SELinux: improve performance when AVC misses.

* We add ebitmap_for_each_positive_bit() which enables to walk on
  any positive bit on the given ebitmap, to improve its performance
  using common bit-operations defined in linux/bitops.h.
  In the previous version, this logic was implemented using a combination
  of ebitmap_for_each_bit() and ebitmap_node_get_bit(), but is was worse
  in performance aspect.
  This logic is most frequestly used to compute a new AVC entry,
  so this patch can improve SELinux performance when AVC misses are happen.
* struct ebitmap_node is redefined as an array of "unsigned long", to get
  suitable for using find_next_bit() which is fasted than iteration of
  shift and logical operation, and to maximize memory usage allocated
  from general purpose slab.
* Any ebitmap_for_each_bit() are repleced by the new implementation
  in ss/service.c and ss/mls.c. Some of related implementation are
  changed, however, there is no incompatibility with the previous
  version.
* The width of any new line are less or equal than 80-chars.

The following benchmark shows the effect of this patch, when we
access many files which have different security context one after
another. The number is more than /selinux/avc/cache_threshold, so
any access always causes AVC misses.

      selinux-2.6      selinux-2.6-ebitmap
AVG:   22.763 [s]          8.750 [s]
STD:    0.265              0.019
------------------------------------------
1st:   22.558 [s]          8.786 [s]
2nd:   22.458 [s]          8.750 [s]
3rd:   22.478 [s]          8.754 [s]
4th:   22.724 [s]          8.745 [s]
5th:   22.918 [s]          8.748 [s]
6th:   22.905 [s]          8.764 [s]
7th:   23.238 [s]          8.726 [s]
8th:   22.822 [s]          8.729 [s]

Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

4 files changed, 303 insertions, 237 deletions

diff --git a/security/selinux/ss/ebitmap.c b/security/selinux/ss/ebitmap.c
index ce492a6b38e..ae44c0c9401 100644
--- a/security/selinux/ss/ebitmap.c
+++ b/security/selinux/ss/ebitmap.c
@@ -10,6 +10,10 @@
  *
  * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
  */
+/*
+ * Updated: KaiGai Kohei <kaigai@ak.jp.nec.com>
+ *      Applied standard bit operations to improve bitmap scanning.
+ */
 
 #include <linux/kernel.h>
 #include <linux/slab.h>
@@ -29,7 +33,7 @@ int ebitmap_cmp(struct ebitmap *e1, struct ebitmap *e2)
         n2 = e2->node;
         while (n1 && n2 &&
                (n1->startbit == n2->startbit) &&
-               (n1->map == n2->map)) {
+               !memcmp(n1->maps, n2->maps, EBITMAP_SIZE / 8)) {
                 n1 = n1->next;
                 n2 = n2->next;
         }
@@ -54,7 +58,7 @@ int ebitmap_cpy(struct ebitmap *dst, struct ebitmap *src)
                         return -ENOMEM;
                 }
                 new->startbit = n->startbit;
-                new->map = n->map;
+                memcpy(new->maps, n->maps, EBITMAP_SIZE / 8);
                 new->next = NULL;
                 if (prev)
                         prev->next = new;
@@ -84,13 +88,15 @@ int ebitmap_netlbl_export(struct ebitmap *ebmap,
 {
         struct ebitmap_node *e_iter = ebmap->node;
         struct netlbl_lsm_secattr_catmap *c_iter;
-        u32 cmap_idx;
+        u32 cmap_idx, cmap_sft;
+        int i;
 
-        /* This function is a much simpler because SELinux's MAPTYPE happens
-         * to be the same as NetLabel's NETLBL_CATMAP_MAPTYPE, if MAPTYPE is
-         * changed from a u64 this function will most likely need to be changed
-         * as well.  It's not ideal but I think the tradeoff in terms of
-         * neatness and speed is worth it. */
+        /* NetLabel's NETLBL_CATMAP_MAPTYPE is defined as an array of u64,
+         * however, it is not always compatible with an array of unsigned long
+         * in ebitmap_node.
+         * In addition, you should pay attention the following implementation
+         * assumes unsigned long has a width equal with or less than 64-bit.
+         */
 
