* [PATCH v4 1/3] selinux: refactor avtab_node comparisons
2023-11-02 15:45 [PATCH v4 0/3] selinux: avtab arrays and refactors Jacob Satterfield
@ 2023-11-02 15:45 ` Jacob Satterfield
2023-11-02 15:45 ` [PATCH v4 2/3] selinux: fix conditional avtab slot hint Jacob Satterfield
2023-11-02 15:45 ` [PATCH v4 3/3] selinux: use arrays for avtab hashtable nodes Jacob Satterfield
2 siblings, 0 replies; 6+ messages in thread
From: Jacob Satterfield @ 2023-11-02 15:45 UTC (permalink / raw)
To: selinux; +Cc: Jacob Satterfield, stephen.smalley.work, paul, omosnace
In four separate functions within avtab, the same comparison logic is
used. The only difference is how the result is handled or whether there
is a unique specifier value to be checked for or used.
Extracting this functionality into the avtab_node_cmp() function unifies
the comparison logic between searching and insertion and gets rid of
duplicative code so that the implementation is easier to maintain.
Signed-off-by: Jacob Satterfield <jsatterfield.linux@gmail.com>
Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com>
---
security/selinux/ss/avtab.c | 101 +++++++++++++++---------------------
1 file changed, 41 insertions(+), 60 deletions(-)
diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index 8751a602ead2..697eb4352439 100644
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -96,12 +96,34 @@ avtab_insert_node(struct avtab *h, struct avtab_node **dst,
return newnode;
}
+static int avtab_node_cmp(const struct avtab_key *key1,
+ const struct avtab_key *key2)
+{
+ u16 specified = key1->specified & ~(AVTAB_ENABLED|AVTAB_ENABLED_OLD);
+
+ if (key1->source_type == key2->source_type &&
+ key1->target_type == key2->target_type &&
+ key1->target_class == key2->target_class &&
+ (specified & key2->specified))
+ return 0;
+ if (key1->source_type < key2->source_type)
+ return -1;
+ if (key1->source_type == key2->source_type &&
+ key1->target_type < key2->target_type)
+ return -1;
+ if (key1->source_type == key2->source_type &&
+ key1->target_type == key2->target_type &&
+ key1->target_class < key2->target_class)
+ return -1;
+ return 1;
+}
+
static int avtab_insert(struct avtab *h, const struct avtab_key *key,
const struct avtab_datum *datum)
{
u32 hvalue;
struct avtab_node *prev, *cur, *newnode;
- u16 specified = key->specified & ~(AVTAB_ENABLED|AVTAB_ENABLED_OLD);
+ int cmp;
if (!h || !h->nslot || h->nel == U32_MAX)
return -EINVAL;
@@ -110,23 +132,11 @@ static int avtab_insert(struct avtab *h, const struct avtab_key *key,
for (prev = NULL, cur = h->htable[hvalue];
cur;
prev = cur, cur = cur->next) {
- if (key->source_type == cur->key.source_type &&
- key->target_type == cur->key.target_type &&
- key->target_class == cur->key.target_class &&
- (specified & cur->key.specified)) {
- /* extended perms may not be unique */
- if (specified & AVTAB_XPERMS)
- break;
+ cmp = avtab_node_cmp(key, &cur->key);
+ /* extended perms may not be unique */
+ if (cmp == 0 && !(key->specified & AVTAB_XPERMS))
return -EEXIST;
- }
- if (key->source_type < cur->key.source_type)
- break;
- if (key->source_type == cur->key.source_type &&
- key->target_type < cur->key.target_type)
- break;
- if (key->source_type == cur->key.source_type &&
- key->target_type == cur->key.target_type &&
- key->target_class < cur->key.target_class)
+ if (cmp <= 0)
break;
}
@@ -148,7 +158,7 @@ struct avtab_node *avtab_insert_nonunique(struct avtab *h,
{
u32 hvalue;
struct avtab_node *prev, *cur;
- u16 specified = key->specified & ~(AVTAB_ENABLED|AVTAB_ENABLED_OLD);
+ int cmp;
if (!h || !h->nslot || h->nel == U32_MAX)
return NULL;
@@ -156,19 +166,8 @@ struct avtab_node *avtab_insert_nonunique(struct avtab *h,
for (prev = NULL, cur = h->htable[hvalue];
cur;
prev = cur, cur = cur->next) {
- if (key->source_type == cur->key.source_type &&
- key->target_type == cur->key.target_type &&
- key->target_class == cur->key.target_class &&
- (specified & cur->key.specified))
- break;
