[linux-block.git] / mm / memfd.c

/*
 * memfd_create system call and file sealing support
 *
 * Code was originally included in shmem.c, and broken out to facilitate
 * use by hugetlbfs as well as tmpfs.
 *
 * This file is released under the GPL.
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/sched/signal.h>
#include <linux/khugepaged.h>
#include <linux/syscalls.h>
#include <linux/hugetlb.h>
#include <linux/shmem_fs.h>
#include <linux/memfd.h>
#include <linux/pid_namespace.h>
#include <uapi/linux/memfd.h>

/*
 * We need a tag: a new tag would expand every xa_node by 8 bytes,
 * so reuse a tag which we firmly believe is never set or cleared on tmpfs
 * or hugetlbfs because they are memory only filesystems.
 */
#define MEMFD_TAG_PINNED        PAGECACHE_TAG_TOWRITE
#define LAST_SCAN               4       /* about 150ms max */

static bool memfd_folio_has_extra_refs(struct folio *folio)
{
	return folio_ref_count(folio) - folio_mapcount(folio) !=
	       folio_nr_pages(folio);
}

static void memfd_tag_pins(struct xa_state *xas)
{
	struct folio *folio;
	int latency = 0;

	lru_add_drain();

	xas_lock_irq(xas);
	xas_for_each(xas, folio, ULONG_MAX) {
		if (!xa_is_value(folio) && memfd_folio_has_extra_refs(folio))
			xas_set_mark(xas, MEMFD_TAG_PINNED);

		if (++latency < XA_CHECK_SCHED)
			continue;
		latency = 0;

		xas_pause(xas);
		xas_unlock_irq(xas);
		cond_resched();
		xas_lock_irq(xas);
	}
	xas_unlock_irq(xas);
}

/*
 * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
 * via get_user_pages(), drivers might have some pending I/O without any active
 * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all folios
 * and see whether it has an elevated ref-count. If so, we tag them and wait for
 * them to be dropped.
 * The caller must guarantee that no new user will acquire writable references
 * to those folios to avoid races.
 */
static int memfd_wait_for_pins(struct address_space *mapping)
{
	XA_STATE(xas, &mapping->i_pages, 0);
	struct folio *folio;
	int error, scan;

	memfd_tag_pins(&xas);

	error = 0;
	for (scan = 0; scan <= LAST_SCAN; scan++) {
		int latency = 0;

		if (!xas_marked(&xas, MEMFD_TAG_PINNED))
			break;

		if (!scan)
			lru_add_drain_all();
		else if (schedule_timeout_killable((HZ << scan) / 200))
			scan = LAST_SCAN;

		xas_set(&xas, 0);
		xas_lock_irq(&xas);
		xas_for_each_marked(&xas, folio, ULONG_MAX, MEMFD_TAG_PINNED) {
			bool clear = true;

			if (!xa_is_value(folio) &&
			    memfd_folio_has_extra_refs(folio)) {
				/*
				 * On the last scan, we clean up all those tags
				 * we inserted; but make a note that we still
				 * found folios pinned.
				 */
				if (scan == LAST_SCAN)
					error = -EBUSY;
				else
					clear = false;
			}
			if (clear)
				xas_clear_mark(&xas, MEMFD_TAG_PINNED);

			if (++latency < XA_CHECK_SCHED)
				continue;
			latency = 0;

			xas_pause(&xas);
			xas_unlock_irq(&xas);
			cond_resched();
			xas_lock_irq(&xas);
		}
		xas_unlock_irq(&xas);
	}

	return error;
}

static unsigned int *memfd_file_seals_ptr(struct file *file)
{
	if (shmem_file(file))
		return &SHMEM_I(file_inode(file))->seals;

#ifdef CONFIG_HUGETLBFS
	if (is_file_hugepages(file))
		return &HUGETLBFS_I(file_inode(file))->seals;
#endif

	return NULL;
}

#define F_ALL_SEALS (F_SEAL_SEAL | \
		     F_SEAL_EXEC | \
		     F_SEAL_SHRINK | \
		     F_SEAL_GROW | \
		     F_SEAL_WRITE | \
		     F_SEAL_FUTURE_WRITE)

static int memfd_add_seals(struct file *file, unsigned int seals)
{
	struct inode *inode = file_inode(file);
	unsigned int *file_seals;
	int error;

