From ba39db6e0519aa8362dbda6523ceb69349a18dc3 Mon Sep 17 00:00:00 2001 From: Stephen Smalley Date: Tue, 24 Mar 2015 16:54:16 -0400 Subject: selinux: convert avtab hash table to flex_array Previously we shrank the avtab max hash buckets to avoid high order memory allocations, but this causes avtab lookups to degenerate to very long linear searches for the Fedora policy. Convert to using a flex_array instead so that we can increase the buckets without such limitations. This change does not alter the max hash buckets; that is left to a separate follow-on change. Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore --- security/selinux/ss/avtab.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) (limited to 'security/selinux/ss/avtab.c') diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c index a3dd9faa19c0..3ea0198fc964 100644 --- a/security/selinux/ss/avtab.c +++ b/security/selinux/ss/avtab.c @@ -46,8 +46,12 @@ avtab_insert_node(struct avtab *h, int hvalue, newnode->next = prev->next; prev->next = newnode; } else { - newnode->next = h->htable[hvalue]; - h->htable[hvalue] = newnode; + newnode->next = flex_array_get_ptr(h->htable, hvalue); + if (flex_array_put_ptr(h->htable, hvalue, newnode, + GFP_KERNEL|__GFP_ZERO)) { + kmem_cache_free(avtab_node_cachep, newnode); + return NULL; + } } h->nel++; @@ -64,7 +68,7 @@ static int avtab_insert(struct avtab *h, struct avtab_key *key, struct avtab_dat return -EINVAL; hvalue = avtab_hash(key, h->mask); - for (prev = NULL, cur = h->htable[hvalue]; + for (prev = NULL, cur = flex_array_get_ptr(h->htable, hvalue); cur; prev = cur, cur = cur->next) { if (key->source_type == cur->key.source_type && @@ -104,7 +108,7 @@ avtab_insert_nonunique(struct avtab *h, struct avtab_key *key, struct avtab_datu if (!h || !h->htable) return NULL; hvalue = avtab_hash(key, h->mask); - for (prev = NULL, cur = h->htable[hvalue]; + for (prev = NULL, cur = flex_array_get_ptr(h->htable, hvalue); cur; prev = cur, cur = cur->next) { if (key->source_type == cur->key.source_type && @@ -135,7 +139,8 @@ struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *key) return NULL; hvalue = avtab_hash(key, h->mask); - for (cur = h->htable[hvalue]; cur; cur = cur->next) { + for (cur = flex_array_get_ptr(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 && @@ -170,7 +175,8 @@ avtab_search_node(struct avtab *h, struct avtab_key *key) return NULL; hvalue = avtab_hash(key, h->mask); - for (cur = h->htable[hvalue]; cur; cur = cur->next) { + for (cur = flex_array_get_ptr(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 && @@ -228,15 +234,14 @@ void avtab_destroy(struct avtab *h) return; for (i = 0; i < h->nslot; i++) { - cur = h->htable[i]; + cur = flex_array_get_ptr(h->htable, i); while (cur) { temp = cur; cur = cur->next; kmem_cache_free(avtab_node_cachep, temp); } - h->htable[i] = NULL; } - kfree(h->htable); + flex_array_free(h->htable); h->htable = NULL; h->nslot = 0; h->mask = 0; @@ -270,7 +275,8 @@ int avtab_alloc(struct avtab *h, u32 nrules) nslot = MAX_AVTAB_HASH_BUCKETS; mask = nslot - 1; - h->htable = kcalloc(nslot, sizeof(*(h->htable)), GFP_KERNEL); + h->htable = flex_array_alloc(sizeof(struct avtab_node *), nslot, + GFP_KERNEL | __GFP_ZERO); if (!h->htable) return -ENOMEM; @@ -293,7 +299,7 @@ void avtab_hash_eval(struct avtab *h, char *tag) max_chain_len = 0; chain2_len_sum = 0; for (i = 0; i < h->nslot; i++) { - cur = h->htable[i]; + cur = flex_array_get_ptr(h->htable, i); if (cur) { slots_used++; chain_len = 0; @@ -534,7 +540,8 @@ int avtab_write(struct policydb *p, struct avtab *a, void *fp) return rc; for (i = 0; i < a->nslot; i++) { - for (cur = a->htable[i]; cur; cur = cur->next) { + for (cur = flex_array_get_ptr(a->htable, i); cur; + cur = cur->next) { rc = avtab_write_item(p, cur, fp); if (rc) return rc; -- cgit v1.2.3 From 33ebc1932a07efd8728975750409741940334489 Mon Sep 17 00:00:00 2001 From: John Brooks Date: Tue, 24 Mar 2015 16:54:17 -0400 Subject: selinux: Use a better hash function for avtab This function, based on murmurhash3, has much better distribution than the original. Using the current default of 2048 buckets, there are many fewer collisions: Before: 101421 entries and 2048/2048 buckets used, longest chain length 374 After: 101421 entries and 2048/2048 buckets used, longest chain length 81 The difference becomes much more significant when buckets are increased. A naive attempt to expand the current function to larger outputs doesn't yield any significant improvement; so this function is a prerequisite for increasing the bucket size. sds: Adapted from the original patches for libsepol to the kernel. Signed-off-by: John Brooks Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore --- security/selinux/ss/avtab.c | 41 +++++++++++++++++++++++++++++++++++++---- security/selinux/ss/avtab.h | 2 +- 2 files changed, 38 insertions(+), 5 deletions(-) (limited to 'security/selinux/ss/avtab.c') diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c index 3ea0198fc964..b64f2772b030 100644 --- a/security/selinux/ss/avtab.c +++ b/security/selinux/ss/avtab.c @@ -25,10 +25,43 @@ static struct kmem_cache *avtab_node_cachep; -static inline int avtab_hash(struct avtab_key *keyp, u16 mask) +/* Based on MurmurHash3, written by Austin Appleby and placed in the + * public domain. + */ +static inline int avtab_hash(struct avtab_key *keyp, u32 mask) { - return ((keyp->target_class + (keyp->target_type << 2) + - (keyp->source_type << 9)) & mask); + static const u32 c1 = 0xcc9e2d51; + static const u32 c2 = 0x1b873593; + static const u32 r1 = 15; + static const u32 r2 = 13; + static const u32 m = 5; + static const u32 n = 0xe6546b64; + + u32 hash = 0; + +#define mix(input) { \ + u32 v = input; \ + v *= c1; \ + v = (v << r1) | (v >> (32 - r1)); \ + v *= c2; \ + hash ^= v; \ + hash = (hash << r2) | (hash >> (32 - r2)); \ + hash = hash * m + n; \ +} + + mix(keyp->target_class); + mix(keyp->target_type); + mix(keyp->source_type); + +#undef mix + + hash ^= hash >> 16; + hash *= 0x85ebca6b; + hash ^= hash >> 13; + hash *= 0xc2b2ae35; + hash ^= hash >> 16; + + return hash & mask; } static struct avtab_node* @@ -256,7 +289,7 @@ int avtab_init(struct avtab *h) int avtab_alloc(struct avtab *h, u32 nrules) { - u16 mask = 0; + u32 mask = 0; u32 shift = 0; u32 work = nrules; u32 nslot = 0; diff --git a/security/selinux/ss/avtab.h b/security/selinux/ss/avtab.h index 9318b2b8f6c9..6d794a2eee57 100644 --- a/security/selinux/ss/avtab.h +++ b/security/selinux/ss/avtab.h @@ -56,7 +56,7 @@ struct avtab { struct flex_array *htable; u32 nel; /* number of elements */ u32 nslot; /* number of hash slots */ - u16 mask; /* mask to compute hash func */ + u32 mask; /* mask to compute hash func */ }; -- cgit v1.2.3