- if (key->source_type < cur->key.source_type)
- break;
- if (key->source_type == cur->key.source_type &&
- key->target_type < cur->key.target_type)
- break;
- if (key->source_type == cur->key.source_type &&
- key->target_type == cur->key.target_type &&
- key->target_class < cur->key.target_class)
+ cmp = avtab_node_cmp(key, &cur->key);
+ if (cmp <= 0)
break;
}
return avtab_insert_node(h, prev ? &prev->next : &h->htable[hvalue],
@@ -183,7 +182,7 @@ struct avtab_node *avtab_search_node(struct avtab *h,
{
u32 hvalue;
struct avtab_node *cur;
- u16 specified = key->specified & ~(AVTAB_ENABLED|AVTAB_ENABLED_OLD);
+ int cmp;
if (!h || !h->nslot)
return NULL;
@@ -191,20 +190,10 @@ struct avtab_node *avtab_search_node(struct avtab *h,
hvalue = avtab_hash(key, h->mask);
for (cur = h->htable[hvalue]; cur;
cur = cur->next) {
- if (key->source_type == cur->key.source_type &&
- key->target_type == cur->key.target_type &&
- key->target_class == cur->key.target_class &&
- (specified & cur->key.specified))
+ cmp = avtab_node_cmp(key, &cur->key);
+ if (cmp == 0)
return cur;
-
- if (key->source_type < cur->key.source_type)
- break;
- if (key->source_type == cur->key.source_type &&
- key->target_type < cur->key.target_type)
- break;
- if (key->source_type == cur->key.source_type &&
- key->target_type == cur->key.target_type &&
- key->target_class < cur->key.target_class)
+ if (cmp < 0)
break;
}
return NULL;
@@ -213,27 +202,19 @@ struct avtab_node *avtab_search_node(struct avtab *h,
struct avtab_node*
avtab_search_node_next(struct avtab_node *node, u16 specified)
{
+ struct avtab_key tmp_key;
struct avtab_node *cur;
+ int cmp;
if (!node)
return NULL;
-
- specified &= ~(AVTAB_ENABLED|AVTAB_ENABLED_OLD);
+ tmp_key = node->key;
+ tmp_key.specified = specified;
for (cur = node->next; cur; cur = cur->next) {
- if (node->key.source_type == cur->key.source_type &&
- node->key.target_type == cur->key.target_type &&
- node->key.target_class == cur->key.target_class &&
- (specified & cur->key.specified))
+ cmp = avtab_node_cmp(&tmp_key, &cur->key);
+ if (cmp == 0)
return cur;
-
- if (node->key.source_type < cur->key.source_type)
- break;
- if (node->key.source_type == cur->key.source_type &&
- node->key.target_type < cur->key.target_type)
- break;
- if (node->key.source_type == cur->key.source_type &&
- node->key.target_type == cur->key.target_type &&
- node->key.target_class < cur->key.target_class)
+ if (cmp < 0)
break;
}
return NULL;
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v4 2/3] selinux: fix conditional avtab slot hint
2023-11-02 15:45 [PATCH v4 0/3] selinux: avtab arrays and refactors Jacob Satterfield
2023-11-02 15:45 ` [PATCH v4 1/3] selinux: refactor avtab_node comparisons Jacob Satterfield
@ 2023-11-02 15:45 ` Jacob Satterfield
2023-11-02 15:45 ` [PATCH v4 3/3] selinux: use arrays for avtab hashtable nodes Jacob Satterfield
2 siblings, 0 replies; 6+ messages in thread
From: Jacob Satterfield @ 2023-11-02 15:45 UTC (permalink / raw)
To: selinux; +Cc: Jacob Satterfield, stephen.smalley.work, paul, omosnace
Due to how conditional rules are written in the binary policy, the
code responsible for loading does not know how many conditional rules
there are before creating the avtab structure. Instead, it uses the
number of elements in the non-conditional avtab as a hint and allocates
the hash table based on it. In the refpolicy and default Fedora policy,
the actual sizes of these tables are not similar (~85k vs ~10k) thereby
creating more slots than needed and resulting in wasted memory.
This patch introduces a two-pass algorithm to calculate the conditional
rule count before allocating the avtab nodes array. Albeit with a slight
performance penalty in reading a portion of the binary policy twice,
this causes the number of hash slots for the conditional array to become
4096 instead of 32768. At 8-bytes per slot on 64-bit architectures, this
results in a net savings of 224 KB of heap memory.