	/*
	 * SEALING
	 * Sealing allows multiple parties to share a tmpfs or hugetlbfs file
	 * but restrict access to a specific subset of file operations. Seals
	 * can only be added, but never removed. This way, mutually untrusted
	 * parties can share common memory regions with a well-defined policy.
	 * A malicious peer can thus never perform unwanted operations on a
	 * shared object.
	 *
	 * Seals are only supported on special tmpfs or hugetlbfs files and
	 * always affect the whole underlying inode. Once a seal is set, it
	 * may prevent some kinds of access to the file. Currently, the
	 * following seals are defined:
	 *   SEAL_SEAL: Prevent further seals from being set on this file
	 *   SEAL_SHRINK: Prevent the file from shrinking
	 *   SEAL_GROW: Prevent the file from growing
	 *   SEAL_WRITE: Prevent write access to the file
	 *   SEAL_EXEC: Prevent modification of the exec bits in the file mode
	 *
	 * As we don't require any trust relationship between two parties, we
	 * must prevent seals from being removed. Therefore, sealing a file
	 * only adds a given set of seals to the file, it never touches
	 * existing seals. Furthermore, the "setting seals"-operation can be
	 * sealed itself, which basically prevents any further seal from being
	 * added.
	 *
	 * Semantics of sealing are only defined on volatile files. Only
	 * anonymous tmpfs and hugetlbfs files support sealing. More
	 * importantly, seals are never written to disk. Therefore, there's
	 * no plan to support it on other file types.
	 */

	if (!(file->f_mode & FMODE_WRITE))
		return -EPERM;
	if (seals & ~(unsigned int)F_ALL_SEALS)
		return -EINVAL;

	inode_lock(inode);

	file_seals = memfd_file_seals_ptr(file);
	if (!file_seals) {
		error = -EINVAL;
		goto unlock;
	}

	if (*file_seals & F_SEAL_SEAL) {
		error = -EPERM;
		goto unlock;
	}

	if ((seals & F_SEAL_WRITE) && !(*file_seals & F_SEAL_WRITE)) {
		error = mapping_deny_writable(file->f_mapping);
		if (error)
			goto unlock;

		error = memfd_wait_for_pins(file->f_mapping);
		if (error) {
			mapping_allow_writable(file->f_mapping);
			goto unlock;
		}
	}

	/*
	 * SEAL_EXEC implys SEAL_WRITE, making W^X from the start.
	 */
	if (seals & F_SEAL_EXEC && inode->i_mode & 0111)
		seals |= F_SEAL_SHRINK|F_SEAL_GROW|F_SEAL_WRITE|F_SEAL_FUTURE_WRITE;

	*file_seals |= seals;
	error = 0;

unlock:
	inode_unlock(inode);
	return error;
}

static int memfd_get_seals(struct file *file)
{
	unsigned int *seals = memfd_file_seals_ptr(file);

	return seals ? *seals : -EINVAL;
}

long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
{
	long error;

	switch (cmd) {
	case F_ADD_SEALS:
		error = memfd_add_seals(file, arg);
		break;
	case F_GET_SEALS:
		error = memfd_get_seals(file);
		break;
	default:
		error = -EINVAL;
		break;
	}

	return error;
}

#define MFD_NAME_PREFIX "memfd:"
#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)

#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)

static int check_sysctl_memfd_noexec(unsigned int *flags)
{
#ifdef CONFIG_SYSCTL
	struct pid_namespace *ns = task_active_pid_ns(current);
	int sysctl = pidns_memfd_noexec_scope(ns);

	if (!(*flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) {
		if (sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL)
			*flags |= MFD_NOEXEC_SEAL;
		else
			*flags |= MFD_EXEC;
	}

	if (!(*flags & MFD_NOEXEC_SEAL) && sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED) {
		pr_err_ratelimited(
			"%s[%d]: memfd_create() requires MFD_NOEXEC_SEAL with vm.memfd_noexec=%d\n",
			current->comm, task_pid_nr(current), sysctl);
		return -EACCES;
	}
#endif
	return 0;
}

SYSCALL_DEFINE2(memfd_create,
		const char __user *, uname,
		unsigned int, flags)
{
	unsigned int *file_seals;
	struct file *file;
	int fd, error;
	char *name;
	long len;

	if (!(flags & MFD_HUGETLB)) {
		if (flags & ~(unsigned int)MFD_ALL_FLAGS)
			return -EINVAL;
	} else {
		/* Allow huge page size encoding in flags. */
		if (flags & ~(unsigned int)(MFD_ALL_FLAGS |
				(MFD_HUGE_MASK << MFD_HUGE_SHIFT)))
			return -EINVAL;
	}

