1 files changed, 291 insertions, 58 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index d32b45662fb6..246d4d4ce5c7 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -23,6 +23,8 @@
 #include <linux/ctype.h>
 #include <linux/projid.h>
 #include <linux/fs_struct.h>
+#include <linux/bsearch.h>
+#include <linux/sort.h>
 
 static struct kmem_cache *user_ns_cachep __read_mostly;
 static DEFINE_MUTEX(userns_state_mutex);
@@ -181,6 +183,18 @@ static void free_user_ns(struct work_struct *work)
         do {
                 struct ucounts *ucounts = ns->ucounts;
                 parent = ns->parent;
+                if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
+                        kfree(ns->gid_map.forward);
+                        kfree(ns->gid_map.reverse);
+                }
+                if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
+                        kfree(ns->uid_map.forward);
+                        kfree(ns->uid_map.reverse);
+                }
+                if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
+                        kfree(ns->projid_map.forward);
+                        kfree(ns->projid_map.reverse);
+                }
                 retire_userns_sysctls(ns);
 #ifdef CONFIG_PERSISTENT_KEYRINGS
                 key_put(ns->persistent_keyring_register);
@@ -198,26 +212,101 @@ void __put_user_ns(struct user_namespace *ns)
 }
 EXPORT_SYMBOL(__put_user_ns);
 
-static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
+/**
+ * idmap_key struct holds the information necessary to find an idmapping in a
+ * sorted idmap array. It is passed to cmp_map_id() as first argument.
+ */
+struct idmap_key {
+        bool map_up; /* true  -> id from kid; false -> kid from id */
+        u32 id; /* id to find */
+        u32 count; /* == 0 unless used with map_id_range_down() */
+};
+
+/**
+ * cmp_map_id - Function to be passed to bsearch() to find the requested
+ * idmapping. Expects struct idmap_key to be passed via @k.
+ */
+static int cmp_map_id(const void *k, const void *e)
 {
-        unsigned idx, extents;
+        u32 first, last, id2;
+        const struct idmap_key *key = k;
+        const struct uid_gid_extent *el = e;
+
+        id2 = key->id + key->count - 1;
+
+        /* handle map_id_{down,up}() */
+        if (key->map_up)
+                first = el->lower_first;
+        else
+                first = el->first;
+
+        last = first + el->count - 1;
+
+        if (key->id >= first && key->id <= last &&
+            (id2 >= first && id2 <= last))
+                return 0;
+
+        if (key->id < first || id2 < first)
+                return -1;
+
+        return 1;
+}
+
+/**
+ * map_id_range_down_max - Find idmap via binary search in ordered idmap array.
+ * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
+ */
+static struct uid_gid_extent *
+map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
+{
+        struct idmap_key key;
+
+        key.map_up = false;
+        key.count = count;
+        key.id = id;
+
+        return bsearch(&key, map->forward, extents,
+                       sizeof(struct uid_gid_extent), cmp_map_id);
+}
+
+/**
+ * map_id_range_down_base - Find idmap via binary search in static extent array.
+ * Can only be called if number of mappings is equal or less than
+ * UID_GID_MAP_MAX_BASE_EXTENTS.
+ */
+static struct uid_gid_extent *
+map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
+{
+        unsigned idx;
         u32 first, last, id2;
 
         id2 = id + count - 1;
 
         /* Find the matching extent */
-        extents = map->nr_extents;
-        smp_rmb();
         for (idx = 0; idx < extents; idx++) {
                 first = map->extent[idx].first;
                 last = first + map->extent[idx].count - 1;
                 if (id >= first && id <= last &&
                     (id2 >= first && id2 <= last))
-                        break;
+                        return &map->extent[idx];
         }
+        return NULL;
+}
+
+static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
+{
+        struct uid_gid_extent *extent;
+        unsigned extents = map->nr_extents;
+        smp_rmb();
+
+        if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+                extent = map_id_range_down_base(extents, map, id, count);
+        else
+                extent = map_id_range_down_max(extents, map, id, count);
+
         /* Map the id or note failure */
-        if (idx < extents)
-                id = (id - first) + map->extent[idx].lower_first;
+        if (extent)
+                id = (id - extent->first) + extent->lower_first;
         else
                 id = (u32) -1;
 