Signed-off-by: Jacob Satterfield <jsatterfield.linux@gmail.com>
---
security/selinux/ss/avtab.c | 15 ++++++++++--
security/selinux/ss/avtab.h | 2 +-
security/selinux/ss/conditional.c | 38 ++++++++++++++++++++-----------
security/selinux/ss/conditional.h | 2 +-
4 files changed, 40 insertions(+), 17 deletions(-)
diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index 672a524e6dee..f437bd588b04 100644
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -338,7 +338,7 @@ static const uint16_t spec_order[] = {
int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
int (*insertf)(struct avtab *a, const struct avtab_key *k,
const struct avtab_datum *d, void *p),
- void *p)
+ void *p, u32 *nrules)
{
__le16 buf16[4];
u16 enabled;
@@ -412,6 +412,11 @@ int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
if (val & spec_order[i]) {
key.specified = spec_order[i] | enabled;
datum.u.data = le32_to_cpu(buf32[items++]);
+ /* first pass of conditional table read */
+ if (nrules) {
+ (*nrules)++;
+ continue;
+ }
rc = insertf(a, &key, &datum, p);
if (rc)
return rc;
@@ -490,6 +495,12 @@ int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
pr_err("SELinux: avtab: invalid type\n");
return -EINVAL;
}
+
+ /* first pass of conditional table read */
+ if (nrules) {
+ (*nrules)++;
+ return 0;
+ }
return insertf(a, &key, &datum, p);
}
@@ -523,7 +534,7 @@ int avtab_read(struct avtab *a, void *fp, struct policydb *pol)
goto bad;
for (i = 0; i < nel; i++) {
- rc = avtab_read_item(a, fp, pol, avtab_insertf, NULL);
+ rc = avtab_read_item(a, fp, pol, avtab_insertf, NULL, NULL);
if (rc) {
if (rc == -ENOMEM)
pr_err("SELinux: avtab: out of memory\n");
diff --git a/security/selinux/ss/avtab.h b/security/selinux/ss/avtab.h
index 3c3904bf02b0..86fb6f793eec 100644
--- a/security/selinux/ss/avtab.h
+++ b/security/selinux/ss/avtab.h
@@ -104,7 +104,7 @@ struct policydb;
int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
int (*insert)(struct avtab *a, const struct avtab_key *k,
const struct avtab_datum *d, void *p),
- void *p);
+ void *p, u32 *nrules);
int avtab_read(struct avtab *a, void *fp, struct policydb *pol);
int avtab_write_item(struct policydb *p, const struct avtab_node *cur, void *fp);
diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index 81ff676f209a..810319bf0e60 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -321,9 +321,9 @@ static int cond_insertf(struct avtab *a, const struct avtab_key *k,
return 0;
}
-static int cond_read_av_list(struct policydb *p, void *fp,
+static int cond_read_av_list(struct policydb *p, struct policy_file *fp,
struct cond_av_list *list,
- struct cond_av_list *other)
+ struct cond_av_list *other, u32 *nrules)
{
int rc;
__le32 buf[1];
@@ -347,7 +347,7 @@ static int cond_read_av_list(struct policydb *p, void *fp,
for (i = 0; i < len; i++) {
data.dst = &list->nodes[i];
rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
- &data);
+ &data, nrules);
if (rc) {
kfree(list->nodes);
list->nodes = NULL;
@@ -373,7 +373,8 @@ static int expr_node_isvalid(struct policydb *p, struct cond_expr_node *expr)
return 1;
}
-static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
+static int cond_read_node(struct policydb *p, struct cond_node *node,
+ struct policy_file *fp, u32 *nrules)
{
__le32 buf[2];
u32 i, len;
@@ -407,16 +408,17 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
return -EINVAL;
}
- rc = cond_read_av_list(p, fp, &node->true_list, NULL);
+ rc = cond_read_av_list(p, fp, &node->true_list, NULL, nrules);
if (rc)
return rc;
- return cond_read_av_list(p, fp, &node->false_list, &node->true_list);
+ return cond_read_av_list(p, fp, &node->false_list, &node->true_list, nrules);
