From: Jeffrey Vander Stoep <jeffv@google.com>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: SElinux list <selinux@vger.kernel.org>,
Jovana Knezevic <jovanak@google.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
Paul Moore <paul@paul-moore.com>
Subject: Re: [PATCH] selinux: sidtab: reverse lookup hash table
Date: Wed, 30 Oct 2019 20:07:34 +0100 [thread overview]
Message-ID: <CABXk95CLsQx9gaQn+QxpuU5aj4mVCK5V9Y1ZeYhhsYk_-c5q_g@mail.gmail.com> (raw)
In-Reply-To: <7cc2b7c7-9f79-96e3-eccf-6661e7a51291@tycho.nsa.gov>
On Wed, Oct 30, 2019 at 7:57 PM Stephen Smalley <sds@tycho.nsa.gov> wrote:
>
> On 10/30/19 2:33 PM, Jeffrey Vander Stoep wrote:
> > On Wed, Oct 30, 2019 at 7:06 PM Stephen Smalley <sds@tycho.nsa.gov> 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@google.com>
> >>> Reported-by: Stephen Smalley <sds@tycho.nsa.gov>
> >>> Reported-by: Jovana Knezevic <jovanak@google.com>
> >>> ---
> >>> 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_ */
> >>>
> >>>
> >>>
> >>
>
next prev parent reply other threads:[~2019-10-30 19:07 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-30 10:19 [PATCH] selinux: sidtab: reverse lookup hash table Jeff Vander Stoep
2019-10-30 12:37 ` Ondrej Mosnacek
2019-10-30 13:21 ` Jeffrey Vander Stoep
2019-10-30 15:24 ` Stephen Smalley
2019-10-30 16:32 ` Stephen Smalley
2019-10-30 16:36 ` Stephen Smalley
2019-10-30 17:14 ` Stephen Smalley
2019-10-30 18:06 ` Stephen Smalley
2019-10-30 18:33 ` Jeffrey Vander Stoep
2019-10-30 18:57 ` Stephen Smalley
2019-10-30 19:07 ` Jeffrey Vander Stoep [this message]
2019-10-30 20:02 ` Stephen Smalley
2019-10-30 20:06 ` Jeffrey Vander Stoep
2019-10-30 20:48 ` Paul Moore
2019-11-02 19:52 ` Ondrej Mosnacek
2019-11-07 20:52 Jeff Vander Stoep
2019-11-15 0:04 ` Paul Moore
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