         if (e_iter == NULL) {
                 *catmap = NULL;
@@ -104,19 +110,27 @@ int ebitmap_netlbl_export(struct ebitmap *ebmap,
         c_iter->startbit = e_iter->startbit & ~(NETLBL_CATMAP_SIZE - 1);
 
         while (e_iter != NULL) {
-                if (e_iter->startbit >=
-                    (c_iter->startbit + NETLBL_CATMAP_SIZE)) {
-                        c_iter->next = netlbl_secattr_catmap_alloc(GFP_ATOMIC);
-                        if (c_iter->next == NULL)
-                                goto netlbl_export_failure;
-                        c_iter = c_iter->next;
-                        c_iter->startbit = e_iter->startbit &
-                                           ~(NETLBL_CATMAP_SIZE - 1);
+                for (i = 0; i < EBITMAP_UNIT_NUMS; i++) {
+                        unsigned int delta, e_startbit, c_endbit;
+
+                        e_startbit = e_iter->startbit + i * EBITMAP_UNIT_SIZE;
+                        c_endbit = c_iter->startbit + NETLBL_CATMAP_SIZE;
+                        if (e_startbit >= c_endbit) {
+                                c_iter->next
+                                  = netlbl_secattr_catmap_alloc(GFP_ATOMIC);
+                                if (c_iter->next == NULL)
+                                        goto netlbl_export_failure;
+                                c_iter = c_iter->next;
+                                c_iter->startbit
+                                  = e_startbit & ~(NETLBL_CATMAP_SIZE - 1);
+                        }
+                        delta = e_startbit - c_iter->startbit;
+                        cmap_idx = delta / NETLBL_CATMAP_MAPSIZE;
+                        cmap_sft = delta % NETLBL_CATMAP_MAPSIZE;
+                        c_iter->bitmap[cmap_idx]
+                                |= e_iter->maps[cmap_idx] << cmap_sft;
+                        e_iter = e_iter->next;
                 }
-                cmap_idx = (e_iter->startbit - c_iter->startbit) /
-                           NETLBL_CATMAP_MAPSIZE;
-                c_iter->bitmap[cmap_idx] = e_iter->map;
-                e_iter = e_iter->next;
         }
 
         return 0;
@@ -128,7 +142,7 @@ netlbl_export_failure:
 
 /**
  * ebitmap_netlbl_import - Import a NetLabel category bitmap into an ebitmap
- * @ebmap: the ebitmap to export
+ * @ebmap: the ebitmap to import
  * @catmap: the NetLabel category bitmap
  *
  * Description:
@@ -142,36 +156,50 @@ int ebitmap_netlbl_import(struct ebitmap *ebmap,
         struct ebitmap_node *e_iter = NULL;
         struct ebitmap_node *emap_prev = NULL;
         struct netlbl_lsm_secattr_catmap *c_iter = catmap;
-        u32 c_idx;
+        u32 c_idx, c_pos, e_idx, e_sft;
 
-        /* This function is a much simpler because SELinux's MAPTYPE happens
-         * to be the same as NetLabel's NETLBL_CATMAP_MAPTYPE, if MAPTYPE is
-         * changed from a u64 this function will most likely need to be changed
-         * as well.  It's not ideal but I think the tradeoff in terms of
-         * neatness and speed is worth it. */
+        /* NetLabel's NETLBL_CATMAP_MAPTYPE is defined as an array of u64,
+         * however, it is not always compatible with an array of unsigned long
+         * in ebitmap_node.
+         * In addition, you should pay attention the following implementation
+         * assumes unsigned long has a width equal with or less than 64-bit.
+         */
 
         do {
                 for (c_idx = 0; c_idx < NETLBL_CATMAP_MAPCNT; c_idx++) {
-                        if (c_iter->bitmap[c_idx] == 0)
+                        unsigned int delta;
+                        u64 map = c_iter->bitmap[c_idx];
+
+                        if (!map)
                                 continue;
 
