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 static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt) 37 { 38 return test_bit(fd, fdt->close_on_exec); 39 } 40 41 static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt) 42 { 43 return test_bit(fd, fdt->open_fds); 44 } 45 46 /* 47 * Open file table structure 48 */ 49 struct files_struct { 50 /* 51 * read mostly part 52 */ 53 atomic_t count; 54 bool resize_in_progress; 55 wait_queue_head_t resize_wait; 56 57 struct fdtable __rcu *fdt; 58 struct fdtable fdtab; 59 /* 60 * written part on a separate cache line in SMP 61 */ 62 spinlock_t file_lock ____cacheline_aligned_in_smp; 63 unsigned int next_fd; 64 unsigned long close_on_exec_init[1]; 65 unsigned long open_fds_init[1]; 66 unsigned long full_fds_bits_init[1]; 67 struct file __rcu * fd_array[NR_OPEN_DEFAULT]; 68 }; 69 70 struct file_operations; 71 struct vfsmount; 72 struct dentry; 73 74 #define rcu_dereference_check_fdtable(files, fdtfd) \ 75 rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock)) 76 77 #define files_fdtable(files) \ 78 rcu_dereference_check_fdtable((files), (files)->fdt) 79 80 /* 81 * The caller must ensure that fd table isn't shared or hold rcu or file lock 82 */ 83 static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd) 84 { 85 struct fdtable *fdt = rcu_dereference_raw(files->fdt); 86 unsigned long mask = array_index_mask_nospec(fd, fdt->max_fds); 87 struct file *needs_masking; 88 89 /* 90 * 'mask' is zero for an out-of-bounds fd, all ones for ok. 91 * 'fd&mask' is 'fd' for ok, or 0 for out of bounds. 92 * 93 * Accessing fdt->fd[0] is ok, but needs masking of the result. 94 */ 95 needs_masking = rcu_dereference_raw(fdt->fd[fd&mask]); 96 return (struct file *)(mask & (unsigned long)needs_masking); 97 } 98 99 static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd) 100 { 101 RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock), 102 "suspicious rcu_dereference_check() usage"); 103 return files_lookup_fd_raw(files, fd); 104 } 105 106 struct file *lookup_fdget_rcu(unsigned int fd); 107 struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd); 108 struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *fd); 109 110 struct task_struct; 111 112 void put_files_struct(struct files_struct *fs); 113 int unshare_files(void); 114 struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy; 115 void do_close_on_exec(struct files_struct *); 116 int iterate_fd(struct files_struct *, unsigned, 117 int (*)(const void *, struct file *, unsigned), 118 const void *); 119 120 extern int close_fd(unsigned int fd); 121 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags); 122 extern struct file *file_close_fd(unsigned int fd); 123 extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, 124 struct files_struct **new_fdp); 125 126 extern struct kmem_cache *files_cachep; 127 128 #endif /* __LINUX_FDTABLE_H */ 129