// SPDX-License-Identifier: GPL-2.0

/*

 * linux/ipc/util.c

 * Copyright (C) 1992 Krishna Balasubramanian

 *

 * Sep 1997 - Call suser() last after "normal" permission checks so we

 *            get BSD style process accounting right.

 *            Occurs in several places in the IPC code.

 *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>

 * Nov 1999 - ipc helper functions, unified SMP locking

 *	      Manfred Spraul <manfred@colorfullife.com>

 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().

 *            Mingming Cao <cmm@us.ibm.com>

 * Mar 2006 - support for audit of ipc object properties

 *            Dustin Kirkland <dustin.kirkland@us.ibm.com>

 * Jun 2006 - namespaces ssupport

 *            OpenVZ, SWsoft Inc.

 *            Pavel Emelianov <xemul@openvz.org>

 *

 * General sysv ipc locking scheme:

 *	rcu_read_lock()

 *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr

 *	    tree.

 *	    - perform initial checks (capabilities, auditing and permission,

 *	      etc).

 *	    - perform read-only operations, such as INFO command, that

 *	      do not demand atomicity

 *	      acquire the ipc lock (kern_ipc_perm.lock) through

 *	      ipc_lock_object()

 *		- perform read-only operations that demand atomicity,

 *		  such as STAT command.

 *		- perform data updates, such as SET, RMID commands and

 *		  mechanism-specific operations (semop/semtimedop,

 *		  msgsnd/msgrcv, shmat/shmdt).

 *	    drop the ipc lock, through ipc_unlock_object().

 *	rcu_read_unlock()

 *

 *  The ids->rwsem must be taken when:

 *	- creating, removing and iterating the existing entries in ipc

 *	  identifier sets.

 *	- iterating through files under /proc/sysvipc/

 *

 *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -

 *  see sem_lock().

 */

#include <linux/mm.h>

#include <linux/shm.h>

#include <linux/init.h>

#include <linux/msg.h>

#include <linux/vmalloc.h>

#include <linux/slab.h>

#include <linux/notifier.h>

#include <linux/capability.h>

#include <linux/highuid.h>

#include <linux/security.h>

#include <linux/rcupdate.h>

#include <linux/workqueue.h>

#include <linux/seq_file.h>

#include <linux/proc_fs.h>

#include <linux/audit.h>

#include <linux/nsproxy.h>

#include <linux/rwsem.h>

#include <linux/memory.h>

#include <linux/ipc_namespace.h>

#include <linux/rhashtable.h>

#include <asm/unistd.h>

#include "util.h"

struct ipc_proc_iface {

	const char *path;

	const char *header;

	int ids;

	int (*show)(struct seq_file *, void *);

};

/**

 * ipc_init - initialise ipc subsystem

 *

 * The various sysv ipc resources (semaphores, messages and shared

 * memory) are initialised.

 *

 * A callback routine is registered into the memory hotplug notifier

 * chain: since msgmni scales to lowmem this callback routine will be

 * called upon successful memory add / remove to recompute msmgni.

 */

static int __init ipc_init(void)

{

	proc_mkdir("sysvipc", NULL);

	sem_init();

	msg_init();

	shm_init();

	return 0;

}

device_initcall(ipc_init);

static const struct rhashtable_params ipc_kht_params = {

	.head_offset		= offsetof(struct kern_ipc_perm, khtnode),

	.key_offset		= offsetof(struct kern_ipc_perm, key),

	.key_len		= FIELD_SIZEOF(struct kern_ipc_perm, key),

	.locks_mul		= 1,

	.automatic_shrinking	= true,

};

/**

 * ipc_init_ids	- initialise ipc identifiers

 * @ids: ipc identifier set

 *

 * Set up the sequence range to use for the ipc identifier range (limited

 * below ipc_mni) then initialise the keys hashtable and ids idr.