}
-int cond_read_list(struct policydb *p, void *fp)
+int cond_read_list(struct policydb *p, struct policy_file *fp)
{
__le32 buf[1];
- u32 i, len;
+ struct policy_file tmp_fp;
+ u32 i, len, nrules;
int rc;
rc = next_entry(buf, fp, sizeof(buf));
@@ -428,15 +430,25 @@ int cond_read_list(struct policydb *p, void *fp)
p->cond_list = kcalloc(len, sizeof(*p->cond_list), GFP_KERNEL);
if (!p->cond_list)
return -ENOMEM;
+ p->cond_list_len = len;
+
+ /* first pass to only calculate the avrule count */
+ tmp_fp = *fp;
+ nrules = 0;
+ for (i = 0; i < p->cond_list_len; i++) {
+ rc = cond_read_node(p, &p->cond_list[i], &tmp_fp, &nrules);
+ if (rc)
+ goto err;
+ cond_node_destroy(&p->cond_list[i]);
+ }
- rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
+ rc = avtab_alloc(&(p->te_cond_avtab), nrules);
if (rc)
goto err;
- p->cond_list_len = len;
-
- for (i = 0; i < len; i++) {
- rc = cond_read_node(p, &p->cond_list[i], fp);
+ /* second pass to read in the conditional nodes */
+ for (i = 0; i < p->cond_list_len; i++) {
+ rc = cond_read_node(p, &p->cond_list[i], fp, NULL);
if (rc)
goto err;
}
diff --git a/security/selinux/ss/conditional.h b/security/selinux/ss/conditional.h
index 5a7b51278dc6..62a12d00cac9 100644
--- a/security/selinux/ss/conditional.h
+++ b/security/selinux/ss/conditional.h
@@ -70,7 +70,7 @@ int cond_destroy_bool(void *key, void *datum, void *p);
int cond_index_bool(void *key, void *datum, void *datap);
int cond_read_bool(struct policydb *p, struct symtab *s, void *fp);
-int cond_read_list(struct policydb *p, void *fp);
+int cond_read_list(struct policydb *p, struct policy_file *fp);
int cond_write_bool(void *key, void *datum, void *ptr);
int cond_write_list(struct policydb *p, void *fp);
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v4 3/3] selinux: use arrays for avtab hashtable nodes
2023-11-02 15:45 [PATCH v4 0/3] selinux: avtab arrays and refactors Jacob Satterfield
2023-11-02 15:45 ` [PATCH v4 1/3] selinux: refactor avtab_node comparisons Jacob Satterfield
2023-11-02 15:45 ` [PATCH v4 2/3] selinux: fix conditional avtab slot hint Jacob Satterfield
@ 2023-11-02 15:45 ` Jacob Satterfield
2023-11-02 17:34 ` Stephen Smalley
2 siblings, 1 reply; 6+ messages in thread
From: Jacob Satterfield @ 2023-11-02 15:45 UTC (permalink / raw)
To: selinux; +Cc: Jacob Satterfield, stephen.smalley.work, paul, omosnace
The current avtab hashtable employs a separate chaining collision
resolution strategy where each bucket/chain holds an ordered linked list
of pointers to kmem_cache allocated avtab_node elements.
On Fedora 38 (x86_64) using the default policy, avtab_node_cachep
uses 573 slabs each containing 170 objects totaling 2,337,840 bytes.
A call to kmem_cache_zalloc() is required for every single rule, which
in the default policy is currently 96,730 and continually rising.
When both sets of avtab_node (regular and cond.) are turned into arrays
with the hash table chain heads pointing into it, this results in only
two additional kvcalloc() calls and the complete removal of the
kmem_cache itself and its memory and runtime overheads.
Running "perf stat -r 100 -d load_policy" has shown a runtime reduction
of around 10% on a Fedora 38 x86_64 VM with this single patch. Future
patches focused on improving the hash table's collision resolution
strategy and array layout (struct-of-arrays vs. array-of-structs) may
elicit even more caching and therefore runtime performance improvements.
To prevent the conditional table from under-allocating the avtab_node
array, which creates a heap-overflow bug, the two-pass algorithm in the
patch "selinux: fix conditional avtab slot hint" is required.
