On Wed, Oct 30, 2019 at 7:57 PM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > > On 10/30/19 2:33 PM, Jeffrey Vander Stoep wrote: > > On Wed, Oct 30, 2019 at 7:06 PM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > >> > >> On 10/30/19 6:19 AM, Jeff Vander Stoep wrote: > >>> This replaces the reverse table lookup and reverse cache with a > >>> hashtable which improves cache-miss reverese-lookup times from > >>> O(n) to O(1) and maintains the same performance as a reverse > >>> cache hit. > >>> > >>> This reduces the time needed to add a new sidtab entry from ~500us > >>> to 5us on a Pixel 3 when there are ~10,000 sidtab entries. > >>> > >>> The implementation uses the kernel's generic hashtable API, > >>> It uses the context's string represtation as the hash source, > >>> and the kernels generic string hashing algorithm full_name_hash() > >>> to reduce the string to a 32 bit value. > >>> > >>> This change also maintains the improvement introduced in commit > >>> ee1a84fd which removed the need to keep the current sidtab locked > >>> during policy reload. It does however introduce periodic locking of > >>> the target sidtab while converting the hashtable. Sidtab entries > >>> are never modified or removed, so the context struct stored in the > >>> sid_to_context tree can also be used for the context_to_sid > >>> hashtable to reduce memory usage. > >>> > >>> This bug was reported by: > >>> - Stephen Smally on the selinux bug tracker. > >>> BUG: kernel softlockup due to too many SIDs/contexts #37 > >>> https://github.com/SELinuxProject/selinux-kernel/issues/37 > >>> - Jovana Knezevic on Android's bugtracker. > >>> Bug: 140252993 > >>> "During multi-user performance testing, we create and remove users > >>> many times. selinux_android_restorecon_pkgdir goes from 1ms to over > >>> 20ms after about 200 user creations and removals. Accumulated over > >>> ~280 packages, that adds a significant time to user creation, > >>> making perf benchmarks unreliable." > >>> > >>> Signed-off-by: Jeff Vander Stoep <jeffv@xxxxxxxxxx> > >>> Reported-by: Stephen Smalley <sds@xxxxxxxxxxxxx> > >>> Reported-by: Jovana Knezevic <jovanak@xxxxxxxxxx> > >>> --- > >>> security/selinux/include/security.h | 1 + > >>> security/selinux/selinuxfs.c | 27 +++ > >>> security/selinux/ss/context.h | 9 + > >>> security/selinux/ss/policydb.c | 5 + > >>> security/selinux/ss/services.c | 81 +++++--- > >>> security/selinux/ss/services.h | 4 +- > >>> security/selinux/ss/sidtab.c | 283 ++++++++++++++++------------ > >>> security/selinux/ss/sidtab.h | 20 +- > >>> 8 files changed, 283 insertions(+), 147 deletions(-) > >>> > >>> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h > >>> index ae840634e3c7..8c0dbbd076c6 100644 > >>> --- a/security/selinux/include/security.h > >>> +++ b/security/selinux/include/security.h > >>> @@ -395,5 +395,6 @@ extern int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm); > >>> extern void avtab_cache_init(void); > >>> extern void ebitmap_cache_init(void); > >>> extern void hashtab_cache_init(void); > >>> +extern int security_sidtab_hash_stats(struct selinux_state *state, char *page); > >>> > >>> #endif /* _SELINUX_SECURITY_H_ */ > >>> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c > >>> index ee94fa469c29..ebdec88d9ccb 100644 > >>> --- a/security/selinux/selinuxfs.c > >>> +++ b/security/selinux/selinuxfs.c > >>> @@ -1482,6 +1482,32 @@ static ssize_t sel_read_avc_hash_stats(struct file *filp, char __user *buf, > >>> return length; > >>> } > >>> > >>> +static ssize_t sel_read_sidtab_hash_stats(struct file *filp, char __user *buf, > >>> + size_t count, loff_t *ppos) > >>> +{ > >>> + struct selinux_fs_info *fsi = file_inode(filp)->i_sb->s_fs_info; > >>> + struct selinux_state *state = fsi->state; > >>> + char *page; > >>> + ssize_t length; > >>> + > >>> + page = (char *)__get_free_page(GFP_KERNEL); > >>> + if (!page) > >>> + return -ENOMEM; > >>> + > >>> + length = security_sidtab_hash_stats(state, page); > >>> + if (length >= 0) > >>> + length = simple_read_from_buffer(buf, count, ppos, page, > >>> + length); > >>> + free_page((unsigned long)page); > >>> + > >>> + return length; > >>> +} > >>> + > >>> +static const struct file_operations sel_sidtab_hash_stats_ops = { > >>> + .read = sel_read_sidtab_hash_stats, > >>> + .llseek = generic_file_llseek, > >>> +}; > >>> + > >>> static const struct file_operations sel_avc_cache_threshold_ops = { > >>> .read = sel_read_avc_cache_threshold, > >>> .write = sel_write_avc_cache_threshold, > >>> @@ -1572,6 +1598,7 @@ static int sel_make_avc_files(struct dentry *dir) > >>> { "cache_threshold", > >>> &sel_avc_cache_threshold_ops, S_IRUGO|S_IWUSR }, > >>> { "hash_stats", &sel_avc_hash_stats_ops, S_IRUGO }, > >>> + { "sidtab_hash_stats", &sel_sidtab_hash_stats_ops, S_IRUGO }, > >>> #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS > >>> { "cache_stats", &sel_avc_cache_stats_ops, S_IRUGO }, > >>> #endif > >>> diff --git a/security/selinux/ss/context.h b/security/selinux/ss/context.h > >>> index 513e67f48878..01fea944177d 100644 > >>> --- a/security/selinux/ss/context.h > >>> +++ b/security/selinux/ss/context.h > >>> @@ -31,6 +31,7 @@ struct context { > >>> u32 len; /* length of string in bytes */ > >>> struct mls_range range; > >>> char *str; /* string representation if context cannot be mapped. */ > >>> + u32 hash; /* a hash of the string representation */ > >>> }; > >>> > >>> static inline void mls_context_init(struct context *c) > >>> @@ -168,6 +169,7 @@ static inline int context_cpy(struct context *dst, struct context *src) > >>> kfree(dst->str); > >>> return rc; > >>> } > >>> + dst->hash = src->hash; > >>> return 0; > >>> } > >>> > >>> @@ -182,6 +184,8 @@ static inline void context_destroy(struct context *c) > >>> > >>> static inline int context_cmp(struct context *c1, struct context *c2) > >>> { > >>> + if (c1->hash && c2->hash && (c1->hash != c2->hash)) > >>> + return 0; > >>> if (c1->len && c2->len) > >>> return (c1->len == c2->len && !strcmp(c1->str, c2->str)); > >>> if (c1->len || c2->len) > >>> @@ -192,5 +196,10 @@ static inline int context_cmp(struct context *c1, struct context *c2) > >>> mls_context_cmp(c1, c2)); > >>> } > >>> > >>> +static inline unsigned int context_compute_hash(const char *s) > >>> +{ > >>> + return full_name_hash(NULL, s, strlen(s)); > >>> +} > >>> + > >>> #endif /* _SS_CONTEXT_H_ */ > >>> > >>> diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c > >>> index e20624a68f5d..e369b0092cdf 100644 > >>> --- a/security/selinux/ss/policydb.c > >>> +++ b/security/selinux/ss/policydb.c > >>> @@ -878,6 +878,11 @@ int policydb_load_isids(struct policydb *p, struct sidtab *s) > >>> sidtab_destroy(s); > >>> goto out; > >>> } > >>> + rc = context_add_hash(p, &c->context[0]); > >>> + if (rc) { > >>> + sidtab_destroy(s); > >>> + goto out; > >>> + } > >>> > >>> rc = sidtab_set_initial(s, c->sid[0], &c->context[0]); > >>> if (rc) { > >>> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c > >>> index a5813c7629c1..29076c15cdf7 100644 > >>> --- a/security/selinux/ss/services.c > >>> +++ b/security/selinux/ss/services.c > >>> @@ -1257,6 +1257,11 @@ static int context_struct_to_string(struct policydb *p, > >>> > >>> #include "initial_sid_to_string.h" > >>> > >>> +int security_sidtab_hash_stats(struct selinux_state *state, char *page) > >>> +{ > >>> + return sidtab_hash_stats(state->ss->sidtab, page); > >>> +} > >>> + > >>> const char *security_get_initial_sid_context(u32 sid) > >>> { > >>> if (unlikely(sid > SECINITSID_NUM)) > >>> @@ -1384,6 +1389,8 @@ static int string_to_context_struct(struct policydb *pol, > >>> int rc = 0; > >>> > >>> context_init(ctx); > >>> + /* hash the string before it gets mutated */ > >>> + ctx->hash = context_compute_hash(scontext); > >>> > >>> /* Parse the security context. */ > >>> > >>> @@ -1442,6 +1449,7 @@ static int string_to_context_struct(struct policydb *pol, > >>> rc = -EINVAL; > >>> if (!policydb_context_isvalid(pol, ctx)) > >>> goto out; > >>> + > >>> rc = 0; > >>> out: > >>> if (rc) > >>> @@ -1449,6 +1457,42 @@ static int string_to_context_struct(struct policydb *pol, > >>> return rc; > >>> } > >>> > >>> +int context_add_hash(struct policydb *policydb, > >>> + struct context *context) > >>> +{ > >>> + int rc; > >>> + char *str; > >>> + int len; > >>> + > >>> + if (context->str) { > >>> + context->hash = context_compute_hash(context->str); > >>> + } else { > >>> + rc = context_struct_to_string(policydb, context, > >>> + &str, &len); > >>> + if (rc) > >>> + return rc; > >>> + context->hash = context_compute_hash(str); > >>> + kfree(str); > >>> + } > >>> + return 0; > >>> +} > >>> + > >>> +static int context_to_sid(struct selinux_state *state, > >>> + struct context *context, u32 *sid) > >>> +{ > >>> + int rc; > >>> + struct sidtab *sidtab = state->ss->sidtab; > >>> + struct policydb *policydb = &state->ss->policydb; > >>> + > >>> + if (!context->hash) { > >>> + rc = context_add_hash(policydb, context); > >>> + if (rc) > >>> + return rc; > >>> + } > >>> + > >>> + return sidtab_context_to_sid(sidtab, context, sid); > >>> +} > >>> + > >>> static int security_context_to_sid_core(struct selinux_state *state, > >>> const char *scontext, u32 scontext_len, > >>> u32 *sid, u32 def_sid, gfp_t gfp_flags, > >>> @@ -1501,7 +1545,7 @@ static int security_context_to_sid_core(struct selinux_state *state, > >>> str = NULL; > >>> } else if (rc) > >>> goto out_unlock; > >>> - rc = sidtab_context_to_sid(sidtab, &context, sid); > >>> + rc = context_to_sid(state, &context, sid); > >>> context_destroy(&context); > >>> out_unlock: > >>> read_unlock(&state->ss->policy_rwlock); > >>> @@ -1805,7 +1849,7 @@ static int security_compute_sid(struct selinux_state *state, > >>> goto out_unlock; > >>> } > >>> /* Obtain the sid for the context. */ > >>> - rc = sidtab_context_to_sid(sidtab, &newcontext, out_sid); > >>> + rc = context_to_sid(state, &newcontext, out_sid); > >>> out_unlock: > >>> read_unlock(&state->ss->policy_rwlock); > >>> context_destroy(&newcontext); > >>> @@ -2033,6 +2077,10 @@ static int convert_context(struct context *oldc, struct context *newc, void *p) > >>> goto bad; > >>> } > >>> > >>> + rc = context_add_hash(args->newp, newc); > >>> + if (rc) > >>> + goto bad; > >>> + > >>> return 0; > >>> bad: > >>> /* Map old representation to string and save it. */ > >>> @@ -2280,9 +2328,7 @@ int security_port_sid(struct selinux_state *state, > >>> > >>> if (c) { > >>> if (!c->sid[0]) { > >>> - rc = sidtab_context_to_sid(sidtab, > >>> - &c->context[0], > >>> - &c->sid[0]); > >>> + rc = context_to_sid(state, &c->context[0], &c->sid[0]); > >>> if (rc) > >>> goto out; > >>> } > >>> @@ -2374,9 +2420,7 @@ int security_ib_endport_sid(struct selinux_state *state, > >>> > >>> if (c) { > >>> if (!c->sid[0]) { > >>> - rc = sidtab_context_to_sid(sidtab, > >>> - &c->context[0], > >>> - &c->sid[0]); > >>> + rc = context_to_sid(state, &c->context[0], &c->sid[0]); > >>> if (rc) > >>> goto out; > >>> } > >>> @@ -2416,14 +2460,10 @@ int security_netif_sid(struct selinux_state *state, > >>> > >>> if (c) { > >>> if (!c->sid[0] || !c->sid[1]) { > >>> - rc = sidtab_context_to_sid(sidtab, > >>> - &c->context[0], > >>> - &c->sid[0]); > >>> + rc = context_to_sid(state, &c->context[0], &c->sid[0]); > >>> if (rc) > >>> goto out; > >>> - rc = sidtab_context_to_sid(sidtab, > >>> - &c->context[1], > >>> - &c->sid[1]); > >>> + rc = context_to_sid(state, &c->context[1], &c->sid[1]); > >>> if (rc) > >>> goto out; > >>> } > >>> @@ -2601,7 +2641,7 @@ int security_get_user_sids(struct selinux_state *state, > >>> &usercon)) > >>> continue; > >>> > >>> - rc = sidtab_context_to_sid(sidtab, &usercon, &sid); > >>> + rc = context_to_sid(state, &usercon, &sid); > >>> if (rc) > >>> goto out_unlock; > >>> if (mynel < maxnel) { > >>> @@ -2672,7 +2712,6 @@ static inline int __security_genfs_sid(struct selinux_state *state, > >>> u32 *sid) > >>> { > >>> struct policydb *policydb = &state->ss->policydb; > >>> - struct sidtab *sidtab = state->ss->sidtab; > >>> int len; > >>> u16 sclass; > >>> struct genfs *genfs; > >>> @@ -2707,7 +2746,7 @@ static inline int __security_genfs_sid(struct selinux_state *state, > >>> goto out; > >>> > >>> if (!c->sid[0]) { > >>> - rc = sidtab_context_to_sid(sidtab, &c->context[0], &c->sid[0]); > >>> + rc = context_to_sid(state, &c->context[0], &c->sid[0]); > >>> if (rc) > >>> goto out; > >>> } > >>> @@ -2770,8 +2809,7 @@ int security_fs_use(struct selinux_state *state, struct super_block *sb) > >>> if (c) { > >>> sbsec->behavior = c->v.behavior; > >>> if (!c->sid[0]) { > >>> - rc = sidtab_context_to_sid(sidtab, &c->context[0], > >>> - &c->sid[0]); > >>> + rc = context_to_sid(state, &c->context[0], &c->sid[0]); > >>> if (rc) > >>> goto out; > >>> } > >>> @@ -3026,8 +3064,7 @@ int security_sid_mls_copy(struct selinux_state *state, > >>> goto out_unlock; > >>> } > >>> } > >>> - > >>> - rc = sidtab_context_to_sid(sidtab, &newcon, new_sid); > >>> + rc = context_to_sid(state, &newcon, new_sid); > >>> out_unlock: > >>> read_unlock(&state->ss->policy_rwlock); > >>> context_destroy(&newcon); > >>> @@ -3620,7 +3657,7 @@ int security_netlbl_secattr_to_sid(struct selinux_state *state, > >>> if (!mls_context_isvalid(policydb, &ctx_new)) > >>> goto out_free; > >>> > >>> - rc = sidtab_context_to_sid(sidtab, &ctx_new, sid); > >>> + rc = context_to_sid(state, &ctx_new, sid); > >>> if (rc) > >>> goto out_free; > >>> > >>> diff --git a/security/selinux/ss/services.h b/security/selinux/ss/services.h > >>> index 9a36de860368..fc40640a9725 100644 > >>> --- a/security/selinux/ss/services.h > >>> +++ b/security/selinux/ss/services.h > >>> @@ -8,7 +8,7 @@ > >>> #define _SS_SERVICES_H_ > >>> > >>> #include "policydb.h" > >>> -#include "sidtab.h" > >>> +#include "context.h" > >>> > >>> /* Mapping for a single class */ > >>> struct selinux_mapping { > >>> @@ -39,4 +39,6 @@ void services_compute_xperms_drivers(struct extended_perms *xperms, > >>> void services_compute_xperms_decision(struct extended_perms_decision *xpermd, > >>> struct avtab_node *node); > >>> > >>> +int context_add_hash(struct policydb *policydb, struct context *context); > >>> + > >>> #endif /* _SS_SERVICES_H_ */ > >>> diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c > >>> index 7d49994e8d5f..e4710f32b6d9 100644 > >>> --- a/security/selinux/ss/sidtab.c > >>> +++ b/security/selinux/ss/sidtab.c > >>> @@ -23,23 +23,32 @@ int sidtab_init(struct sidtab *s) > >>> > >>> memset(s->roots, 0, sizeof(s->roots)); > >>> > >>> - /* max count is SIDTAB_MAX so valid index is always < SIDTAB_MAX */ > >>> - for (i = 0; i < SIDTAB_RCACHE_SIZE; i++) > >>> - s->rcache[i] = SIDTAB_MAX; > >>> - > >>> for (i = 0; i < SECINITSID_NUM; i++) > >>> s->isids[i].set = 0; > >>> > >>> s->count = 0; > >>> s->convert = NULL; > >>> + hash_init(s->context_to_sid); > >>> > >>> spin_lock_init(&s->lock); > >>> return 0; > >>> } > >>> > >>> +static u32 context_to_sid(struct sidtab *s, struct context *context) > >>> +{ > >>> + struct sidtab_node *node; > >>> + > >>> + hash_for_each_possible(s->context_to_sid, node, list, context->hash) { > >> > >> Is this safe without any locking or any kind of memory barrier pair to > >> deal with hash_add() calls? > > > > My understanding is that it is because hlist_add_head is written to be > > safe for this type of lockless access. > > > > It performs all modifications on the new node first and only then uses > > WRITE_ONCE() to write the list head's ->next pointer atomically and prevent > > reordering. > > > > (similar explanation here: https://lore.kernel.org/patchwork/patch/624316/) > > > > "Code that does lockless emptiness testing of non-RCU lists is relying > > on INIT_LIST_HEAD() to write the list head's ->next pointer atomically, > > particularly when INIT_LIST_HEAD() is invoked from list_del_init(). > > This commit therefore adds WRITE_ONCE() to this function's pointer stores > > that could affect the head's ->next pointer." > > Wondering if we still need at least a write barrier in the code that > adds a node prior to hash_add() to ensure the node contents are sane. I'm not sure what you mean. Are you concerned about compiler reordering? > > > > > > > > >> > >>> + if (context_cmp(node->context, context)) > >>> + return node->sid; > >>> + } > >>> + return 0; > >>> +} > >>> + > >>> int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context) > >>> { > >>> struct sidtab_isid_entry *entry; > >>> + struct sidtab_node *node = NULL; > >>> int rc; > >>> > >>> if (sid == 0 || sid > SECINITSID_NUM) > >>> @@ -52,9 +61,57 @@ int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context) > >>> return rc; > >>> > >>> entry->set = 1; > >>> + > >>> + /* > >>> + * Multiple initial sids may map to the same context. Check that this > >>> + * context is not already represented in the context_to_sid hashtable > >>> + * to avoid duplicate entries and long linked lists upon hash > >>> + * collision. > >>> + */ > >>> + if (!context_to_sid(s, context)) { > >>> + node = kzalloc(sizeof(struct sidtab_node), GFP_ATOMIC); > >>> + if (!node) > >>> + return -ENOMEM; > >>> + node->sid = sid; > >>> + node->context = &entry->context; > >>> + hash_add(s->context_to_sid, &node->list, context->hash); > >>> + } > >>> + > >>> return 0; > >>> } > >>> > >>> +int sidtab_hash_stats(struct sidtab *sidtab, char *page) > >>> +{ > >>> + int i; > >>> + int chain_len = 0; > >>> + int slots_used = 