 */

void ipc_init_ids(struct ipc_ids *ids)

{

	ids->in_use = 0;

	ids->seq = 0;

	init_rwsem(&ids->rwsem);

	rhashtable_init(&ids->key_ht, &ipc_kht_params);

	idr_init(&ids->ipcs_idr);

	ids->max_idx = -1;

	ids->last_idx = -1;

#ifdef CONFIG_CHECKPOINT_RESTORE

	ids->next_id = -1;

#endif

}

#ifdef CONFIG_PROC_FS

static const struct file_operations sysvipc_proc_fops;

/**

 * ipc_init_proc_interface -  create a proc interface for sysipc types using a seq_file interface.

 * @path: Path in procfs

 * @header: Banner to be printed at the beginning of the file.

 * @ids: ipc id table to iterate.

 * @show: show routine.

 */

void __init ipc_init_proc_interface(const char *path, const char *header,

		int ids, int (*show)(struct seq_file *, void *))

{

	struct proc_dir_entry *pde;

	struct ipc_proc_iface *iface;

	iface = kmalloc(sizeof(*iface), GFP_KERNEL);

	if (!iface)

		return;

	iface->path	= path;

	iface->header	= header;

	iface->ids	= ids;

	iface->show	= show;

	pde = proc_create_data(path,

			       S_IRUGO,        /* world readable */

			       NULL,           /* parent dir */

			       &sysvipc_proc_fops,

			       iface);

	if (!pde)

		kfree(iface);

}

#endif

/**

 * ipc_findkey	- find a key in an ipc identifier set

 * @ids: ipc identifier set

 * @key: key to find

 *

 * Returns the locked pointer to the ipc structure if found or NULL

 * otherwise. If key is found ipc points to the owning ipc structure

 *

 * Called with writer ipc_ids.rwsem held.

 */

static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)

{

	struct kern_ipc_perm *ipcp;

	ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,

					      ipc_kht_params);

	if (!ipcp)

		return NULL;

	rcu_read_lock();

	ipc_lock_object(ipcp);

	return ipcp;

}

/*

 * Insert new IPC object into idr tree, and set sequence number and id

 * in the correct order.

 * Especially:

 * - the sequence number must be set before inserting the object into the idr,

 *   because the sequence number is accessed without a lock.

 * - the id can/must be set after inserting the object into the idr.

 *   All accesses must be done after getting kern_ipc_perm.lock.

 *

 * The caller must own kern_ipc_perm.lock.of the new object.

 * On error, the function returns a (negative) error code.

 *

 * To conserve sequence number space, especially with extended ipc_mni,

 * the sequence number is incremented only when the returned ID is less than

 * the last one.

 */

static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)

{

	int idx, next_id = -1;

#ifdef CONFIG_CHECKPOINT_RESTORE

	next_id = ids->next_id;

	ids->next_id = -1;

#endif

	/*

	 * As soon as a new object is inserted into the idr,

	 * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it,

	 * and the lockless preparations for ipc operations can start.

	 * This means especially: permission checks, audit calls, allocation

	 * of undo structures, ...

	 *

	 * Thus the object must be fully initialized, and if something fails,

	 * then the full tear-down sequence must be followed.

	 * (i.e.: set new->deleted, reduce refcount, call_rcu())

	 */

	if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */

		int max_idx;

		max_idx = max(ids->in_use*3/2, ipc_min_cycle);

		max_idx = min(max_idx, ipc_mni);

		/* allocate the idx, with a NULL struct kern_ipc_perm */

		idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx,

					GFP_NOWAIT);

		if (idx >= 0) {

			/*

			 * idx got allocated successfully.

			 * Now calculate the sequence number and set the

			 * pointer for real.

			 */

			if (idx <= ids->last_idx) {

				ids->seq++;

				if (ids->seq >= ipcid_seq_max())

					ids->seq = 0;

			}

			ids->last_idx = idx;

			new->seq = ids->seq;

			/* no need for smp_wmb(), this is done

			 * inside idr_replace, as part of

			 * rcu_assign_pointer

			 */

			idr_replace(&ids->ipcs_idr, new, idx);

		}

	} else {

		new->seq = ipcid_to_seqx(next_id);

		idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),

				0, GFP_NOWAIT);

	}

	if (idx >= 0)

		new->id = (new->seq << ipcmni_seq_shift()) + idx;

	return idx;

}

/**

 * ipc_addid - add an ipc identifier

 * @ids: ipc identifier set

 * @new: new ipc permission set

 * @limit: limit for the number of used ids

 *

 * Add an entry 'new' to the ipc ids idr. The permissions object is

 * initialised and the first free entry is set up and the index assigned

 * is returned. The 'new' entry is returned in a locked state on success.