Signed-off-by: Jacob Satterfield <jsatterfield.linux@gmail.com>
---
security/selinux/ss/avtab.c | 36 ++++++++++++++++++++----------------
security/selinux/ss/avtab.h | 2 ++
2 files changed, 22 insertions(+), 16 deletions(-)
diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index f437bd588b04..50c8db8eb511 100644
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -24,7 +24,6 @@
#include "avtab.h"
#include "policydb.h"
-static struct kmem_cache *avtab_node_cachep __ro_after_init;
static struct kmem_cache *avtab_xperms_cachep __ro_after_init;
#define avtab_chain_for_each(pos, tab, slot) \
@@ -79,17 +78,15 @@ avtab_insert_node(struct avtab *h, struct avtab_node **dst,
{
struct avtab_node *newnode;
struct avtab_extended_perms *xperms;
- newnode = kmem_cache_zalloc(avtab_node_cachep, GFP_KERNEL);
- if (newnode == NULL)
+ if (h->nel == h->nnodes)
return NULL;
+ newnode = &h->nodes[h->nel];
newnode->key = *key;
if (key->specified & AVTAB_XPERMS) {
xperms = kmem_cache_zalloc(avtab_xperms_cachep, GFP_KERNEL);
- if (xperms == NULL) {
- kmem_cache_free(avtab_node_cachep, newnode);
+ if (xperms == NULL)
return NULL;
- }
*xperms = *(datum->u.xperms);
newnode->datum.u.xperms = xperms;
} else {
@@ -225,7 +222,7 @@ void avtab_destroy(struct avtab *h)
u32 i;
struct avtab_node *cur, *temp;
- if (!h)
+ if (!h || !h->htable)
return;
for (i = 0; i < h->nslot; i++) {
@@ -236,11 +233,13 @@ void avtab_destroy(struct avtab *h)
if (temp->key.specified & AVTAB_XPERMS)
kmem_cache_free(avtab_xperms_cachep,
temp->datum.u.xperms);
- kmem_cache_free(avtab_node_cachep, temp);
}
}
kvfree(h->htable);
+ kvfree(h->nodes);
h->htable = NULL;
+ h->nodes = NULL;
+ h->nnodes = 0;
h->nel = 0;
h->nslot = 0;
h->mask = 0;
@@ -249,20 +248,28 @@ void avtab_destroy(struct avtab *h)
void avtab_init(struct avtab *h)
{
h->htable = NULL;
+ h->nodes = NULL;
+ h->nnodes = 0;
h->nel = 0;
h->nslot = 0;
h->mask = 0;
}
-static int avtab_alloc_common(struct avtab *h, u32 nslot)
+static int avtab_alloc_common(struct avtab *h, u32 nslot, u32 nrules)
{
if (!nslot)
return 0;
- h->htable = kvcalloc(nslot, sizeof(void *), GFP_KERNEL);
+ h->htable = kvcalloc(nslot, sizeof(*h->htable), GFP_KERNEL);
if (!h->htable)
return -ENOMEM;
-
+ h->nodes = kvcalloc(nrules, sizeof(*h->nodes), GFP_KERNEL);
+ if (!h->nodes) {
+ kvfree(h->htable);
+ h->htable = NULL;
+ return -ENOMEM;
+ }
+ h->nnodes = nrules;
h->nslot = nslot;
h->mask = nslot - 1;
return 0;
@@ -278,7 +285,7 @@ int avtab_alloc(struct avtab *h, u32 nrules)
if (nslot > MAX_AVTAB_HASH_BUCKETS)
nslot = MAX_AVTAB_HASH_BUCKETS;
- rc = avtab_alloc_common(h, nslot);
+ rc = avtab_alloc_common(h, nslot, nrules);
if (rc)
return rc;
}
@@ -289,7 +296,7 @@ int avtab_alloc(struct avtab *h, u32 nrules)
int avtab_alloc_dup(struct avtab *new, const struct avtab *orig)
{
- return avtab_alloc_common(new, orig->nslot);
+ return avtab_alloc_common(new, orig->nslot, orig->nel);
}
#ifdef CONFIG_SECURITY_SELINUX_DEBUG
@@ -614,9 +621,6 @@ int avtab_write(struct policydb *p, struct avtab *a, void *fp)
void __init avtab_cache_init(void)
{
- avtab_node_cachep = kmem_cache_create("avtab_node",
- sizeof(struct avtab_node),
- 0, SLAB_PANIC, NULL);
avtab_xperms_cachep = kmem_cache_create("avtab_extended_perms",
sizeof(struct avtab_extended_perms),
0, SLAB_PANIC, NULL);
diff --git a/security/selinux/ss/avtab.h b/security/selinux/ss/avtab.h
index 86fb6f793eec..5e465be6f057 100644
--- a/security/selinux/ss/avtab.h
+++ b/security/selinux/ss/avtab.h
@@ -82,6 +82,8 @@ struct avtab_node {
struct avtab {
struct avtab_node **htable;
+ struct avtab_node *nodes;
+ u32 nnodes; /* number of nodes */
u32 nel; /* number of elements */
u32 nslot; /* number of hash slots */
u32 mask; /* mask to compute hash func */
--
2.34.1
^ permalink raw reply related [flat|nested] 6+ messages in thread