0; > >>> + int entries = 0; > >>> + int max_chain_len = 0; > >>> + int cur_bucket = 0; > >>> + struct sidtab_node *node; > >>> + > >>> + > >>> + hash_for_each(sidtab->context_to_sid, i, node, list) { > >>> + entries++; > >>> + if (i == cur_bucket) { > >>> + chain_len++; > >>> + if (chain_len == 1) > >>> + slots_used++; > >>> + } else { > >>> + cur_bucket = i; > >>> + if (chain_len > max_chain_len) > >>> + max_chain_len = chain_len; > >>> + chain_len = 0; > >>> + } > >>> + } > >>> + if (chain_len > max_chain_len) > >>> + max_chain_len = chain_len; > >>> + return scnprintf(page, PAGE_SIZE, "%s: %d entries and %d/%d buckets " > >>> + "used, longest chain length %d\n", "context_to_sid", > >>> + entries, slots_used, SIDTAB_HASH_BUCKETS, > >>> + max_chain_len); > >>> +} > >>> + > >>> static u32 sidtab_level_from_count(u32 count) > >>> { > >>> u32 capacity = SIDTAB_LEAF_ENTRIES; > >>> @@ -150,7 +207,7 @@ static struct context *sidtab_search_core(struct sidtab *s, u32 sid, int force) > >>> > >>> if (sid != 0) { > >>> if (sid > SECINITSID_NUM) > >>> - context = sidtab_lookup(s, sid - (SECINITSID_NUM + 1)); > >>> + context = sidtab_lookup(s, sid_to_index(sid)); > >>> else > >>> context = sidtab_lookup_initial(s, sid); > >>> if (context && (!context->len || force)) > >>> @@ -170,132 +227,70 @@ 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) { > >>> - WRITE_ONCE(s->rcache[pos], READ_ONCE(s->rcache[pos - 1])); > >>> - --pos; > >>> - } > >>> - WRITE_ONCE(s->rcache[0], 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++) { > >>> - u32 v = READ_ONCE(s->rcache[i]); > >>> - > >>> - if (v >= SIDTAB_MAX) > >>> - continue; > >>> - > >>> - if (context_cmp(sidtab_do_lookup(s, v, 0), context)) { > >>> - sidtab_rcache_update(s, v, i); > >>> - *index = v; > >>> - return 0; > >>> - } > >>> - } > >>> - return -ENOENT; > >>> -} > >>> - > >>> -static int sidtab_reverse_lookup(struct sidtab *s, struct context *context, > >>> - u32 *index) > >>> +int sidtab_context_to_sid(struct sidtab *s, struct context *context, > >>> + u32 *sid) > >>> { > >>> unsigned long flags; > >>> - u32 count, count_locked, level, pos; > >>> + u32 count; > >>> struct sidtab_convert_params *convert; > >>> struct context *dst, *dst_convert; > >>> + struct sidtab_node *dst_node, *dst_node_convert = NULL; > >>> int rc; > >>> > >>> - rc = sidtab_rcache_search(s, context, index); > >>> - if (rc == 0) > >>> - return 0; > >>> - > >>> - /* read entries only after reading count */ > >>> - count = smp_load_acquire(&s->count); > >>> - level = sidtab_level_from_count(count); > >>> - > >>> - pos = 0; > >>> - rc = sidtab_find_context(s->roots[level], &pos, count, level, > >>> - context, index); > >>> - if (rc == 0) { > >>> - sidtab_rcache_push(s, *index); > >>> + *sid = context_to_sid(s, context); > >>> + if (*sid) > >>> return 0; > >>> - } > >>> > >>> /* lock-free search failed: lock, re-search, and insert if not found */ > >>> spin_lock_irqsave(&s->lock, flags); > >>> > >>> + *sid = context_to_sid(s, context); > >>> + if (*sid) > >>> + goto out_unlock; > >>> + > >>> convert = s->convert; > >>> - count_locked = 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; > >>> + count = s->count; > >>> + > >>> + rc = -ENOMEM; > >>> + dst_node = kzalloc(sizeof(struct sidtab_node), GFP_ATOMIC); > >>> + if (!dst_node) > >>> + goto out_unlock; > >>> + > >>> + if (convert) { > >>> + dst_node_convert = kzalloc(sizeof(struct sidtab_node), > >>> + GFP_ATOMIC); > >>> + if (!dst_node_convert) { > >>> + kfree(dst_node); > >>> goto out_unlock; > >>> } > >>> - ++count; > >>> } > >>> > >>> /* bail out if we already reached max entries */ > >>> rc = -EOVERFLOW; > >>> - if (count >= SIDTAB_MAX) > >>> + if (count >= SIDTAB_MAX) { > >>> + kfree(dst_node); > >>> + kfree(dst_node_convert); > >>> goto out_unlock; > >>> + } > >>> > >>> /* insert context into new entry */ > >>> rc = -ENOMEM; > >>> dst = sidtab_do_lookup(s, count, 1); > >>> - if (!dst) > >>> + if (!dst) { > >>> + kfree(dst_node); > >>> + kfree(dst_node_convert); > >>> goto out_unlock; > >>> + } > >>> + > >>> + dst_node->sid = index_to_sid(count); > >>> + dst_node->context = dst; > >>> > >>> rc = context_cpy(dst, context); > >>> - if (rc) > >>> + if (rc) { > >>> + kfree(dst_node); > >>> + kfree(dst_node_convert); > >>> goto out_unlock; > >>> + } > >>> > >>> /* > >>> * if we are building a new sidtab, we need to convert the context > >>> @@ -306,25 +301,35 @@ static int sidtab_reverse_lookup(struct sidtab *s, struct context *context, > >>> dst_convert = sidtab_do_lookup(convert->target, count, 1); > >>> if (!dst_convert) { > >>> context_destroy(dst); > >>> + kfree(dst_node); > >>> + kfree(dst_node_convert); > >>> goto out_unlock; > >>> } > >>> > >>> rc = convert->func(context, dst_convert, convert->args); > >>> if (rc) { > >>> context_destroy(dst); > >>> + kfree(dst_node); > >>> + kfree(dst_node_convert); > >>> goto out_unlock; > >>> } > >>> + dst_node_convert->sid = index_to_sid(count); > >>> + dst_node_convert->context = dst_convert; > >>> > >>> /* at this point we know the insert won't fail */ > >>> + spin_lock_irqsave(&convert->target->lock, flags); > >>> convert->target->count = count + 1; > >>> + hash_add(convert->target->context_to_sid, > >>> + &dst_node_convert->list, dst_convert->hash); > >>> + spin_unlock_irqrestore(&convert->target->lock, flags); > >>> } > >>> + hash_add(s->context_to_sid, &dst_node->list, context->hash); > >>> > >>> if (context->len) > >>> pr_info("SELinux: Context %s is not valid (left unmapped).\n", > >>> context->str); > >>> > >>> - sidtab_rcache_push(s, count); > >>> - *index = count; > >>> + *sid = index_to_sid(count); > >>> > >>> /* write entries before writing new count */ > >>> smp_store_release(&s->count, count + 1); > >>> @@ -335,27 +340,41 @@ static int sidtab_reverse_lookup(struct sidtab *s, struct context *context, > >>> return rc; > >>> } > >>> > >>> -int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid) > >>> +static int sidtab_convert_hashnode(struct sidtab *s, u32 index) > >>> { > >>> - int rc; > >>> - u32 i; > >>> + unsigned long flags; > >>> + struct context *context; > >>> + struct sidtab_node *node; > >>> > >>> - for (i = 0; i < SECINITSID_NUM; i++) { > >>> - struct sidtab_isid_entry *entry = &s->isids[i]; > >>> + context = sidtab_do_lookup(s, index, 0); > >>> > >>> - if (entry->set && context_cmp(context, &entry->context)) { > >>> - *sid = i + 1; > >>> - return 0; > >>> - } > >>> - } > >>> + node = kzalloc(sizeof(struct sidtab_node), GFP_ATOMIC); > >>> + if (!node) > >>> + return -ENOMEM; > >>> > >>> - rc = sidtab_reverse_lookup(s, context, sid); > >>> - if (rc) > >>> - return rc; > >>> - *sid += SECINITSID_NUM + 1; > >>> + node->sid = index_to_sid(index); > >>> + node->context = context; > >>> + spin_lock_irqsave(&s->lock, flags); > >>> + hash_add(s->context_to_sid, &node->list, context->hash); > >>> + spin_unlock_irqrestore(&s->lock, flags); > >>> return 0; > >>> } > >>> > >>> +static int