1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * descriptor table internals; you almost certainly want file.h instead. 4 */ 5 6 #ifndef __LINUX_FDTABLE_H 7 #define __LINUX_FDTABLE_H 8 9 #include <linux/posix_types.h> 10 #include <linux/compiler.h> 11 #include <linux/spinlock.h> 12 #include <linux/rcupdate.h> 13 #include <linux/nospec.h> 14 #include <linux/types.h> 15 #include <linux/init.h> 16 #include <linux/fs.h> 17 18 #include <linux/atomic.h> 19 20 /* 21 * The default fd array needs to be at least BITS_PER_LONG, 22 * as this is the granularity returned by copy_fdset(). 23 */ 24 #define NR_OPEN_DEFAULT BITS_PER_LONG 25 #define NR_OPEN_MAX ~0U 26 27 struct fdtable { 28 unsigned int max_fds; 29 struct file __rcu **fd; /* current fd array */ 30 unsigned long *close_on_exec; 31 unsigned long *open_fds; 32 unsigned long *full_fds_bits; 33 struct rcu_head rcu; 34 }; 35 36 /* 37 * Open file table structure 38 */ 39 struct files_struct { 40 /* 41 * read mostly part 42 */ 43 atomic_t count; 44 bool resize_in_progress; 45 wait_queue_head_t resize_wait; 46 47 struct fdtable __rcu *fdt; 48 struct fdtable fdtab; 49 /* 50 * written part on a separate cache line in SMP 51 */ 52 spinlock_t file_lock ____cacheline_aligned_in_smp; 53 unsigned int next_fd; 54 unsigned long close_on_exec_init[1]; 55 unsigned long open_fds_init[1]; 56 unsigned long full_fds_bits_init[1]; 57 struct file __rcu * fd_array[NR_OPEN_DEFAULT]; 58 }; 59 60 struct file_operations; 61 struct vfsmount; 62 struct dentry; 63 64 #define rcu_dereference_check_fdtable(files, fdtfd) \ 65 rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock)) 66 67 #define files_fdtable(files) \ 68 rcu_dereference_check_fdtable((files), (files)->fdt) 69 70 /* 71 * The caller must ensure that fd table isn't shared or hold rcu or file lock 72 */ 73 static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd) 74 { 75 struct fdtable *fdt = rcu_dereference_raw(files->fdt); 76 unsigned long mask = array_index_mask_nospec(fd, fdt->max_fds); 77 struct file *needs_masking; 78 79 /* 80 * 'mask' is zero for an out-of-bounds fd, all ones for ok. 81 * 'fd&mask' is 'fd' for ok, or 0 for out of bounds. 82 * 83 * Accessing fdt->fd[0] is ok, but needs masking of the result. 84 */ 85 needs_masking = rcu_dereference_raw(fdt->fd[fd&mask]); 86 return (struct file *)(mask & (unsigned long)needs_masking); 87 } 88 89 static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd) 90 { 91 RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock), 92 "suspicious rcu_dereference_check() usage"); 93 return files_lookup_fd_raw(files, fd); 94 } 95 96 struct file *lookup_fdget_rcu(unsigned int fd); 97 struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd); 98 struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *fd); 99 100 static inline bool close_on_exec(unsigned int fd, const struct files_struct *files) 101 { 102 return test_bit(fd, files_fdtable(files)->close_on_exec); 103 } 104 105 struct task_struct; 106 107 void put_files_struct(struct files_struct *fs); 108 int unshare_files(void); 109 struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy; 110 void do_close_on_exec(struct files_struct *); 111 int iterate_fd(struct files_struct *, unsigned, 112 int (*)(const void *, struct file *, unsigned), 113 const void *); 114 115 extern int close_fd(unsigned int fd); 116 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags); 117 extern struct file *file_close_fd(unsigned int fd); 118 extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, 119 struct files_struct **new_fdp); 120 121 extern struct kmem_cache *files_cachep; 122 123 #endif /* __LINUX_FDTABLE_H */ 124