	/* Invalid if both EXEC and NOEXEC_SEAL are set.*/
	if ((flags & MFD_EXEC) && (flags & MFD_NOEXEC_SEAL))
		return -EINVAL;

	error = check_sysctl_memfd_noexec(&flags);
	if (error < 0)
		return error;

	/* length includes terminating zero */
	len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
	if (len <= 0)
		return -EFAULT;
	if (len > MFD_NAME_MAX_LEN + 1)
		return -EINVAL;

	name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_KERNEL);
	if (!name)
		return -ENOMEM;

	strcpy(name, MFD_NAME_PREFIX);
	if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
		error = -EFAULT;
		goto err_name;
	}

	/* terminating-zero may have changed after strnlen_user() returned */
	if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
		error = -EFAULT;
		goto err_name;
	}

	fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
	if (fd < 0) {
		error = fd;
		goto err_name;
	}

	if (flags & MFD_HUGETLB) {
		file = hugetlb_file_setup(name, 0, VM_NORESERVE,
					HUGETLB_ANONHUGE_INODE,
					(flags >> MFD_HUGE_SHIFT) &
					MFD_HUGE_MASK);
	} else
		file = shmem_file_setup(name, 0, VM_NORESERVE);
	if (IS_ERR(file)) {
		error = PTR_ERR(file);
		goto err_fd;
	}
	file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
	file->f_flags |= O_LARGEFILE;

	if (flags & MFD_NOEXEC_SEAL) {
		struct inode *inode = file_inode(file);

		inode->i_mode &= ~0111;
		file_seals = memfd_file_seals_ptr(file);
		if (file_seals) {
			*file_seals &= ~F_SEAL_SEAL;
			*file_seals |= F_SEAL_EXEC;
		}
	} else if (flags & MFD_ALLOW_SEALING) {
		/* MFD_EXEC and MFD_ALLOW_SEALING are set */
		file_seals = memfd_file_seals_ptr(file);
		if (file_seals)
			*file_seals &= ~F_SEAL_SEAL;
	}

	fd_install(fd, file);
	kfree(name);
	return fd;