sidtab_convert_hashtable(struct sidtab *s, u32 count) > >>> +{ > >>> + u32 i; > >>> + int rc = 0; > >>> + > >>> + for (i = 0; i < count; i++) { > >>> + rc = sidtab_convert_hashnode(s, i); > >>> + if (rc) > >>> + break; > >>> + > >>> + cond_resched(); > >>> + } > >>> + return rc; > >>> +} > >>> + > >>> static int sidtab_convert_tree(union sidtab_entry_inner *edst, > >>> union sidtab_entry_inner *esrc, > >>> u32 *pos, u32 count, u32 level, > >>> @@ -400,6 +419,7 @@ static int sidtab_convert_tree(union sidtab_entry_inner *edst, > >>> } > >>> cond_resched(); > >>> } > >>> + > >>> return 0; > >>> } > >>> > >>> @@ -449,7 +469,16 @@ int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params) > >>> spin_lock_irqsave(&s->lock, flags); > >>> s->convert = NULL; > >>> spin_unlock_irqrestore(&s->lock, flags); > >>> + return rc; > >>> + } > >>> + > >>> + rc = sidtab_convert_hashtable(params->target, count); > >>> + if (rc) { > >>> + spin_lock_irqsave(&s->lock, flags); > >>> + s->convert = NULL; > >>> + spin_unlock_irqrestore(&s->lock, flags); > >>> } > >>> + > >>> return rc; > >>> } > >>> > >>> @@ -478,6 +507,19 @@ static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level) > >>> } > >>> } > >>> > >>> + > >>> +static void sidtab_destroy_hashtable(struct sidtab *s) > >>> +{ > >>> + struct sidtab_node *node; > >>> + struct hlist_node *tmp; > >>> + int i; > >>> + > >>> + hash_for_each_safe(s->context_to_sid, i, tmp, node, list) { > >>> + hash_del(&node->list); > >>> + kfree(node); > >>> + } > >>> +} > >>> + > >>> void sidtab_destroy(struct sidtab *s) > >>> { > >>> u32 i, level; > >>> @@ -491,4 +533,5 @@ void sidtab_destroy(struct sidtab *s) > >>> --level; > >>> > >>> sidtab_destroy_tree(s->roots[level], level); > >>> + sidtab_destroy_hashtable(s); > >>> } > >>> diff --git a/security/selinux/ss/sidtab.h b/security/selinux/ss/sidtab.h > >>> index 1f4763141aa1..85afef719a43 100644 > >>> --- a/security/selinux/ss/sidtab.h > >>> +++ b/security/selinux/ss/sidtab.h > >>> @@ -13,6 +13,7 @@ > >>> > >>> #include <linux/spinlock_types.h> > >>> #include <linux/log2.h> > >>> +#include <linux/hashtable.h> > >>> > >>> #include "context.h" > >>> > >>> @@ -66,7 +67,16 @@ struct sidtab_convert_params { > >>> struct sidtab *target; > >>> }; > >>> > >>> -#define SIDTAB_RCACHE_SIZE 3 > >>> +struct sidtab_node { > >>> + u32 sid; > >>> + struct context *context; > >>> + struct hlist_node list; > >>> +}; > >>> + > >>> +#define SIDTAB_HASH_BITS 9 > >>> +#define SIDTAB_HASH_BUCKETS (1 << SIDTAB_HASH_BITS) > >>> +#define index_to_sid(index) (index + SECINITSID_NUM + 1) > >>> +#define sid_to_index(sid) (sid - (SECINITSID_NUM + 1)) > >>> > >>> struct sidtab { > >>> /* > >>> @@ -83,11 +93,11 @@ struct sidtab { > >>> struct sidtab_convert_params *convert; > >>> spinlock_t lock; > >>> > >>> - /* reverse lookup cache - access atomically via {READ|WRITE}_ONCE() */ > >>> - u32 rcache[SIDTAB_RCACHE_SIZE]; > >>> - > >>> /* index == SID - 1 (no entry for SECSID_NULL) */ > >>> struct sidtab_isid_entry isids[SECINITSID_NUM]; > >>> + > >>> + /* Hash table for fast reverse context-to-sid lookups. */ > >>> + DECLARE_HASHTABLE(context_to_sid, SIDTAB_HASH_BITS); > >>> }; > >>> > >>> int sidtab_init(struct sidtab *s); > >>> @@ -101,6 +111,8 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid); > >>> > >>> void sidtab_destroy(struct sidtab *s); > >>> > >>> +int sidtab_hash_stats(struct sidtab *sidtab, char *page); > >>> + > >>> #endif /* _SS_SIDTAB_H_ */ > >>> > >>> > >>> > >> >