-                        e_iter = kzalloc(sizeof(*e_iter), GFP_ATOMIC);
-                        if (e_iter == NULL)
-                                goto netlbl_import_failure;
-                        if (emap_prev == NULL)
-                                ebmap->node = e_iter;
-                        else
-                                emap_prev->next = e_iter;
-                        emap_prev = e_iter;
-
-                        e_iter->startbit = c_iter->startbit +
-                                           NETLBL_CATMAP_MAPSIZE * c_idx;
-                        e_iter->map = c_iter->bitmap[c_idx];
+                        c_pos = c_iter->startbit
+                                + c_idx * NETLBL_CATMAP_MAPSIZE;
+                        if (!e_iter
+                            || c_pos >= e_iter->startbit + EBITMAP_SIZE) {
+                                e_iter = kzalloc(sizeof(*e_iter), GFP_ATOMIC);
+                                if (!e_iter)
+                                        goto netlbl_import_failure;
+                                e_iter->startbit
+                                        = c_pos - (c_pos % EBITMAP_SIZE);
+                                if (emap_prev == NULL)
+                                        ebmap->node = e_iter;
+                                else
+                                        emap_prev->next = e_iter;
+                                emap_prev = e_iter;
+                        }
+                        delta = c_pos - e_iter->startbit;
+                        e_idx = delta / EBITMAP_UNIT_SIZE;
+                        e_sft = delta % EBITMAP_UNIT_SIZE;
+                        while (map) {
+                                e_iter->maps[e_idx++] |= map & (-1UL);
+                                map >>= EBITMAP_UNIT_SIZE;
+                        }
                 }
                 c_iter = c_iter->next;
         } while (c_iter != NULL);
         if (e_iter != NULL)
-                ebmap->highbit = e_iter->startbit + MAPSIZE;
+                ebmap->highbit = e_iter->startbit + EBITMAP_SIZE;
         else
                 ebitmap_destroy(ebmap);
 
@@ -186,6 +214,7 @@ netlbl_import_failure:
 int ebitmap_contains(struct ebitmap *e1, struct ebitmap *e2)
 {
         struct ebitmap_node *n1, *n2;
+        int i;
 
         if (e1->highbit < e2->highbit)
                 return 0;
@@ -197,8 +226,10 @@ int ebitmap_contains(struct ebitmap *e1, struct ebitmap *e2)
                         n1 = n1->next;
                         continue;
                 }
-                if ((n1->map & n2->map) != n2->map)
-                        return 0;
+                for (i = 0; i < EBITMAP_UNIT_NUMS; i++) {
+                        if ((n1->maps[i] & n2->maps[i]) != n2->maps[i])
+                                return 0;
+                }
 
                 n1 = n1->next;
                 n2 = n2->next;
@@ -219,12 +250,8 @@ int ebitmap_get_bit(struct ebitmap *e, unsigned long bit)
 
         n = e->node;
         while (n && (n->startbit <= bit)) {
-                if ((n->startbit + MAPSIZE) > bit) {
-                        if (n->map & (MAPBIT << (bit - n->startbit)))
-                                return 1;
-                        else
-                                return 0;
-                }
+                if ((n->startbit + EBITMAP_SIZE) > bit)
+                        return ebitmap_node_get_bit(n, bit);
                 n = n->next;
         }
 
@@ -238,31 +265,35 @@ int ebitmap_set_bit(struct ebitmap *e, unsigned long bit, int value)
         prev = NULL;
         n = e->node;
         while (n && n->startbit <= bit) {
-                if ((n->startbit + MAPSIZE) > bit) {
+                if ((n->startbit + EBITMAP_SIZE) > bit) {
                         if (value) {
-                                n->map |= (MAPBIT << (bit - n->startbit));
+                                ebitmap_node_set_bit(n, bit);
                         } else {
-                                n->map &= ~(MAPBIT << (bit - n->startbit));
-                                if (!n->map) {
-                                        /* drop this node from the bitmap */
-
-                                        if (!n->next) {
-                                                /*
-                                                 * this was the highest map
-                                                 * within the bitmap
-                                                 */
-                                                if (prev)
-                                                        e->highbit = prev->startbit + MAPSIZE;
-                                                else
-                                                        e->highbit = 0;
-                                        }
+                                unsigned int s;
+
+                                ebitmap_node_clr_bit(n, bit);
+
+                                s = find_first_bit(n->maps, EBITMAP_SIZE);
+                                if (s < EBITMAP_SIZE)
+                                        return 0;
+
+                                /* drop this node from the bitmap */
+                                if (!n->next) {
+                                        /*
+                                         * this was the highest map
+                                         * within the bitmap
+                                         */
                                         if (prev)
-                                                prev->next = n->next;
+                                                e->highbit = prev->startbit
+                                                             + EBITMAP_SIZE;
                                         else
-                                                e->node = n->next;
-
-                                        kfree(n);
+                                                e->highbit = 0;
                                 }
+                                if (prev)
+                                        prev->next = n->next;
+                                else
+                                        e->node = n->next;
+                                kfree(n);
                         }
                         return 0;
                 }
@@ -277,12 +308,12 @@ int ebitmap_set_bit(struct ebitmap *e, unsigned long bit, int value)
         if (!new)
                 return -ENOMEM;
 