 *

 * On failure the entry is not locked and a negative err-code is returned.

 * The caller must use ipc_rcu_putref() to free the identifier.

 *

 * Called with writer ipc_ids.rwsem held.

 */

int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)

{

	kuid_t euid;

	kgid_t egid;

	int idx, err;

	/* 1) Initialize the refcount so that ipc_rcu_putref works */

	refcount_set(&new->refcount, 1);

	if (limit > ipc_mni)

		limit = ipc_mni;

	if (ids->in_use >= limit)

		return -ENOSPC;

	idr_preload(GFP_KERNEL);

	spin_lock_init(&new->lock);

	rcu_read_lock();

	spin_lock(&new->lock);

	current_euid_egid(&euid, &egid);

	new->cuid = new->uid = euid;

	new->gid = new->cgid = egid;

	new->deleted = false;

	idx = ipc_idr_alloc(ids, new);

	idr_preload_end();

	if (idx >= 0 && new->key != IPC_PRIVATE) {

		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,

					     ipc_kht_params);

		if (err < 0) {

			idr_remove(&ids->ipcs_idr, idx);

			idx = err;

		}

	}

	if (idx < 0) {

		new->deleted = true;

		spin_unlock(&new->lock);

		rcu_read_unlock();

		return idx;

	}

	ids->in_use++;

	if (idx > ids->max_idx)

		ids->max_idx = idx;

	return idx;

}

/**

 * ipcget_new -	create a new ipc object

 * @ns: ipc namespace

 * @ids: ipc identifier set

 * @ops: the actual creation routine to call

 * @params: its parameters

 *

 * This routine is called by sys_msgget, sys_semget() and sys_shmget()

 * when the key is IPC_PRIVATE.

 */

static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,

		const struct ipc_ops *ops, struct ipc_params *params)

{

	int err;

	down_write(&ids->rwsem);

	err = ops->getnew(ns, params);

	up_write(&ids->rwsem);

	return err;

}

/**

 * ipc_check_perms - check security and permissions for an ipc object

 * @ns: ipc namespace

 * @ipcp: ipc permission set

 * @ops: the actual security routine to call

 * @params: its parameters

 *

 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()

 * when the key is not IPC_PRIVATE and that key already exists in the

 * ds IDR.

 *

 * On success, the ipc id is returned.

 *

 * It is called with ipc_ids.rwsem and ipcp->lock held.

 */

static int ipc_check_perms(struct ipc_namespace *ns,

			   struct kern_ipc_perm *ipcp,

			   const struct ipc_ops *ops,

			   struct ipc_params *params)

{

	int err;

	if (ipcperms(ns, ipcp, params->flg))

		err = -EACCES;

	else {

		err = ops->associate(ipcp, params->flg);

		if (!err)

			err = ipcp->id;

	}

	return err;

}

/**

 * ipcget_public - get an ipc object or create a new one

 * @ns: ipc namespace

 * @ids: ipc identifier set

 * @ops: the actual creation routine to call

 * @params: its parameters

 *

 * This routine is called by sys_msgget, sys_semget() and sys_shmget()

 * when the key is not IPC_PRIVATE.

 * It adds a new entry if the key is not found and does some permission

 * / security checkings if the key is found.

 *

 * On success, the ipc id is returned.

