Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 344 insertions, 0 deletions

diff --git a/mm/memfd.c b/mm/memfd.c
new file mode 100644
index 000000000..b0104b49b
--- /dev/null
+++ b/mm/memfd.c
@@ -0,0 +1,344 @@
+/*
+ * 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 <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 void memfd_tag_pins(struct xa_state *xas)
+{
+	struct page *page;
+	int latency = 0;
+	int cache_count;
+
+	lru_add_drain();
+
+	xas_lock_irq(xas);
+	xas_for_each(xas, page, ULONG_MAX) {
+		cache_count = 1;
+		if (!xa_is_value(page) &&
+		    PageTransHuge(page) && !PageHuge(page))
+			cache_count = HPAGE_PMD_NR;
+
+		if (!xa_is_value(page) &&
+		    page_count(page) - total_mapcount(page) != cache_count)
+			xas_set_mark(xas, MEMFD_TAG_PINNED);
+		if (cache_count != 1)
+			xas_set(xas, page->index + cache_count);
+
+		latency += cache_count;
+		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 pages
+ * 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 pages to avoid races.
+ */
+static int memfd_wait_for_pins(struct address_space *mapping)
+{
+	XA_STATE(xas, &mapping->i_pages, 0);
+	struct page *page;
+	int error, scan;
+
+	memfd_tag_pins(&xas);
+
+	error = 0;
+	for (scan = 0; scan <= LAST_SCAN; scan++) {
+		int latency = 0;
+		int cache_count;
+
+		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, page, ULONG_MAX, MEMFD_TAG_PINNED) {
+			bool clear = true;
+
+			cache_count = 1;
+			if (!xa_is_value(page) &&
+			    PageTransHuge(page) && !PageHuge(page))
+				cache_count = HPAGE_PMD_NR;
+
+			if (!xa_is_value(page) && cache_count !=
+			    page_count(page) - total_mapcount(page)) {
+				/*
+				 * On the last scan, we clean up all those tags
+				 * we inserted; but make a note that we still
+				 * found pages pinned.
+				 */
+				if (scan == LAST_SCAN)
+					error = -EBUSY;
+				else
+					clear = false;
+			}
+			if (clear)
+				xas_clear_mark(&xas, MEMFD_TAG_PINNED);
+
+			latency += cache_count;
+			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_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
+	 *
+	 * 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;
+		}
+	}
+
+	*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 long arg)
+{
+	long error;
+
+	switch (cmd) {
+	case F_ADD_SEALS:
+		/* disallow upper 32bit */
+		if (arg > UINT_MAX)
+			return -EINVAL;
+
+		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)
+
+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;
+	}
+
+	/* 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_ALLOW_SEALING) {
+		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;
+}