-        new->startbit = bit & ~(MAPSIZE - 1);
-        new->map = (MAPBIT << (bit - new->startbit));
+        new->startbit = bit - (bit % EBITMAP_SIZE);
+        ebitmap_node_set_bit(new, bit);
 
         if (!n)
                 /* this node will be the highest map within the bitmap */
-                e->highbit = new->startbit + MAPSIZE;
+                e->highbit = new->startbit + EBITMAP_SIZE;
 
         if (prev) {
                 new->next = prev->next;
@@ -316,11 +347,11 @@ void ebitmap_destroy(struct ebitmap *e)
 
 int ebitmap_read(struct ebitmap *e, void *fp)
 {
-        int rc;
-        struct ebitmap_node *n, *l;
+        struct ebitmap_node *n = NULL;
+        u32 mapunit, count, startbit, index;
+        u64 map;
         __le32 buf[3];
-        u32 mapsize, count, i;
-        __le64 map;
+        int rc, i;
 
         ebitmap_init(e);
 
@@ -328,85 +359,89 @@ int ebitmap_read(struct ebitmap *e, void *fp)
         if (rc < 0)
                 goto out;
 
-        mapsize = le32_to_cpu(buf[0]);
+        mapunit = le32_to_cpu(buf[0]);
         e->highbit = le32_to_cpu(buf[1]);
         count = le32_to_cpu(buf[2]);
 
-        if (mapsize != MAPSIZE) {
+        if (mapunit != sizeof(u64) * 8) {
                 printk(KERN_ERR "security: ebitmap: map size %u does not "
-                       "match my size %Zd (high bit was %d)\n", mapsize,
-                       MAPSIZE, e->highbit);
+                       "match my size %Zd (high bit was %d)\n",
+                       mapunit, sizeof(u64) * 8, e->highbit);
                 goto bad;
         }
+
+        /* round up e->highbit */
+        e->highbit += EBITMAP_SIZE - 1;
+        e->highbit -= (e->highbit % EBITMAP_SIZE);
+
         if (!e->highbit) {
                 e->node = NULL;
                 goto ok;
         }
-        if (e->highbit & (MAPSIZE - 1)) {
-                printk(KERN_ERR "security: ebitmap: high bit (%d) is not a "
-                       "multiple of the map size (%Zd)\n", e->highbit, MAPSIZE);
-                goto bad;
-        }
-        l = NULL;
+
         for (i = 0; i < count; i++) {
-                rc = next_entry(buf, fp, sizeof(u32));
+                rc = next_entry(&startbit, fp, sizeof(u32));
                 if (rc < 0) {
                         printk(KERN_ERR "security: ebitmap: truncated map\n");
                         goto bad;
                 }
-                n = kzalloc(sizeof(*n), GFP_KERNEL);
-                if (!n) {
-                        printk(KERN_ERR "security: ebitmap: out of memory\n");
-                        rc = -ENOMEM;
-                        goto bad;
-                }
-
-                n->startbit = le32_to_cpu(buf[0]);
+                startbit = le32_to_cpu(startbit);
 
