diff options
Diffstat (limited to 'kernel/groups.c')
| -rw-r--r-- | kernel/groups.c | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/kernel/groups.c b/kernel/groups.c new file mode 100644 index 000000000..fe7e63855 --- /dev/null +++ b/kernel/groups.c @@ -0,0 +1,241 @@ +// 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; + unsigned int len; + + len = sizeof(struct group_info) + sizeof(kgid_t) * gidsetsize; + gi = kmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_NOWARN|__GFP_NORETRY); + if (!gi) + gi = __vmalloc(len, 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); |