err_fd:
	put_unused_fd(fd);
err_name:
	kfree(name);
	return error;
}
Commit	Line	Data
5d752600 MK	1	/*
	2	* memfd_create system call and file sealing support
	3	*
	4	* Code was originally included in shmem.c, and broken out to facilitate
	5	* use by hugetlbfs as well as tmpfs.
	6	*
	7	* This file is released under the GPL.
	8	*/
	9
	10	#include <linux/fs.h>
	11	#include <linux/vfs.h>
	12	#include <linux/pagemap.h>
	13	#include <linux/file.h>
	14	#include <linux/mm.h>
	15	#include <linux/sched/signal.h>
	16	#include <linux/khugepaged.h>
	17	#include <linux/syscalls.h>
	18	#include <linux/hugetlb.h>
	19	#include <linux/shmem_fs.h>
	20	#include <linux/memfd.h>
105ff533	21	#include <linux/pid_namespace.h>
5d752600 MK	22	#include <uapi/linux/memfd.h>
	23
	24	/*
2313216f	25	* We need a tag: a new tag would expand every xa_node by 8 bytes,
5d752600 MK	26	* so reuse a tag which we firmly believe is never set or cleared on tmpfs
	27	* or hugetlbfs because they are memory only filesystems.
	28	*/
	29	#define MEMFD_TAG_PINNED PAGECACHE_TAG_TOWRITE
	30	#define LAST_SCAN 4 /* about 150ms max */
	31
b4d02baa DH	32	static bool memfd_folio_has_extra_refs(struct folio *folio)
	33	{
	34	return folio_ref_count(folio) - folio_mapcount(folio) !=
	35	folio_nr_pages(folio);
	36	}
	37
ef3038a5	38	static void memfd_tag_pins(struct xa_state *xas)
5d752600	39	{
b4d02baa	40	struct folio *folio;
f2b277c4	41	int latency = 0;
5d752600 MK	42
5d752600 MK	43	lru_add_drain();
5d752600	44
ef3038a5	45	xas_lock_irq(xas);
b4d02baa DH	46	xas_for_each(xas, folio, ULONG_MAX) {
b4d02baa DH	47	if (!xa_is_value(folio) && memfd_folio_has_extra_refs(folio))
ef3038a5	48	xas_set_mark(xas, MEMFD_TAG_PINNED);
5d752600	49
b4d02baa	50	if (++latency < XA_CHECK_SCHED)
ef3038a5	51	continue;
f2b277c4	52	latency = 0;
ef3038a5 MW	53
	54	xas_pause(xas);
	55	xas_unlock_irq(xas);
	56	cond_resched();
	57	xas_lock_irq(xas);
5d752600	58	}
ef3038a5	59	xas_unlock_irq(xas);
5d752600 MK	60	}
	61
	62	/*
	63	* Setting SEAL_WRITE requires us to verify there's no pending writer. However,
	64	* via get_user_pages(), drivers might have some pending I/O without any active
b4d02baa	65	* user-space mappings (eg., direct-IO, AIO). Therefore, we look at all folios
5d752600 MK	66	* and see whether it has an elevated ref-count. If so, we tag them and wait for
	67	* them to be dropped.
	68	* The caller must guarantee that no new user will acquire writable references
b4d02baa	69	* to those folios to avoid races.
5d752600 MK	70	*/
	71	static int memfd_wait_for_pins(struct address_space *mapping)
	72	{
2313216f	73	XA_STATE(xas, &mapping->i_pages, 0);
b4d02baa	74	struct folio *folio;
5d752600 MK	75	int error, scan;
5d752600 MK	76
ef3038a5	77	memfd_tag_pins(&xas);
5d752600 MK	78
	79	error = 0;
	80	for (scan = 0; scan <= LAST_SCAN; scan++) {
f2b277c4	81	int latency = 0;
2313216f MW	82
2313216f MW	83	if (!xas_marked(&xas, MEMFD_TAG_PINNED))
5d752600 MK	84	break;
	85
	86	if (!scan)
	87	lru_add_drain_all();
	88	else if (schedule_timeout_killable((HZ << scan) / 200))
	89	scan = LAST_SCAN;
	90
2313216f MW	91	xas_set(&xas, 0);
2313216f MW	92	xas_lock_irq(&xas);
b4d02baa	93	xas_for_each_marked(&xas, folio, ULONG_MAX, MEMFD_TAG_PINNED) {
2313216f	94	bool clear = true;
f2b277c4	95
b4d02baa DH	96	if (!xa_is_value(folio) &&
b4d02baa DH	97	memfd_folio_has_extra_refs(folio)) {
5d752600 MK	98	/*
	99	* On the last scan, we clean up all those tags
	100	* we inserted; but make a note that we still
b4d02baa	101	* found folios pinned.
5d752600	102	*/
2313216f MW	103	if (scan == LAST_SCAN)
	104	error = -EBUSY;
	105	else
	106	clear = false;
5d752600	107	}
2313216f MW	108	if (clear)
2313216f MW	109	xas_clear_mark(&xas, MEMFD_TAG_PINNED);
f2b277c4	110
b4d02baa	111	if (++latency < XA_CHECK_SCHED)
2313216f	112	continue;
f2b277c4	113	latency = 0;
5d752600	114
2313216f MW	115	xas_pause(&xas);
	116	xas_unlock_irq(&xas);
	117	cond_resched();
	118	xas_lock_irq(&xas);
5d752600	119	}