@@ -226,44 +315,61 @@ static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
 
 static u32 map_id_down(struct uid_gid_map *map, u32 id)
 {
-        unsigned idx, extents;
+        return map_id_range_down(map, id, 1);
+}
+
+/**
+ * map_id_up_base - Find idmap via binary search in static extent array.
+ * Can only be called if number of mappings is equal or less than
+ * UID_GID_MAP_MAX_BASE_EXTENTS.
+ */
+static struct uid_gid_extent *
+map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
+{
+        unsigned idx;
         u32 first, last;
 
         /* Find the matching extent */
-        extents = map->nr_extents;
-        smp_rmb();
         for (idx = 0; idx < extents; idx++) {
-                first = map->extent[idx].first;
+                first = map->extent[idx].lower_first;
                 last = first + map->extent[idx].count - 1;
                 if (id >= first && id <= last)
-                        break;
+                        return &map->extent[idx];
         }
-        /* Map the id or note failure */
-        if (idx < extents)
-                id = (id - first) + map->extent[idx].lower_first;
-        else
-                id = (u32) -1;
+        return NULL;
+}
 
-        return id;
+/**
+ * map_id_up_max - Find idmap via binary search in ordered idmap array.
+ * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
+ */
+static struct uid_gid_extent *
+map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
+{
+        struct idmap_key key;
+
+        key.map_up = true;
+        key.count = 1;
+        key.id = id;
+
+        return bsearch(&key, map->reverse, extents,
+                       sizeof(struct uid_gid_extent), cmp_map_id);
 }
 
 static u32 map_id_up(struct uid_gid_map *map, u32 id)
 {
-        unsigned idx, extents;
-        u32 first, last;
-
-        /* Find the matching extent */
-        extents = map->nr_extents;
+        struct uid_gid_extent *extent;
+        unsigned extents = map->nr_extents;
         smp_rmb();
-        for (idx = 0; idx < extents; idx++) {
-                first = map->extent[idx].lower_first;
-                last = first + map->extent[idx].count - 1;
-                if (id >= first && id <= last)
-                        break;
-        }
+
+        if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+                extent = map_id_up_base(extents, map, id);
+        else
+                extent = map_id_up_max(extents, map, id);
+
         /* Map the id or note failure */
-        if (idx < extents)
-                id = (id - first) + map->extent[idx].first;
+        if (extent)
+                id = (id - extent->lower_first) + extent->first;
         else
                 id = (u32) -1;
 
@@ -540,13 +646,17 @@ static int projid_m_show(struct seq_file *seq, void *v)
 static void *m_start(struct seq_file *seq, loff_t *ppos,
                      struct uid_gid_map *map)
 {
-        struct uid_gid_extent *extent = NULL;
         loff_t pos = *ppos;
+        unsigned extents = map->nr_extents;
+        smp_rmb();
 
-        if (pos < map->nr_extents)
-                extent = &map->extent[pos];
+        if (pos >= extents)
+                return NULL;
 
-        return extent;
+        if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+                return &map->extent[pos];
+
+        return &map->forward[pos];
 }
 
 static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
@@ -618,7 +728,10 @@ static bool mappings_overlap(struct uid_gid_map *new_map,
                 u32 prev_upper_last, prev_lower_last;
                 struct uid_gid_extent *prev;
 
-                prev = &new_map->extent[idx];
+                if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+                        prev = &new_map->extent[idx];
+                else
+                        prev = &new_map->forward[idx];
 
                 prev_upper_first = prev->first;
                 prev_lower_first = prev->lower_first;
@@ -638,6 +751,101 @@ static bool mappings_overlap(struct uid_gid_map *new_map,
         return false;
 }
 