-                if (n->startbit & (MAPSIZE - 1)) {
+                if (startbit & (mapunit - 1)) {
                         printk(KERN_ERR "security: ebitmap start bit (%d) is "
-                               "not a multiple of the map size (%Zd)\n",
-                               n->startbit, MAPSIZE);
-                        goto bad_free;
+                               "not a multiple of the map unit size (%Zd)\n",
+                               startbit, mapunit);
+                        goto bad;
                 }
-                if (n->startbit > (e->highbit - MAPSIZE)) {
+                if (startbit > e->highbit - mapunit) {
                         printk(KERN_ERR "security: ebitmap start bit (%d) is "
                                "beyond the end of the bitmap (%Zd)\n",
-                               n->startbit, (e->highbit - MAPSIZE));
-                        goto bad_free;
+                               startbit, (e->highbit - mapunit));
+                        goto bad;
+                }
+
+                if (!n || startbit >= n->startbit + EBITMAP_SIZE) {
+                        struct ebitmap_node *tmp;
+                        tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
+                        if (!tmp) {
+                                printk(KERN_ERR
+                                       "security: ebitmap: out of memory\n");
+                                rc = -ENOMEM;
+                                goto bad;
+                        }
+                        /* round down */
+                        tmp->startbit = startbit - (startbit % EBITMAP_SIZE);
+                        if (n) {
+                                n->next = tmp;
+                        } else {
+                                e->node = tmp;
+                        }
+                        n = tmp;
+                } else if (startbit <= n->startbit) {
+                        printk(KERN_ERR "security: ebitmap: start bit %d"
+                               " comes after start bit %d\n",
+                               startbit, n->startbit);
+                        goto bad;
                 }
+
                 rc = next_entry(&map, fp, sizeof(u64));
                 if (rc < 0) {
                         printk(KERN_ERR "security: ebitmap: truncated map\n");
-                        goto bad_free;
+                        goto bad;
                 }
-                n->map = le64_to_cpu(map);
+                map = le64_to_cpu(map);
 
-                if (!n->map) {
-                        printk(KERN_ERR "security: ebitmap: null map in "
-                               "ebitmap (startbit %d)\n", n->startbit);
-                        goto bad_free;
+                index = (startbit - n->startbit) / EBITMAP_UNIT_SIZE;
+                while (map) {
+                        n->maps[index] = map & (-1UL);
+                        map = map >> EBITMAP_UNIT_SIZE;
+                        index++;
                 }
-                if (l) {
-                        if (n->startbit <= l->startbit) {
-                                printk(KERN_ERR "security: ebitmap: start "
-                                       "bit %d comes after start bit %d\n",
-                                       n->startbit, l->startbit);
-                                goto bad_free;
-                        }
-                        l->next = n;
-                } else
-                        e->node = n;
-
-                l = n;
         }
-
 ok:
         rc = 0;
 out:
         return rc;
-bad_free:
-        kfree(n);
 bad:
         if (!rc)
                 rc = -EINVAL;
diff --git a/security/selinux/ss/ebitmap.h b/security/selinux/ss/ebitmap.h
index 1270e34b61c..e38a327dd70 100644
--- a/security/selinux/ss/ebitmap.h
+++ b/security/selinux/ss/ebitmap.h
@@ -16,14 +16,16 @@
 
 #include <net/netlabel.h>
 
-#define MAPTYPE u64                     /* portion of bitmap in each node */
-#define MAPSIZE (sizeof(MAPTYPE) * 8)   /* number of bits in node bitmap */
-#define MAPBIT  1ULL                    /* a bit in the node bitmap */
+#define EBITMAP_UNIT_NUMS       ((32 - sizeof(void *) - sizeof(u32))    \
+                                        / sizeof(unsigned long))
+#define EBITMAP_UNIT_SIZE       BITS_PER_LONG
+#define EBITMAP_SIZE            (EBITMAP_UNIT_NUMS * EBITMAP_UNIT_SIZE)
+#define EBITMAP_BIT             1ULL
 
 struct ebitmap_node {
-        u32 startbit;           /* starting position in the total bitmap */
-        MAPTYPE map;            /* this node's portion of the bitmap */
         struct ebitmap_node *next;
+        unsigned long maps[EBITMAP_UNIT_NUMS];
+        u32 startbit;
 };
 
 struct ebitmap {
@@ -34,11 +36,17 @@ struct ebitmap {
 #define ebitmap_length(e) ((e)->highbit)
 #define ebitmap_startbit(e) ((e)->node ? (e)->node->startbit : 0)
 
