// SPDX-License-Identifier: GPL-2.0-only/* *  linux/fs/file_table.c * *  Copyright (C) 1991, 1992  Linus Torvalds *  Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu) */ #include <linux/string.h>#include <linux/slab.h>#include <linux/file.h>#include <linux/fdtable.h>#include <linux/init.h>#include <linux/module.h>#include <linux/fs.h>#include <linux/security.h>#include <linux/cred.h>#include <linux/eventpoll.h>#include <linux/rcupdate.h>#include <linux/mount.h>#include <linux/capability.h>#include <linux/cdev.h>#include <linux/fsnotify.h>#include <linux/sysctl.h>#include <linux/percpu_counter.h>#include <linux/percpu.h>#include <linux/task_work.h>#include <linux/ima.h>#include <linux/swap.h> #include <linux/atomic.h> #include "internal.h" /* sysctl tunables... */struct files_stat_struct files_stat = {	.max_files = NR_FILE}; /* SLAB cache for file structures */static struct kmem_cache *filp_cachep __read_mostly; static struct percpu_counter nr_files __cacheline_aligned_in_smp; static void file_free_rcu(struct rcu_head *head){	struct file *f = container_of(head, struct file, f_u.fu_rcuhead); 	put_cred(f->f_cred);	kmem_cache_free(filp_cachep, f);} static inline void file_free(struct file *f){	security_file_free(f);	if (!(f->f_mode & FMODE_NOACCOUNT))		percpu_counter_dec(&nr_files);	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);} /* * Return the total number of open files in the system */static long get_nr_files(void){	return percpu_counter_read_positive(&nr_files);} /* * Return the maximum number of open files in the system */unsigned long get_max_files(void){	return files_stat.max_files;}EXPORT_SYMBOL_GPL(get_max_files); /* * Handle nr_files sysctl */#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)int proc_nr_files(struct ctl_table *table, int write,                     void *buffer, size_t *lenp, loff_t *ppos){	files_stat.nr_files = get_nr_files();	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);}#elseint proc_nr_files(struct ctl_table *table, int write,                     void *buffer, size_t *lenp, loff_t *ppos){	return -ENOSYS;}#endif static struct file *__alloc_file(int flags, const struct cred *cred){	struct file *f;	int error; 	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);	if (unlikely(!f))		return ERR_PTR(-ENOMEM); 	f->f_cred = get_cred(cred);	error = security_file_alloc(f);	if (unlikely(error)) {		file_free_rcu(&f->f_u.fu_rcuhead);		return ERR_PTR(error);	} 	atomic_long_set(&f->f_count, 1);	rwlock_init(&f->f_owner.lock);	spin_lock_init(&f->f_lock);	mutex_init(&f->f_pos_lock);	f->f_flags = flags;	f->f_mode = OPEN_FMODE(flags);	/* f->f_version: 0 */ 	return f;} /* Find an unused file structure and return a pointer to it. * Returns an error pointer if some error happend e.g. we over file * structures limit, run out of memory or operation is not permitted. * * Be very careful using this.  You are responsible for * getting write access to any mount that you might assign * to this filp, if it is opened for write.  If this is not * done, you will imbalance int the mount's writer count * and a warning at __fput() time. */struct file *alloc_empty_file(int flags, const struct cred *cred){	static long old_max;	struct file *f; 	/*	 * Privileged users can go above max_files	 */	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {		/*		 * percpu_counters are inaccurate.  Do an expensive check before		 * we go and fail.		 */		if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)			goto over;	} 	f = __alloc_file(flags, cred);	if (!IS_ERR(f))		percpu_counter_inc(&nr_files); 	return f; over:	/* Ran out of filps - report that */	if (get_nr_files() > old_max) {		pr_info("VFS: file-max limit %lu reached\n", get_max_files());		old_max = get_nr_files();	}	return ERR_PTR(-ENFILE);} /* * Variant of alloc_empty_file() that doesn't check and modify nr_files. * * Should not be used unless there's a very good reason to do so. */struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred){	struct file *f = __alloc_file(flags, cred); 	if (!IS_ERR(f))		f->f_mode |= FMODE_NOACCOUNT; 	return f;} /** * alloc_file - allocate and initialize a 'struct file' * * @path: the (dentry, vfsmount) pair for the new file * @flags: O_... flags with which the new file will be opened * @fop: the 'struct file_operations' for the new file */static struct file *alloc_file(const struct path *path, int flags,		const struct file_operations *fop){	struct file *file; 	file = alloc_empty_file(flags, current_cred());	if (IS_ERR(file))		return file; 	file->f_path = *path;	file->f_inode = path->dentry->d_inode;	file->f_mapping = path->dentry->d_inode->i_mapping;	file->f_wb_err = filemap_sample_wb_err(file->f_mapping);	file->f_sb_err = file_sample_sb_err(file);	if ((file->f_mode & FMODE_READ) &&	     likely(fop->read || fop->read_iter))		file->f_mode |= FMODE_CAN_READ;	if ((file->f_mode & FMODE_WRITE) &&	     likely(fop->write || fop->write_iter))		file->f_mode |= FMODE_CAN_WRITE;	file->f_mode |= FMODE_OPENED;	