// SPDX-License-Identifier: GPL-2.0
/*
 * Supplementary group IDs
 */
#include <linux/cred.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/sort.h>
#include <linux/syscalls.h>
#include <linux/user_namespace.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>

struct group_info *groups_alloc(int gidsetsize)
{
        struct group_info *gi;
        gi = kvmalloc(struct_size(gi, gid, gidsetsize), GFP_KERNEL_ACCOUNT);
        if (!gi)
                return NULL;

        atomic_set(&gi->usage, 1);
        gi->ngroups = gidsetsize;
        return gi;
}

EXPORT_SYMBOL(groups_alloc);

void groups_free(struct group_info *group_info)
{
        kvfree(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)
{
        struct user_namespace *user_ns = current_user_ns();
        int i;
        unsigned int count = group_info->ngroups;

        for (i = 0; i < count; i++) {
                gid_t gid;
                gid = from_kgid_munged(user_ns, group_info->gid[i]);
                if (put_user(gid, grouplist+i))
                        return -EFAULT;
        }
        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)
{
        struct user_namespace *user_ns = current_user_ns();
        int i;
        unsigned int count = group_info->ngroups;

        for (i = 0; i < count; i++) {
                gid_t gid;
                kgid_t kgid;
                if (get_user(gid, grouplist+i))
                        return -EFAULT;

                kgid = make_kgid(user_ns, gid);
                if (!gid_valid(kgid))
                        return -EINVAL;

                group_info->gid[i] = kgid;
        }
        return 0;
}

static int gid_cmp(const void *_a, const void *_b)
{
        kgid_t a = *(kgid_t *)_a;
        kgid_t b = *(kgid_t *)_b;

        return gid_gt(a, b) - gid_lt(a, b);
}

void groups_sort(struct group_info *group_info)
{
        sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid),
             gid_cmp, NULL);
}
EXPORT_SYMBOL(groups_sort);

/* a simple bsearch */
int groups_search(const struct group_info *group_info, kgid_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;
                if (gid_gt(grp, group_info->gid[mid]))
                        left = mid + 1;
                else if (gid_lt(grp, group_info->gid[mid]))
                        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
 */
void set_groups(struct cred *new, struct group_info *group_info)
{
        put_group_info(new->group_info);
        get_group_info(group_info);
        new->group_info = group_info;
}

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;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        set_groups(new, group_info);
        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;
}

bool may_setgroups(void)
{
        struct user_namespace *user_ns = current_user_ns();

        return ns_capable_setid(user_ns, CAP_SETGID) &&
                userns_may_setgroups(user_ns);
}

/*
 *      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 (!may_setgroups())
                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;
        }

        groups_sort(group_info);
        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(kgid_t grp)
{
        const struct cred *cred = current_cred();
        int retval = 1;

        if (!gid_eq(grp, cred->fsgid))
                retval = groups_search(cred->group_info, grp);
        return retval;
}

EXPORT_SYMBOL(in_group_p);

int in_egroup_p(kgid_t grp)
{
        const struct cred *cred = current_cred();
        int retval = 1;

        if (!gid_eq(grp, cred->egid))
                retval = groups_search(cred->group_info, grp);
        return retval;
}

EXPORT_SYMBOL(in_egroup_p);