groups: move code to kernel/groups.c

Move supplementary groups implementation to kernel/groups.c .
kernel/sys.c already accumulated quite a few random stuff.

Do strictly copy/paste + add required headers to compile.  Compile-tested
on many configs and archs.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 288 insertions, 0 deletions

diff --git a/kernel/groups.c b/kernel/groups.c
new file mode 100644
index 000000000000..2b45b2ee3964
--- /dev/null
+++ b/kernel/groups.c
@@ -0,0 +1,288 @@
+/*
+ * Supplementary group IDs
+ */
+#include <linux/cred.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <asm/uaccess.h>
+
+/* init to 2 - one for init_task, one to ensure it is never freed */
+struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
+
+struct group_info *groups_alloc(int gidsetsize)
+{
+        struct group_info *group_info;
+        int nblocks;
+        int i;
+
+        nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
+        /* Make sure we always allocate at least one indirect block pointer */
+        nblocks = nblocks ? : 1;
+        group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
+        if (!group_info)
+                return NULL;
+        group_info->ngroups = gidsetsize;
+        group_info->nblocks = nblocks;
+        atomic_set(&group_info->usage, 1);
+
+        if (gidsetsize <= NGROUPS_SMALL)
+                group_info->blocks[0] = group_info->small_block;
+        else {
+                for (i = 0; i < nblocks; i++) {
+                        gid_t *b;
+                        b = (void *)__get_free_page(GFP_USER);
+                        if (!b)
+                                goto out_undo_partial_alloc;
+                        group_info->blocks[i] = b;
+                }
+        }
+        return group_info;
+
+out_undo_partial_alloc:
+        while (--i >= 0) {
+                free_page((unsigned long)group_info->blocks[i]);
+        }
+        kfree(group_info);
+        return NULL;
+}
+
+EXPORT_SYMBOL(groups_alloc);
+
+void groups_free(struct group_info *group_info)
+{
+        if (group_info->blocks[0] != group_info->small_block) {
+                int i;
+                for (i = 0; i < group_info->nblocks; i++)
+                        free_page((unsigned long)group_info->blocks[i]);
+        }
+        kfree(group_info);
+}
+
+EXPORT_SYMBOL(groups_free);
+
+/* export the group_info to a user-space array */
+static int groups_to_user(gid_t __user *grouplist,
+                          const struct group_info *group_info)
+{
+        int i;
+        unsigned int count = group_info->ngroups;
+
+        for (i = 0; i < group_info->nblocks; i++) {
+                unsigned int cp_count = min(NGROUPS_PER_BLOCK, count);
+                unsigned int len = cp_count * sizeof(*grouplist);
+
+                if (copy_to_user(grouplist, group_info->blocks[i], len))
+                        return -EFAULT;
+
+                grouplist += NGROUPS_PER_BLOCK;
+                count -= cp_count;
+        }
+        return 0;
+}
+
+/* fill a group_info from a user-space array - it must be allocated already */
+static int groups_from_user(struct group_info *group_info,
+    gid_t __user *grouplist)
+{
+        int i;
+        unsigned int count = group_info->ngroups;
+
+        for (i = 0; i < group_info->nblocks; i++) {
+                unsigned int cp_count = min(NGROUPS_PER_BLOCK, count);
+                unsigned int len = cp_count * sizeof(*grouplist);
+
+                if (copy_from_user(group_info->blocks[i], grouplist, len))
+                        return -EFAULT;
+
+                grouplist += NGROUPS_PER_BLOCK;
+                count -= cp_count;
+        }
+        return 0;
+}
+
+/* a simple Shell sort */
+static void groups_sort(struct group_info *group_info)
+{
+        int base, max, stride;
+        int gidsetsize = group_info->ngroups;
+
+        for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
+                ; /* nothing */
+        stride /= 3;
+
+        while (stride) {
+                max = gidsetsize - stride;
+                for (base = 0; base < max; base++) {
+                        int left = base;
+                        int right = left + stride;
+                        gid_t tmp = GROUP_AT(group_info, right);
+
+                        while (left >= 0 && GROUP_AT(group_info, left) > tmp) {