file->f_op = fop;	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)		i_readcount_inc(path->dentry->d_inode);	return file;} struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,				const char *name, int flags,				const struct file_operations *fops){	static const struct dentry_operations anon_ops = {		.d_dname = simple_dname	};	struct qstr this = QSTR_INIT(name, strlen(name));	struct path path;	struct file *file; 	path.dentry = d_alloc_pseudo(mnt->mnt_sb, &this);	if (!path.dentry)		return ERR_PTR(-ENOMEM);	if (!mnt->mnt_sb->s_d_op)		d_set_d_op(path.dentry, &anon_ops);	path.mnt = mntget(mnt);	d_instantiate(path.dentry, inode);	file = alloc_file(&path, flags, fops);	if (IS_ERR(file)) {		ihold(inode);		path_put(&path);	}	return file;}EXPORT_SYMBOL(alloc_file_pseudo); struct file *alloc_file_clone(struct file *base, int flags,				const struct file_operations *fops){	struct file *f = alloc_file(&base->f_path, flags, fops);	if (!IS_ERR(f)) {		path_get(&f->f_path);		f->f_mapping = base->f_mapping;	}	return f;} /* the real guts of fput() - releasing the last reference to file */static void __fput(struct file *file){	struct dentry *dentry = file->f_path.dentry;	struct vfsmount *mnt = file->f_path.mnt;	struct inode *inode = file->f_inode;	fmode_t mode = file->f_mode; 	if (unlikely(!(file->f_mode & FMODE_OPENED)))		goto out; 	might_sleep(); 	fsnotify_close(file);	/*	 * The function eventpoll_release() should be the first called	 * in the file cleanup chain.	 */	eventpoll_release(file);	locks_remove_file(file); 	ima_file_free(file);	if (unlikely(file->f_flags & FASYNC)) {		if (file->f_op->fasync)			file->f_op->fasync(-1, file, 0);	}	if (file->f_op->release)		file->f_op->release(inode, file);	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&		     !(mode & FMODE_PATH))) {		cdev_put(inode->i_cdev);	}	fops_put(file->f_op);	put_pid(file->f_owner.pid);	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)		i_readcount_dec(inode);	if (mode & FMODE_WRITER) {		put_write_access(inode);		__mnt_drop_write(mnt);	}	dput(dentry);	if (unlikely(mode & FMODE_NEED_UNMOUNT))		dissolve_on_fput(mnt);	mntput(mnt);out:	file_free(file);} static LLIST_HEAD(delayed_fput_list);static void delayed_fput(struct work_struct *unused){	struct llist_node *node = llist_del_all(&delayed_fput_list);	struct file *f, *t; 	llist_for_each_entry_safe(f, t, node, f_u.fu_llist)		__fput(f);} static void ____fput(struct callback_head *work){	__fput(container_of(work, struct file, f_u.fu_rcuhead));} /* * If kernel thread really needs to have the final fput() it has done * to complete, call this.  The only user right now is the boot - we * *do* need to make sure our writes to binaries on initramfs has * not left us with opened struct file waiting for __fput() - execve() * won't work without that.  Please, don't add more callers without * very good reasons; in particular, never call that with locks * held and never call that from a thread that might need to do * some work on any kind of umount. */void flush_delayed_fput(void){	delayed_fput(NULL);}EXPORT_SYMBOL_GPL(flush_delayed_fput); static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput); void fput_many(struct file *file, unsigned int refs){	if (atomic_long_sub_and_test(refs, &file->f_count)) {		struct task_struct *task = current; 		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {			init_task_work(&file->f_u.fu_rcuhead, ____fput);			if (!task_work_add(task, &file->f_u.fu_rcuhead, TWA_RESUME))				return;			/*			 * After this task has run exit_task_work(),			 * task_work_add() will fail.  Fall through to delayed			 * fput to avoid leaking *file.			 */		} 		if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))			schedule_delayed_work(&delayed_fput_work, 1);	}} void fput(struct file *file){	fput_many(file, 1);} /* * synchronous analog of fput(); for kernel threads that might be needed * in some umount() (and thus can't use flush_delayed_fput() without * risking deadlocks), need to wait for completion of __fput() and know * for this specific struct file it won't involve anything that would * need them.  Use only if you really need it - at the very least, * don't blindly convert fput() by kernel thread to that. */void __fput_sync(struct file *file){	if (atomic_long_dec_and_test(&file->f_count)) {		struct task_struct *task = current;		BUG_ON(!(task->flags & PF_KTHREAD));		__fput(file);	}} EXPORT_SYMBOL(fput); void __init files_init(void){	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);	percpu_counter_init(&nr_files, 0, GFP_KERNEL);} /* * One file with associated inode and dcache is very roughly 1K. Per default * do not use more than 10% of our memory for files. */void __init files_maxfiles_init(void){	unsigned long n;	unsigned long nr_pages = totalram_pages();	unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2; 	memreserve = min(memreserve, nr_pages - 1);	n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10; 	files_stat.max_files = max_t(unsigned long, n, NR_FILE);}