 */

static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,

		const struct ipc_ops *ops, struct ipc_params *params)

{

	struct kern_ipc_perm *ipcp;

	int flg = params->flg;

	int err;

	/*

	 * Take the lock as a writer since we are potentially going to add

	 * a new entry + read locks are not "upgradable"

	 */

	down_write(&ids->rwsem);

	ipcp = ipc_findkey(ids, params->key);

	if (ipcp == NULL) {

		/* key not used */

		if (!(flg & IPC_CREAT))

			err = -ENOENT;

		else

			err = ops->getnew(ns, params);

	} else {

		/* ipc object has been locked by ipc_findkey() */

		if (flg & IPC_CREAT && flg & IPC_EXCL)

			err = -EEXIST;

		else {

			err = 0;

			if (ops->more_checks)

				err = ops->more_checks(ipcp, params);

			if (!err)

				/*

				 * ipc_check_perms returns the IPC id on

				 * success

				 */

				err = ipc_check_perms(ns, ipcp, ops, params);

		}

		ipc_unlock(ipcp);

	}

	up_write(&ids->rwsem);

	return err;

}

/**

 * ipc_kht_remove - remove an ipc from the key hashtable

 * @ids: ipc identifier set

 * @ipcp: ipc perm structure containing the key to remove

 *

 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held

 * before this function is called, and remain locked on the exit.

 */

static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)

{

	if (ipcp->key != IPC_PRIVATE)

		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,

				       ipc_kht_params);

}

/**

 * ipc_rmid - remove an ipc identifier

 * @ids: ipc identifier set

 * @ipcp: ipc perm structure containing the identifier to remove

 *

 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held

 * before this function is called, and remain locked on the exit.

 */

void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)

{

	int idx = ipcid_to_idx(ipcp->id);

	idr_remove(&ids->ipcs_idr, idx);

	ipc_kht_remove(ids, ipcp);

	ids->in_use--;

	ipcp->deleted = true;

	if (unlikely(idx == ids->max_idx)) {

		do {

			idx--;

			if (idx == -1)

				break;

		} while (!idr_find(&ids->ipcs_idr, idx));

		ids->max_idx = idx;

	}

}

/**

 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE

 * @ids: ipc identifier set

 * @ipcp: ipc perm structure containing the key to modify

 *

 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held

 * before this function is called, and remain locked on the exit.

 */

void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)

{

	ipc_kht_remove(ids, ipcp);

	ipcp->key = IPC_PRIVATE;

}

bool ipc_rcu_getref(struct kern_ipc_perm *ptr)

{

	return refcount_inc_not_zero(&ptr->refcount);

}

void ipc_rcu_putref(struct kern_ipc_perm *ptr,

			void (*func)(struct rcu_head *head))

{

	if (!refcount_dec_and_test(&ptr->refcount))

		return;

	call_rcu(&ptr->rcu, func);

}

/**

 * ipcperms - check ipc permissions

 * @ns: ipc namespace

 * @ipcp: ipc permission set

 * @flag: desired permission set

 *

 * Check user, group, other permissions for access

 * to ipc resources. return 0 if allowed

 *

 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>

 */

int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)

{

	kuid_t euid = current_euid();

	int requested_mode, granted_mode;

	audit_ipc_obj(ipcp);

	requested_mode = (flag >> 6) | (flag >> 3) | flag;

	granted_mode = ipcp->mode;

	if (uid_eq(euid, ipcp->cuid) ||

	    uid_eq(euid, ipcp->uid))

		granted_mode >>= 6;

	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))

		granted_mode >>= 3;

	/* is there some bit set in requested_mode but not in granted_mode? */

	if ((requested_mode & ~granted_mode & 0007) &&

	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))

		return -1;

	return security_ipc_permission(ipcp, flag);

}

/*

 * Functions to convert between the kern_ipc_perm structure and the

 * old/new ipc_perm structures

 */

/**

 * kernel_to_ipc64_perm	- convert kernel ipc permissions to user

 * @in: kernel permissions

 * @out: new style ipc permissions

 *

 * Turn the kernel object @in into a set of permissions descriptions

 * for returning to userspace (@out).

 */

void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)

{

	out->key	= in->key;

	out->uid	= from_kuid_munged(current_user_ns(), in->uid);

	out->gid	= from_kgid_munged(current_user_ns(), in->gid);

	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);

	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);

	out->mode	= in->mode;

	out->seq	= in->seq;

}

/**

 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old

 * @in: new style ipc permissions

 * @out: old style ipc permissions

 *

 * Turn the new style permissions object @in into a compatibility

 * object and store it into the @out pointer.