-static inline unsigned int ebitmap_start(struct ebitmap *e,
-                                         struct ebitmap_node **n)
+static inline unsigned int ebitmap_start_positive(struct ebitmap *e,
+                                                  struct ebitmap_node **n)
 {
-        *n = e->node;
-        return ebitmap_startbit(e);
+        unsigned int ofs;
+
+        for (*n = e->node; *n; *n = (*n)->next) {
+                ofs = find_first_bit((*n)->maps, EBITMAP_SIZE);
+                if (ofs < EBITMAP_SIZE)
+                        return (*n)->startbit + ofs;
+        }
+        return ebitmap_length(e);
 }
 
 static inline void ebitmap_init(struct ebitmap *e)
@@ -46,28 +54,65 @@ static inline void ebitmap_init(struct ebitmap *e)
         memset(e, 0, sizeof(*e));
 }
 
-static inline unsigned int ebitmap_next(struct ebitmap_node **n,
-                                        unsigned int bit)
+static inline unsigned int ebitmap_next_positive(struct ebitmap *e,
+                                                 struct ebitmap_node **n,
+                                                 unsigned int bit)
 {
-        if ((bit == ((*n)->startbit + MAPSIZE - 1)) &&
-            (*n)->next) {
-                *n = (*n)->next;
-                return (*n)->startbit;
-        }
+        unsigned int ofs;
+
+        ofs = find_next_bit((*n)->maps, EBITMAP_SIZE, bit - (*n)->startbit + 1);
+        if (ofs < EBITMAP_SIZE)
+                return ofs + (*n)->startbit;
 
-        return (bit+1);
+        for (*n = (*n)->next; *n; *n = (*n)->next) {
+                ofs = find_first_bit((*n)->maps, EBITMAP_SIZE);
+                if (ofs < EBITMAP_SIZE)
+                        return ofs + (*n)->startbit;
+        }
+        return ebitmap_length(e);
 }
 
-static inline int ebitmap_node_get_bit(struct ebitmap_node * n,
+#define EBITMAP_NODE_INDEX(node, bit)   \
+        (((bit) - (node)->startbit) / EBITMAP_UNIT_SIZE)
+#define EBITMAP_NODE_OFFSET(node, bit)  \
+        (((bit) - (node)->startbit) % EBITMAP_UNIT_SIZE)
+
+static inline int ebitmap_node_get_bit(struct ebitmap_node *n,
                                        unsigned int bit)
 {
-        if (n->map & (MAPBIT << (bit - n->startbit)))
+        unsigned int index = EBITMAP_NODE_INDEX(n, bit);
+        unsigned int ofs = EBITMAP_NODE_OFFSET(n, bit);
+
+        BUG_ON(index >= EBITMAP_UNIT_NUMS);
+        if ((n->maps[index] & (EBITMAP_BIT << ofs)))
                 return 1;
         return 0;
 }
 
-#define ebitmap_for_each_bit(e, n, bit) \
-        for (bit = ebitmap_start(e, &n); bit < ebitmap_length(e); bit = ebitmap_next(&n, bit)) \
+static inline void ebitmap_node_set_bit(struct ebitmap_node *n,
+                                        unsigned int bit)
+{
+        unsigned int index = EBITMAP_NODE_INDEX(n, bit);
+        unsigned int ofs = EBITMAP_NODE_OFFSET(n, bit);
+
+        BUG_ON(index >= EBITMAP_UNIT_NUMS);
+        n->maps[index] |= (EBITMAP_BIT << ofs);
+}
+
+static inline void ebitmap_node_clr_bit(struct ebitmap_node *n,
+                                        unsigned int bit)
+{
+        unsigned int index = EBITMAP_NODE_INDEX(n, bit);
+        unsigned int ofs = EBITMAP_NODE_OFFSET(n, bit);
+
+        BUG_ON(index >= EBITMAP_UNIT_NUMS);
+        n->maps[index] &= ~(EBITMAP_BIT << ofs);
+}
+
+#define ebitmap_for_each_positive_bit(e, n, bit)        \
+        for (bit = ebitmap_start_positive(e, &n);       \
+             bit < ebitmap_length(e);                   \
+             bit = ebitmap_next_positive(e, &n, bit))   \
 
 int ebitmap_cmp(struct ebitmap *e1, struct ebitmap *e2);
 int ebitmap_cpy(struct ebitmap *dst, struct ebitmap *src);
diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index 4a8bab2f3c7..9a11deaaa9e 100644
--- a/security/selinux/ss/mls.c
+++ b/security/selinux/ss/mls.c
@@ -34,7 +34,9 @@
  */
 int mls_compute_context_len(struct context * context)
 {
-        int i, l, len, range;
+        int i, l, len, head, prev;
+        char *nm;
+        struct ebitmap *e;
         struct ebitmap_node *node;
 
