
!(n_iter->act_t_flg || n_iter->nxt_t))
goto prune_return;
if ((x_iter->act_f_flg || x_iter->nxt_f) &&
!(n_iter->act_f_flg || n_iter->nxt_f))
goto prune_return;
/* if finished, compare actions */
if ((state_new.flags & _DB_IST_N_FINISHED) &&
(state_new.flags & _DB_IST_X_FINISHED)) {
if (n_iter->act_t_flg != x_iter->act_t_flg)
goto prune_return;
if (n_iter->act_t != x_iter->act_t)
goto prune_return;
if (n_iter->act_f_flg != x_iter->act_f_flg)
goto prune_return;
if (n_iter->act_f != x_iter->act_f)
goto prune_return;
}
/* check next level */
if (n_iter->nxt_t) {
_db_node_get(x_iter);
state_nxt = *state;
state_nxt.flags |= _DB_IST_M_MATCHSET;
cnt += _db_tree_prune(&x_iter->nxt_t,
n_iter->nxt_t,
&state_nxt);
cnt += _db_node_put(&x_iter);
if (state_nxt.flags & _DB_IST_MATCH) {
state_new.flags |= state_nxt.flags;
/* don't return yet, we need to check
* the current node */
}
if (x_iter == NULL)
goto prune_next_node;
}
if (n_iter->nxt_f) {
_db_node_get(x_iter);
state_nxt = *state;
state_nxt.flags |= _DB_IST_M_MATCHSET;
cnt += _db_tree_prune(&x_iter->nxt_f,
n_iter->nxt_f,
&state_nxt);
cnt += _db_node_put(&x_iter);
if (state_nxt.flags & _DB_IST_MATCH) {
state_new.flags |= state_nxt.flags;
/* don't return yet, we need to check
* the current node */
}
if (x_iter == NULL)
goto prune_next_node;
}
/* remove the node? */
if (!_db_tree_act_check(x_iter, state_new.action) &&
(state_new.flags & _DB_IST_MATCH) &&
(state_new.flags & _DB_IST_N_FINISHED) &&
(state_new.flags & _DB_IST_X_PREFIX)) {
/* yes - the new tree is "shorter" */
cnt += _db_tree_remove(&state->sx->chains,
x_iter);
if (state->sx->chains == NULL)
goto prune_return;
} else if (!_db_tree_act_check(x_iter, state_new.action)
&& (state_new.flags & _DB_IST_MATCH) &&
(state_new.flags & _DB_IST_X_FINISHED) &&
(state_new.flags & _DB_IST_N_PREFIX)) {
/* no - the new tree is "longer" */
goto prune_return;
}
} else if (_db_chain_lt(x_iter, n_iter)) {
/* bail if we have a prefix on the new tree */
if (state->flags & _DB_IST_N_PREFIX)
goto prune_return;
/* check the next level in the existing tree */
if (x_iter->nxt_t) {
_db_node_get(x_iter);
state_nxt = *state;
state_nxt.flags &= ~_DB_IST_MATCH;
state_nxt.flags |= _DB_IST_X_PREFIX;
cnt += _db_tree_prune(&x_iter->nxt_t, n_iter,
&state_nxt);
cnt += _db_node_put(&x_iter);
if (state_nxt.flags & _DB_IST_MATCH) {
state_new.flags |= state_nxt.flags;
goto prune_return;
}
if (x_iter == NULL)
goto prune_next_node;
}
if (x_iter->nxt_f) {
_db_node_get(x_iter);
state_nxt = *state;
state_nxt.flags &= ~_DB_IST_MATCH;
state_nxt.flags |= _DB_IST_X_PREFIX;
cnt += _db_tree_prune(&x_iter->nxt_f, n_iter,
&state_nxt);
cnt += _db_node_put(&x_iter);
if (state_nxt.flags & _DB_IST_MATCH) {
state_new.flags |= state_nxt.flags;
goto prune_return;
}
if (x_iter == NULL)
goto prune_next_node;
}
} else {
/* bail if we have a prefix on the existing tree */
if (state->flags & _DB_IST_X_PREFIX)
goto prune_return;
/* check the next level in the new tree */
if (n_iter->nxt_t) {
_db_node_get(x_iter);
state_nxt = *state;
state_nxt.flags &= ~_DB_IST_MATCH;
state_nxt.flags |= _DB_IST_N_PREFIX;
cnt += _db_tree_prune(&x_iter, n_iter->nxt_t,
&state_nxt);
cnt += _db_node_put(&x_iter);
if (state_nxt.flags & _DB_IST_MATCH) {
state_new.flags |= state_nxt.flags;
goto prune_return;
}
if (x_iter == NULL)
goto prune_next_node;
}
if (n_iter->nxt_f) {
_db_node_get(x_iter);
state_nxt = *state;
state_nxt.flags &= ~_DB_IST_MATCH;
state_nxt.flags |= _DB_IST_N_PREFIX;
cnt += _db_tree_prune(&x_iter, n_iter->nxt_f,
&state_nxt);
cnt += _db_node_put(&x_iter);
if (state_nxt.flags & _DB_IST_MATCH) {
state_new.flags |= state_nxt.flags;
goto prune_return;
}
if (x_iter == NULL)
goto prune_next_node;
}
}
prune_next_node:
/* check next node on this level */
x_iter = x_iter_next;
} while (x_iter);
/* if we are falling through, we clearly didn't match on anything */
state_new.flags &= ~_DB_IST_MATCH;
prune_return:
/* no more nodes on this level, return to the level above */
if (state_new.flags & _DB_IST_MATCH)
state->flags |= state_new.flags;
else
state->flags &= ~_DB_IST_MATCH;
return cnt;
}
/**
* Add a new tree into an existing tree
* @param existing pointer to the existing tree
* @param new pointer to the new tree
* @param state pointer to a state structure
*
* This function adds the new tree into the existing tree, fetching additional
* references as necessary. Returns zero on success, negative values on
* failure.