 */

void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)

{

	out->key	= in->key;

	SET_UID(out->uid, in->uid);

	SET_GID(out->gid, in->gid);

	SET_UID(out->cuid, in->cuid);

	SET_GID(out->cgid, in->cgid);

	out->mode	= in->mode;

	out->seq	= in->seq;

}

/**

 * ipc_obtain_object_idr

 * @ids: ipc identifier set

 * @id: ipc id to look for

 *

 * Look for an id in the ipc ids idr and return associated ipc object.

 *

 * Call inside the RCU critical section.

 * The ipc object is *not* locked on exit.

 */

struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)

{

	struct kern_ipc_perm *out;

	int idx = ipcid_to_idx(id);

	out = idr_find(&ids->ipcs_idr, idx);

	if (!out)

		return ERR_PTR(-EINVAL);

	return out;

}

/**

 * ipc_obtain_object_check

 * @ids: ipc identifier set

 * @id: ipc id to look for

 *

 * Similar to ipc_obtain_object_idr() but also checks the ipc object

 * sequence number.

 *

 * Call inside the RCU critical section.

 * The ipc object is *not* locked on exit.

 */

struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)

{

	struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);

	if (IS_ERR(out))

		goto out;

	if (ipc_checkid(out, id))

		return ERR_PTR(-EINVAL);

out:

	return out;

}

/**

 * ipcget - Common sys_*get() code

 * @ns: namespace

 * @ids: ipc identifier set

 * @ops: operations to be called on ipc object creation, permission checks

 *       and further checks

 * @params: the parameters needed by the previous operations.

 *

 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().

 */

int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,

			const struct ipc_ops *ops, struct ipc_params *params)

{

	if (params->key == IPC_PRIVATE)

		return ipcget_new(ns, ids, ops, params);

	else

		return ipcget_public(ns, ids, ops, params);

}

/**

 * ipc_update_perm - update the permissions of an ipc object

 * @in:  the permission given as input.

 * @out: the permission of the ipc to set.

 */

int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)

{

	kuid_t uid = make_kuid(current_user_ns(), in->uid);

	kgid_t gid = make_kgid(current_user_ns(), in->gid);

	if (!uid_valid(uid) || !gid_valid(gid))

		return -EINVAL;

	out->uid = uid;

	out->gid = gid;

	out->mode = (out->mode & ~S_IRWXUGO)

		| (in->mode & S_IRWXUGO);

	return 0;

}

/**

 * ipcctl_obtain_check - retrieve an ipc object and check permissions

 * @ns:  ipc namespace

 * @ids:  the table of ids where to look for the ipc

 * @id:   the id of the ipc to retrieve

 * @cmd:  the cmd to check

 * @perm: the permission to set

 * @extra_perm: one extra permission parameter used by msq

 *

 * This function does some common audit and permissions check for some IPC_XXX

 * cmd and is called from semctl_down, shmctl_down and msgctl_down.

 *

 * It:

 *   - retrieves the ipc object with the given id in the given table.

 *   - performs some audit and permission check, depending on the given cmd

 *   - returns a pointer to the ipc object or otherwise, the corresponding

 *     error.

 *

 * Call holding the both the rwsem and the rcu read lock.

 */

struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,

					struct ipc_ids *ids, int id, int cmd,

					struct ipc64_perm *perm, int extra_perm)

{

	kuid_t euid;

	int err = -EPERM;

	struct kern_ipc_perm *ipcp;

	ipcp = ipc_obtain_object_check(ids, id);

	if (IS_ERR(ipcp)) {

		err = PTR_ERR(ipcp);

		goto err;

	}

	audit_ipc_obj(ipcp);

	if (cmd == IPC_SET)

		audit_ipc_set_perm(extra_perm, perm->uid,

				   perm->gid, perm->mode);

	euid = current_euid();

	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||

	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))

		return ipcp; /* successful lookup */

err:

	return ERR_PTR(err);

}

#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION

/**

 * ipc_parse_version - ipc call version