         if (!selinux_mls_enabled)
@@ -42,31 +44,33 @@ int mls_compute_context_len(struct context * context)
 
         len = 1; /* for the beginning ":" */
         for (l = 0; l < 2; l++) {
-                range = 0;
-                len += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
-
-                ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
-                        if (ebitmap_node_get_bit(node, i)) {
-                                if (range) {
-                                        range++;
-                                        continue;
-                                }
+                int index_sens = context->range.level[l].sens;
+                len += strlen(policydb.p_sens_val_to_name[index_sens - 1]);
 
-                                len += strlen(policydb.p_cat_val_to_name[i]) + 1;
-                                range++;
-                        } else {
-                                if (range > 1)
-                                        len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
-                                range = 0;
+                /* categories */
+                head = -2;
+                prev = -2;
+                e = &context->range.level[l].cat;
+                ebitmap_for_each_positive_bit(e, node, i) {
+                        if (i - prev > 1) {
+                                /* one or more negative bits are skipped */
+                                if (head != prev) {
+                                        nm = policydb.p_cat_val_to_name[prev];
+                                        len += strlen(nm) + 1;
+                                }
+                                nm = policydb.p_cat_val_to_name[i];
+                                len += strlen(nm) + 1;
+                                head = i;
                         }
+                        prev = i;
+                }
+                if (prev != head) {
+                        nm = policydb.p_cat_val_to_name[prev];
+                        len += strlen(nm) + 1;
                 }
-                /* Handle case where last category is the end of range */
-                if (range > 1)
-                        len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
-
                 if (l == 0) {
                         if (mls_level_eq(&context->range.level[0],
-                                         &context->range.level[1]))
+                                         &context->range.level[1]))
                                 break;
                         else
                                 len++;
@@ -84,8 +88,9 @@ int mls_compute_context_len(struct context * context)
 void mls_sid_to_context(struct context *context,
                         char **scontext)
 {
-        char *scontextp;
-        int i, l, range, wrote_sep;
+        char *scontextp, *nm;
+        int i, l, head, prev;
+        struct ebitmap *e;
         struct ebitmap_node *node;
 
         if (!selinux_mls_enabled)
@@ -97,61 +102,54 @@ void mls_sid_to_context(struct context *context,
         scontextp++;
 
         for (l = 0; l < 2; l++) {
-                range = 0;
-                wrote_sep = 0;
                 strcpy(scontextp,
                        policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
-                scontextp += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
+                scontextp += strlen(scontextp);
 
                 /* categories */
-                ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
-                        if (ebitmap_node_get_bit(node, i)) {
-                                if (range) {
-                                        range++;
-                                        continue;
-                                }
-
-                                if (!wrote_sep) {
-                                        *scontextp++ = ':';
-                                        wrote_sep = 1;
-                                } else
-                                        *scontextp++ = ',';
-                                strcpy(scontextp, policydb.p_cat_val_to_name[i]);
-                                scontextp += strlen(policydb.p_cat_val_to_name[i]);
-                                range++;
-                        } else {
-                                if (range > 1) {
-                                        if (range > 2)
+                head = -2;
+                prev = -2;
+                e = &context->range.level[l].cat;
+                ebitmap_for_each_positive_bit(e, node, i) {
+                        if (i - prev > 1) {
+                                /* one or more negative bits are skipped */
+                                if (prev != head) {
+                                        if (prev - head > 1)
                                                 *scontextp++ = '.';
                                         else
                                                 *scontextp++ = ',';
-
-                                        strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
-                                        scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
+                                        nm = policydb.p_cat_val_to_name[prev];
+                                        strcpy(scontextp, nm);
+                                        scontextp += strlen(nm);
                                 }
-                                range = 0;
+                                if (prev < 0)
+                                        *scontextp++ = ':';
+                                else
+                                        *scontextp++ = ',';
+                                nm = policydb.p_cat_val_to_name[i];
+                                strcpy(scontextp, nm);
+                                scontextp += strlen(nm);
+                                head = i;
                         }
+                        prev = i;
                 }
 