*
*/
static int _db_tree_add(struct db_arg_chain_tree **existing,
struct db_arg_chain_tree *new,
struct db_iter_state *state)
{
int rc;
struct db_arg_chain_tree *x_iter = *existing;
struct db_arg_chain_tree *n_iter = new;
do {
if (_db_chain_eq(x_iter, n_iter)) {
if (n_iter->act_t_flg) {
if (!x_iter->act_t_flg) {
/* new node has a true action */
/* do the actions match? */
rc = _db_tree_act_check(x_iter->nxt_t,
n_iter->act_t);
if (rc != 0)
return rc;
/* update with the new action */
rc = _db_node_put(&x_iter->nxt_t);
x_iter->nxt_t = NULL;
x_iter->act_t = n_iter->act_t;
x_iter->act_t_flg = true;
state->sx->node_cnt -= rc;
} else if (n_iter->act_t != x_iter->act_t) {
/* if we are dealing with a 64-bit
* comparison, we need to adjust our
* action based on the full 64-bit
* value to ensure we handle GT/GE
* comparisons correctly */
if (n_iter->arg_h_flg &&
(n_iter->datum_full >
x_iter->datum_full))
x_iter->act_t = n_iter->act_t;
if (_db_chain_leaf(x_iter) ||
_db_chain_leaf(n_iter))
return -EEXIST;
}
}
if (n_iter->act_f_flg) {
if (!x_iter->act_f_flg) {
/* new node has a false action */
/* do the actions match? */
rc = _db_tree_act_check(x_iter->nxt_f,
n_iter->act_f);
if (rc != 0)
return rc;
/* update with the new action */
rc = _db_node_put(&x_iter->nxt_f);
x_iter->nxt_f = NULL;
x_iter->act_f = n_iter->act_f;
x_iter->act_f_flg = true;
state->sx->node_cnt -= rc;
} else if (n_iter->act_f != x_iter->act_f) {
/* if we are dealing with a 64-bit
* comparison, we need to adjust our
* action based on the full 64-bit
* value to ensure we handle LT/LE
* comparisons correctly */
if (n_iter->arg_h_flg &&
(n_iter->datum_full <
x_iter->datum_full))
x_iter->act_t = n_iter->act_t;
if (_db_chain_leaf(x_iter) ||
_db_chain_leaf(n_iter))
return -EEXIST;
}
}
if (n_iter->nxt_t) {
if (x_iter->nxt_t) {
/* compare the next level */
rc = _db_tree_add(&x_iter->nxt_t,
n_iter->nxt_t,
state);
if (rc != 0)
return rc;
} else if (!x_iter->act_t_flg) {
/* add a new sub-tree */
x_iter->nxt_t = _db_node_get(n_iter->nxt_t);
} else
/* done - existing tree is "shorter" */
return 0;
}
if (n_iter->nxt_f) {
if (x_iter->nxt_f) {
/* compare the next level */
rc = _db_tree_add(&x_iter->nxt_f,
n_iter->nxt_f,
state);
if (rc != 0)
return rc;
} else if (!x_iter->act_f_flg) {
/* add a new sub-tree */
x_iter->nxt_f = _db_node_get(n_iter->nxt_f);
} else
/* done - existing tree is "shorter" */
return 0;
}
return 0;
} else if (!_db_chain_lt(x_iter, n_iter)) {
/* try to move along the current level */
if (x_iter->lvl_nxt == NULL) {
/* add to the end of this level */
n_iter->lvl_prv = _db_node_get(x_iter);
x_iter->lvl_nxt = _db_node_get(n_iter);
return 0;
} else
/* next */
x_iter = x_iter->lvl_nxt;
} else {
/* add before the existing node on this level*/
if (x_iter->lvl_prv != NULL) {
x_iter->lvl_prv->lvl_nxt = _db_node_get(n_iter);
n_iter->lvl_prv = x_iter->lvl_prv;
x_iter->lvl_prv = _db_node_get(n_iter);
n_iter->lvl_nxt = x_iter;
} else {
x_iter->lvl_prv = _db_node_get(n_iter);
n_iter->lvl_nxt = _db_node_get(x_iter);
}
if (*existing == x_iter) {
*existing = _db_node_get(n_iter);
_db_node_put(&x_iter);
}
return 0;
}
} while (x_iter);
return 0;
}
/**
* Free and reset the seccomp filter DB
* @param db the seccomp filter DB
*
* This function frees any existing filters and resets the filter DB to a
* default state; only the DB architecture is preserved.
