Как одурачить всех вокруг⁠⁠

если до конца тыкать на кнопки то напишется вот такой код :)
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 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;

if (grp > GROUP_AT(group_info, mid))

left = mid + 1;

else if (grp < GROUP_AT(group_info, 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

*

* 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)

{

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 (!nsown_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;

}