+/**
+ * insert_extent - Safely insert a new idmap extent into struct uid_gid_map.
+ * Takes care to allocate a 4K block of memory if the number of mappings exceeds
+ * UID_GID_MAP_MAX_BASE_EXTENTS.
+ */
+static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent)
+{
+        struct uid_gid_extent *dest;
+
+        if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) {
+                struct uid_gid_extent *forward;
+
+                /* Allocate memory for 340 mappings. */
+                forward = kmalloc(sizeof(struct uid_gid_extent) *
+                                 UID_GID_MAP_MAX_EXTENTS, GFP_KERNEL);
+                if (!forward)
+                        return -ENOMEM;
+
+                /* Copy over memory. Only set up memory for the forward pointer.
+                 * Defer the memory setup for the reverse pointer.
+                 */
+                memcpy(forward, map->extent,
+                       map->nr_extents * sizeof(map->extent[0]));
+
+                map->forward = forward;
+                map->reverse = NULL;
+        }
+
+        if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS)
+                dest = &map->extent[map->nr_extents];
+        else
+                dest = &map->forward[map->nr_extents];
+
+        *dest = *extent;
+        map->nr_extents++;
+        return 0;
+}
+
+/* cmp function to sort() forward mappings */
+static int cmp_extents_forward(const void *a, const void *b)
+{
+        const struct uid_gid_extent *e1 = a;
+        const struct uid_gid_extent *e2 = b;
+
+        if (e1->first < e2->first)
+                return -1;
+
+        if (e1->first > e2->first)
+                return 1;
+
+        return 0;
+}
+
+/* cmp function to sort() reverse mappings */
+static int cmp_extents_reverse(const void *a, const void *b)
+{
+        const struct uid_gid_extent *e1 = a;
+        const struct uid_gid_extent *e2 = b;
+
+        if (e1->lower_first < e2->lower_first)
+                return -1;
+
+        if (e1->lower_first > e2->lower_first)
+                return 1;
+
+        return 0;
+}
+
+/**
+ * sort_idmaps - Sorts an array of idmap entries.
+ * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
+ */
+static int sort_idmaps(struct uid_gid_map *map)
+{
+        if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+                return 0;
+
+        /* Sort forward array. */
+        sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent),
+             cmp_extents_forward, NULL);
+
+        /* Only copy the memory from forward we actually need. */
+        map->reverse = kmemdup(map->forward,
+                               map->nr_extents * sizeof(struct uid_gid_extent),
+                               GFP_KERNEL);
+        if (!map->reverse)
+                return -ENOMEM;
+
+        /* Sort reverse array. */
+        sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent),
+             cmp_extents_reverse, NULL);
+
+        return 0;
+}
+
 static ssize_t map_write(struct file *file, const char __user *buf,
                          size_t count, loff_t *ppos,
                          int cap_setid,
@@ -648,7 +856,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
         struct user_namespace *ns = seq->private;
         struct uid_gid_map new_map;
         unsigned idx;
-        struct uid_gid_extent *extent = NULL;
+        struct uid_gid_extent extent;
         char *kbuf = NULL, *pos, *next_line;
         ssize_t ret = -EINVAL;
 
@@ -673,6 +881,8 @@ static ssize_t map_write(struct file *file, const char __user *buf,
          */
         mutex_lock(&userns_state_mutex);
 
+        memset(&new_map, 0, sizeof(struct uid_gid_map));
+
         ret = -EPERM;
         /* Only allow one successful write to the map */
         if (map->nr_extents != 0)
@@ -700,9 +910,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
         /* Parse the user data */
         ret = -EINVAL;
         pos = kbuf;
-        new_map.nr_extents = 0;
         for (; pos; pos = next_line) {
-                extent = &new_map.extent[new_map.nr_extents];
 