*
*/
static void _db_reset(struct db_filter *db)
{
struct db_sys_list *s_iter;
struct db_api_rule_list *r_iter;
if (db == NULL)
return;
/* free any filters */
if (db->syscalls != NULL) {
s_iter = db->syscalls;
while (s_iter != NULL) {
db->syscalls = s_iter->next;
_db_tree_put(&s_iter->chains);
free(s_iter);
s_iter = db->syscalls;
}
db->syscalls = NULL;
}
db->syscall_cnt = 0;
/* free any rules */
if (db->rules != NULL) {
/* split the loop first then loop and free */
db->rules->prev->next = NULL;
r_iter = db->rules;
while (r_iter != NULL) {
db->rules = r_iter->next;
free(r_iter);
r_iter = db->rules;
}
db->rules = NULL;
}
}
/**
* Intitalize a seccomp filter DB
* @param arch the architecture definition
*
* This function initializes a seccomp filter DB and readies it for use.
* Returns a pointer to the DB on success, NULL on failure.
*
*/
static struct db_filter *_db_init(const struct arch_def *arch)
{
struct db_filter *db;
db = zmalloc(sizeof(*db));
if (db == NULL)
return NULL;
/* set the arch and reset the DB to a known state */
db->arch = arch;
_db_reset(db);
return db;
}
/**
* Destroy a seccomp filter DB
* @param db the seccomp filter DB
*
* This function destroys a seccomp filter DB. After calling this function,
* the filter should no longer be referenced.
*
*/
static void _db_release(struct db_filter *db)
{
if (db == NULL)
return;
/* free and reset the DB */
_db_reset(db);
free(db);
}
/**
* Destroy a seccomp filter snapshot
* @param snap the seccomp filter snapshot
*
* This function destroys a seccomp filter snapshot. After calling this
* function, the snapshot should no longer be referenced.
*
*/
static void _db_snap_release(struct db_filter_snap *snap)
{
unsigned int iter;
if (snap == NULL)
return;
if (snap->filter_cnt > 0) {
for (iter = 0; iter < snap->filter_cnt; iter++) {
if (snap->filters[iter])
_db_release(snap->filters[iter]);
}
free(snap->filters);
}
free(snap);
}
/**
* Update the user specified portion of the syscall priority
* @param db the seccomp filter db
* @param syscall the syscall number
* @param priority the syscall priority
*
* This function sets, or updates, the syscall priority; the highest priority
* value between the existing and specified value becomes the new syscall
* priority. If the syscall entry does not already exist, a new phantom
* syscall entry is created as a placeholder. Returns zero on success,
* negative values on failure.
*
*/
static int _db_syscall_priority(struct db_filter *db,
int syscall, uint8_t priority)
{
unsigned int sys_pri = _DB_PRI_USER(priority);
struct db_sys_list *s_new, *s_iter, *s_prev = NULL;
assert(db != NULL);
s_iter = db->syscalls;
while (s_iter != NULL && s_iter->num < syscall) {
s_prev = s_iter;
s_iter = s_iter->next;
}
/* matched an existing syscall entry */
if (s_iter != NULL && s_iter->num == syscall) {
if (sys_pri > (s_iter->priority & _DB_PRI_MASK_USER)) {
s_iter->priority &= (~_DB_PRI_MASK_USER);
s_iter->priority |= sys_pri;
}
return 0;
}
/* no existing syscall entry - create a phantom entry */
s_new = zmalloc(sizeof(*s_new));
if (s_new == NULL)
return -ENOMEM;
s_new->num = syscall;
s_new->priority = sys_pri;
s_new->valid = false;
/* add it before s_iter */
if (s_prev != NULL) {
s_new->next = s_prev->next;
s_prev->next = s_new;
} else {
s_new->next = db->syscalls;
db->syscalls = s_new;
}
return 0;
}
/**
* Create a new rule
* @param strict the strict value
* @param action the rule's action
* @param syscall the syscall number
* @param chain the syscall argument filter
*
* This function creates a new rule structure based on the given arguments.
* Returns a pointer to the new rule on success, NULL on failure.
*
*/
static struct db_api_rule_list *_db_rule_new(bool strict,
uint32_t action, int syscall,
struct db_api_arg *chain)
{
struct db_api_rule_list *rule;
rule = zmalloc(sizeof(*rule));