2313216f	120	xas_unlock_irq(&xas);
5d752600 MK	121	}
	122
	123	return error;
	124	}
	125
	126	static unsigned int memfd_file_seals_ptr(struct file file)
	127	{
	128	if (shmem_file(file))
	129	return &SHMEM_I(file_inode(file))->seals;
	130
	131	#ifdef CONFIG_HUGETLBFS
	132	if (is_file_hugepages(file))
	133	return &HUGETLBFS_I(file_inode(file))->seals;
	134	#endif
	135
	136	return NULL;
	137	}
	138
	139	#define F_ALL_SEALS (F_SEAL_SEAL \| \
6fd73538	140	F_SEAL_EXEC \| \
5d752600 MK	141	F_SEAL_SHRINK \| \
5d752600 MK	142	F_SEAL_GROW \| \
ab3948f5 JFG	143	F_SEAL_WRITE \| \
ab3948f5 JFG	144	F_SEAL_FUTURE_WRITE)
5d752600 MK	145
	146	static int memfd_add_seals(struct file *file, unsigned int seals)
	147	{
	148	struct inode *inode = file_inode(file);
	149	unsigned int *file_seals;
	150	int error;
	151
	152	/*
	153	* SEALING
	154	* Sealing allows multiple parties to share a tmpfs or hugetlbfs file
	155	* but restrict access to a specific subset of file operations. Seals
	156	* can only be added, but never removed. This way, mutually untrusted
	157	* parties can share common memory regions with a well-defined policy.
	158	* A malicious peer can thus never perform unwanted operations on a
	159	* shared object.
	160	*
	161	* Seals are only supported on special tmpfs or hugetlbfs files and
	162	* always affect the whole underlying inode. Once a seal is set, it
	163	* may prevent some kinds of access to the file. Currently, the
	164	* following seals are defined:
	165	* SEAL_SEAL: Prevent further seals from being set on this file
	166	* SEAL_SHRINK: Prevent the file from shrinking
	167	* SEAL_GROW: Prevent the file from growing
	168	* SEAL_WRITE: Prevent write access to the file
6fd73538	169	* SEAL_EXEC: Prevent modification of the exec bits in the file mode
5d752600 MK	170	*
	171	* As we don't require any trust relationship between two parties, we
	172	* must prevent seals from being removed. Therefore, sealing a file
	173	* only adds a given set of seals to the file, it never touches
	174	* existing seals. Furthermore, the "setting seals"-operation can be
	175	* sealed itself, which basically prevents any further seal from being
	176	* added.
	177	*
	178	* Semantics of sealing are only defined on volatile files. Only
	179	* anonymous tmpfs and hugetlbfs files support sealing. More
	180	* importantly, seals are never written to disk. Therefore, there's
	181	* no plan to support it on other file types.
	182	*/
	183
	184	if (!(file->f_mode & FMODE_WRITE))
	185	return -EPERM;
	186	if (seals & ~(unsigned int)F_ALL_SEALS)
	187	return -EINVAL;
	188
	189	inode_lock(inode);
	190
	191	file_seals = memfd_file_seals_ptr(file);
	192	if (!file_seals) {
	193	error = -EINVAL;
	194	goto unlock;
	195	}
	196
	197	if (*file_seals & F_SEAL_SEAL) {
	198	error = -EPERM;
	199	goto unlock;
	200	}
	201
	202	if ((seals & F_SEAL_WRITE) && !(*file_seals & F_SEAL_WRITE)) {
	203	error = mapping_deny_writable(file->f_mapping);
	204	if (error)
	205	goto unlock;
	206
	207	error = memfd_wait_for_pins(file->f_mapping);
	208	if (error) {
	209	mapping_allow_writable(file->f_mapping);
	210	goto unlock;
	211	}
	212	}
	213
c4f75bc8 JX	214	/*
	215	* SEAL_EXEC implys SEAL_WRITE, making W^X from the start.
	216	*/
	217	if (seals & F_SEAL_EXEC && inode->i_mode & 0111)
	218	seals \|= F_SEAL_SHRINK\|F_SEAL_GROW\|F_SEAL_WRITE\|F_SEAL_FUTURE_WRITE;
	219
5d752600 MK	220	*file_seals \|= seals;
	221	error = 0;
	222
	223	unlock:
	224	inode_unlock(inode);
	225	return error;
	226	}
	227
	228	static int memfd_get_seals(struct file *file)
	229	{
	230	unsigned int *seals = memfd_file_seals_ptr(file);
	231
	232	return seals ? *seals : -EINVAL;
	233	}
	234
f7b8f70b	235	long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
5d752600 MK	236	{
	237	long error;
	238
	239	switch (cmd) {
	240	case F_ADD_SEALS:
5d752600 MK	241	error = memfd_add_seals(file, arg);
	242	break;
	243	case F_GET_SEALS:
	244	error = memfd_get_seals(file);
	245	break;
	246	default:
	247	error = -EINVAL;
	248	break;
	249	}
	250
	251	return error;
	252	}
	253
	254	#define MFD_NAME_PREFIX "memfd:"
	255	#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
	256	#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
	257
105ff533	258	#define MFD_ALL_FLAGS (MFD_CLOEXEC \| MFD_ALLOW_SEALING \| MFD_HUGETLB \| MFD_NOEXEC_SEAL \| MFD_EXEC)
5d752600	259
72de2591 JX	260	static int check_sysctl_memfd_noexec(unsigned int *flags)
	261	{
	262	#ifdef CONFIG_SYSCTL
9876cfe8 AS	263	struct pid_namespace *ns = task_active_pid_ns(current);
9876cfe8 AS	264	int sysctl = pidns_memfd_noexec_scope(ns);
72de2591 JX	265
72de2591 JX	266	if (!(*flags & (MFD_EXEC \| MFD_NOEXEC_SEAL))) {
202e1422	267	if (sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL)
72de2591 JX	268	*flags \|= MFD_NOEXEC_SEAL;
	269	else
	270	*flags \|= MFD_EXEC;
	271	}
	272
202e1422 AS	273	if (!(*flags & MFD_NOEXEC_SEAL) && sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED) {
	274	pr_err_ratelimited(
	275	"%s[%d]: memfd_create() requires MFD_NOEXEC_SEAL with vm.memfd_noexec=%d\n",
	276	current->comm, task_pid_nr(current), sysctl);
72de2591 JX	277	return -EACCES;
	278	}
	279	#endif
72de2591 JX	280	return 0;
	281	}
	282
5d752600 MK	283	SYSCALL_DEFINE2(memfd_create,
	284	const char __user *, uname,
	285	unsigned int, flags)
	286	{
	287	unsigned int *file_seals;
	288	struct file *file;
	289	int fd, error;
	290	char *name;
	291	long len;
	292
	293	if (!(flags & MFD_HUGETLB)) {
	294	if (flags & ~(unsigned int)MFD_ALL_FLAGS)
	295	return -EINVAL;
	296	} else {
	297	/* Allow huge page size encoding in flags. */
	298	if (flags & ~(unsigned int)(MFD_ALL_FLAGS \|
	299	(MFD_HUGE_MASK << MFD_HUGE_SHIFT)))
	300	return -EINVAL;
	301	}
	302
105ff533 JX	303	/* Invalid if both EXEC and NOEXEC_SEAL are set.*/
	304	if ((flags & MFD_EXEC) && (flags & MFD_NOEXEC_SEAL))
	305	return -EINVAL;
	306
202e1422 AS	307	error = check_sysctl_memfd_noexec(&flags);
	308	if (error < 0)
	309	return error;
72de2591	310
5d752600 MK	311	/* length includes terminating zero */
	312	len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
	313	if (len <= 0)
	314	return -EFAULT;
	315	if (len > MFD_NAME_MAX_LEN + 1)
	316	return -EINVAL;
	317
	318	name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_KERNEL);
	319	if (!name)
	320	return -ENOMEM;
	321
	322	strcpy(name, MFD_NAME_PREFIX);
	323	if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
	324	error = -EFAULT;
	325	goto err_name;
	326	}
	327
	328	/* terminating-zero may have changed after strnlen_user() returned */
	329	if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
	330	error = -EFAULT;
	331	goto err_name;
	332	}
	333
	334	fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
	335	if (fd < 0) {
	336	error = fd;
	337	goto err_name;
	338	}
	339
	340	if (flags & MFD_HUGETLB) {
83c1fd76	341	file = hugetlb_file_setup(name, 0, VM_NORESERVE,
5d752600 MK	342	HUGETLB_ANONHUGE_INODE,
	343	(flags >> MFD_HUGE_SHIFT) &
	344	MFD_HUGE_MASK);
	345	} else
	346	file = shmem_file_setup(name, 0, VM_NORESERVE);
	347	if (IS_ERR(file)) {
	348	error = PTR_ERR(file);
	349	goto err_fd;
	350	}
	351	file->f_mode \|= FMODE_LSEEK \| FMODE_PREAD \| FMODE_PWRITE;
c9c554f2	352	file->f_flags \|= O_LARGEFILE;
5d752600	353
105ff533 JX	354	if (flags & MFD_NOEXEC_SEAL) {
	355	struct inode *inode = file_inode(file);
	356
	357	inode->i_mode &= ~0111;
	358	file_seals = memfd_file_seals_ptr(file);
935d44ac RS	359	if (file_seals) {
	360	*file_seals &= ~F_SEAL_SEAL;
	361	*file_seals \|= F_SEAL_EXEC;
	362	}
105ff533 JX	363	} else if (flags & MFD_ALLOW_SEALING) {
105ff533 JX	364	/* MFD_EXEC and MFD_ALLOW_SEALING are set */
5d752600	365	file_seals = memfd_file_seals_ptr(file);
935d44ac RS	366	if (file_seals)
935d44ac RS	367	*file_seals &= ~F_SEAL_SEAL;
5d752600 MK	368	}
	369
	370	fd_install(fd, file);
	371	kfree(name);
	372	return fd;
	373
	374	err_fd:
	375	put_unused_fd(fd);
	376	err_name:
	377	kfree(name);
	378	return error;
	379	}