                 /* Find the end of line and ensure I don't look past it */
                 next_line = strchr(pos, '\n');
@@ -714,17 +922,17 @@ static ssize_t map_write(struct file *file, const char __user *buf,
                 }
 
                 pos = skip_spaces(pos);
-                extent->first = simple_strtoul(pos, &pos, 10);
+                extent.first = simple_strtoul(pos, &pos, 10);
                 if (!isspace(*pos))
                         goto out;
 
                 pos = skip_spaces(pos);
-                extent->lower_first = simple_strtoul(pos, &pos, 10);
+                extent.lower_first = simple_strtoul(pos, &pos, 10);
                 if (!isspace(*pos))
                         goto out;
 
                 pos = skip_spaces(pos);
-                extent->count = simple_strtoul(pos, &pos, 10);
+                extent.count = simple_strtoul(pos, &pos, 10);
                 if (*pos && !isspace(*pos))
                         goto out;
 
@@ -734,29 +942,31 @@ static ssize_t map_write(struct file *file, const char __user *buf,
                         goto out;
 
                 /* Verify we have been given valid starting values */
-                if ((extent->first == (u32) -1) ||
-                    (extent->lower_first == (u32) -1))
+                if ((extent.first == (u32) -1) ||
+                    (extent.lower_first == (u32) -1))
                         goto out;
 
                 /* Verify count is not zero and does not cause the
                  * extent to wrap
                  */
-                if ((extent->first + extent->count) <= extent->first)
+                if ((extent.first + extent.count) <= extent.first)
                         goto out;
-                if ((extent->lower_first + extent->count) <=
-                     extent->lower_first)
+                if ((extent.lower_first + extent.count) <=
+                     extent.lower_first)
                         goto out;
 
                 /* Do the ranges in extent overlap any previous extents? */
-                if (mappings_overlap(&new_map, extent))
+                if (mappings_overlap(&new_map, &extent))
                         goto out;
 
-                new_map.nr_extents++;
-
-                /* Fail if the file contains too many extents */
-                if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
+                if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS &&
                     (next_line != NULL))
                         goto out;
+
+                ret = insert_extent(&new_map, &extent);
+                if (ret < 0)
+                        goto out;
+                ret = -EINVAL;
         }
         /* Be very certaint the new map actually exists */
         if (new_map.nr_extents == 0)
@@ -767,16 +977,26 @@ static ssize_t map_write(struct file *file, const char __user *buf,
         if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
                 goto out;
 
+        ret = sort_idmaps(&new_map);
+        if (ret < 0)
+                goto out;
+
+        ret = -EPERM;
         /* Map the lower ids from the parent user namespace to the
          * kernel global id space.
          */
         for (idx = 0; idx < new_map.nr_extents; idx++) {
+                struct uid_gid_extent *e;
                 u32 lower_first;
-                extent = &new_map.extent[idx];
+
+                if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+                        e = &new_map.extent[idx];
+                else
+                        e = &new_map.forward[idx];
 
                 lower_first = map_id_range_down(parent_map,
-                                                extent->lower_first,
-                                                extent->count);
+                                                e->lower_first,
+                                                e->count);
 
                 /* Fail if we can not map the specified extent to
                  * the kernel global id space.
@@ -784,18 +1004,31 @@ static ssize_t map_write(struct file *file, const char __user *buf,
                 if (lower_first == (u32) -1)
                         goto out;
 
-                extent->lower_first = lower_first;
+                e->lower_first = lower_first;
         }
 
         /* Install the map */
-        memcpy(map->extent, new_map.extent,
-                new_map.nr_extents*sizeof(new_map.extent[0]));
+        if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
+                memcpy(map->extent, new_map.extent,
+                       new_map.nr_extents * sizeof(new_map.extent[0]));
+        } else {
+                map->forward = new_map.forward;
+                map->reverse = new_map.reverse;
+        }
         smp_wmb();
         map->nr_extents = new_map.nr_extents;
 
         *ppos = count;
         ret = count;
 out:
+        if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
+                kfree(new_map.forward);
+                kfree(new_map.reverse);
+                map->forward = NULL;
+                map->reverse = NULL;
+                map->nr_extents = 0;
+        }
+
         mutex_unlock(&userns_state_mutex);
         kfree(kbuf);
         return ret;