+                                GROUP_AT(group_info, right) =
+                                    GROUP_AT(group_info, left);
+                                right = left;
+                                left -= stride;
+                        }
+                        GROUP_AT(group_info, right) = tmp;
+                }
+                stride /= 3;
+        }
+}
+
+/* a simple bsearch */
+int groups_search(const struct group_info *group_info, gid_t grp)
+{
+        unsigned int left, right;
+
+        if (!group_info)
+                return 0;
+
+        left = 0;
+        right = group_info->ngroups;
+        while (left < right) {
+                unsigned int mid = (left+right)/2;
+                int cmp = grp - GROUP_AT(group_info, mid);
+                if (cmp > 0)
+                        left = mid + 1;
+                else if (cmp < 0)
+                        right = mid;
+                else
+                        return 1;
+        }
+        return 0;
+}
+
+/**
+ * set_groups - Change a group subscription in a set of credentials
+ * @new: The newly prepared set of credentials to alter
+ * @group_info: The group list to install
+ *
+ * Validate a group subscription and, if valid, insert it into a set
+ * of credentials.
+ */
+int set_groups(struct cred *new, struct group_info *group_info)
+{
+        int retval;
+
+        retval = security_task_setgroups(group_info);
+        if (retval)
+                return retval;
+
+        put_group_info(new->group_info);
+        groups_sort(group_info);
+        get_group_info(group_info);
+        new->group_info = group_info;
+        return 0;
+}
+
+EXPORT_SYMBOL(set_groups);
+
+/**
+ * set_current_groups - Change current's group subscription
+ * @group_info: The group list to impose
+ *
+ * Validate a group subscription and, if valid, impose it upon current's task
+ * security record.
+ */
+int set_current_groups(struct group_info *group_info)
+{
+        struct cred *new;
+        int ret;
+
+        new = prepare_creds();
+        if (!new)
+                return -ENOMEM;
+
+        ret = set_groups(new, group_info);
+        if (ret < 0) {
+                abort_creds(new);
+                return ret;
+        }
+
+        return commit_creds(new);
+}
+
+EXPORT_SYMBOL(set_current_groups);
+
+SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
+{
+        const struct cred *cred = current_cred();
+        int i;
+
+        if (gidsetsize < 0)
+                return -EINVAL;
+
+        /* no need to grab task_lock here; it cannot change */
+        i = cred->group_info->ngroups;
+        if (gidsetsize) {
+                if (i > gidsetsize) {
+                        i = -EINVAL;
+                        goto out;
+                }
+                if (groups_to_user(grouplist, cred->group_info)) {
+                        i = -EFAULT;
+                        goto out;
+                }
+        }
+out:
+        return i;
+}
+
+/*
+ *      SMP: Our groups are copy-on-write. We can set them safely
+ *      without another task interfering.
+ */
+
+SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
+{
+        struct group_info *group_info;
+        int retval;
+
+        if (!capable(CAP_SETGID))
+                return -EPERM;
+        if ((unsigned)gidsetsize > NGROUPS_MAX)
+                return -EINVAL;
+
+        group_info = groups_alloc(gidsetsize);
+        if (!group_info)
+                return -ENOMEM;
+        retval = groups_from_user(group_info, grouplist);
+        if (retval) {
+                put_group_info(group_info);
+                return retval;
+        }
+
+        retval = set_current_groups(group_info);
+        put_group_info(group_info);
+
+        return retval;
+}
+
+/*
+ * Check whether we're fsgid/egid or in the supplemental group..
+ */
+int in_group_p(gid_t grp)
+{
+        const struct cred *cred = current_cred();
+        int retval = 1;
+
+        if (grp != cred->fsgid)
+                retval = groups_search(cred->group_info, grp);
+        return retval;
+}
+
+EXPORT_SYMBOL(in_group_p);
+
+int in_egroup_p(gid_t grp)
+{
+        const struct cred *cred = current_cred();
+        int retval = 1;
+
+        if (grp != cred->egid)
+                retval = groups_search(cred->group_info, grp);
+        return retval;
+}
+
+EXPORT_SYMBOL(in_egroup_p);