-                /* Handle case where last category is the end of range */
-                if (range > 1) {
-                        if (range > 2)
+                if (prev != head) {
+                        if (prev - head > 1)
                                 *scontextp++ = '.';
                         else
                                 *scontextp++ = ',';
-
-                        strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
-                        scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
+                        nm = policydb.p_cat_val_to_name[prev];
+                        strcpy(scontextp, nm);
+                        scontextp += strlen(nm);
                 }
 
                 if (l == 0) {
                         if (mls_level_eq(&context->range.level[0],
                                          &context->range.level[1]))
                                 break;
-                        else {
-                                *scontextp = '-';
-                                scontextp++;
-                        }
+                        else
+                                *scontextp++ = '-';
                 }
         }
 
@@ -190,17 +188,15 @@ int mls_context_isvalid(struct policydb *p, struct context *c)
                 if (!levdatum)
                         return 0;
 
-                ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
-                        if (ebitmap_node_get_bit(node, i)) {
-                                if (i > p->p_cats.nprim)
-                                        return 0;
-                                if (!ebitmap_get_bit(&levdatum->level->cat, i))
-                                        /*
-                                         * Category may not be associated with
-                                         * sensitivity in low level.
-                                         */
-                                        return 0;
-                        }
+                ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
+                        if (i > p->p_cats.nprim)
+                                return 0;
+                        if (!ebitmap_get_bit(&levdatum->level->cat, i))
+                                /*
+                                 * Category may not be associated with
+                                 * sensitivity in low level.
+                                 */
+                                return 0;
                 }
         }
 
@@ -485,18 +481,16 @@ int mls_convert_context(struct policydb *oldp,
                 c->range.level[l].sens = levdatum->level->sens;
 
                 ebitmap_init(&bitmap);
-                ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
-                        if (ebitmap_node_get_bit(node, i)) {
-                                int rc;
-
-                                catdatum = hashtab_search(newp->p_cats.table,
-                                                oldp->p_cat_val_to_name[i]);
-                                if (!catdatum)
-                                        return -EINVAL;
-                                rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
-                                if (rc)
-                                        return rc;
-                        }
+                ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
+                        int rc;
+
+                        catdatum = hashtab_search(newp->p_cats.table,
+                                                  oldp->p_cat_val_to_name[i]);
+                        if (!catdatum)
+                                return -EINVAL;
+                        rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
+                        if (rc)
+                                return rc;
                 }
                 ebitmap_destroy(&c->range.level[l].cat);
                 c->range.level[l].cat = bitmap;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 03140edf97a..d572dc908f3 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -353,12 +353,8 @@ static int context_struct_compute_av(struct context *scontext,
         avkey.specified = AVTAB_AV;
         sattr = &policydb.type_attr_map[scontext->type - 1];
         tattr = &policydb.type_attr_map[tcontext->type - 1];
-        ebitmap_for_each_bit(sattr, snode, i) {
-                if (!ebitmap_node_get_bit(snode, i))
-                        continue;
-                ebitmap_for_each_bit(tattr, tnode, j) {
-                        if (!ebitmap_node_get_bit(tnode, j))
-                                continue;
+        ebitmap_for_each_positive_bit(sattr, snode, i) {
+                ebitmap_for_each_positive_bit(tattr, tnode, j) {
                         avkey.source_type = i + 1;
                         avkey.target_type = j + 1;
                         for (node = avtab_search_node(&policydb.te_avtab, &avkey);
@@ -1668,14 +1664,10 @@ int security_get_user_sids(u32 fromsid,
                 goto out_unlock;
         }
 
-        ebitmap_for_each_bit(&user->roles, rnode, i) {
-                if (!ebitmap_node_get_bit(rnode, i))
-                        continue;
+        ebitmap_for_each_positive_bit(&user->roles, rnode, i) {
                 role = policydb.role_val_to_struct[i];
                 usercon.role = i+1;
-                ebitmap_for_each_bit(&role->types, tnode, j) {
-                        if (!ebitmap_node_get_bit(tnode, j))
-                                continue;
+                ebitmap_for_each_positive_bit(&role->types, tnode, j) {
                         usercon.type = j+1;
 
                         if (mls_setup_user_range(fromcon, user, &usercon))