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 26 struct fdtable { 27 unsigned int max_fds; 28 struct file __rcu **fd; /* current fd array */ 29 unsigned long *close_on_exec; 30 unsigned long *open_fds; 31 unsigned long *full_fds_bits; 32 struct rcu_head rcu; 33 }; 34 35 /* 36 * Open file table structure 37 */ 38 struct files_struct { 39 /* 40 * read mostly part 41 */ 42 atomic_t count; 43 bool resize_in_progress; 44 wait_queue_head_t resize_wait; 45 46 struct fdtable __rcu *fdt; 47 struct fdtable fdtab; 48 /* 49 * written part on a separate cache line in SMP 50 */ 51 spinlock_t file_lock ____cacheline_aligned_in_smp; 52 unsigned int next_fd; 53 unsigned long close_on_exec_init[1]; 54 unsigned long open_fds_init[1]; 55 unsigned long full_fds_bits_init[1]; 56 struct file __rcu * fd_array[NR_OPEN_DEFAULT]; 57 }; 58 59 struct file_operations; 60 struct vfsmount; 61 struct dentry; 62 63 #define rcu_dereference_check_fdtable(files, fdtfd) \ 64 rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock)) 65 66 #define files_fdtable(files) \ 67 rcu_dereference_check_fdtable((files), (files)->fdt) 68 69 /* 70 * The caller must ensure that fd table isn't shared or hold rcu or file lock 71 */ 72 static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd) 73 { 74 struct fdtable *fdt = rcu_dereference_raw(files->fdt); 75 unsigned long mask = array_index_mask_nospec(fd, fdt->max_fds); 76 struct file *needs_masking; 77 78 /* 79 * 'mask' is zero for an out-of-bounds fd, all ones for ok. 80 * 'fd&mask' is 'fd' for ok, or 0 for out of bounds. 81 * 82 * Accessing fdt->fd[0] is ok, but needs masking of the result. 83 */ 84 needs_masking = rcu_dereference_raw(fdt->fd[fd&mask]); 85 return (struct file *)(mask & (unsigned long)needs_masking); 86 } 87 88 static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd) 89 { 90 RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock), 91 "suspicious rcu_dereference_check() usage"); 92 return files_lookup_fd_raw(files, fd); 93 } 94 95 static inline bool close_on_exec(unsigned int fd, const struct files_struct *files) 96 { 97 return test_bit(fd, files_fdtable(files)->close_on_exec); 98 } 99 100 struct task_struct; 101 102 void put_files_struct(struct files_struct *fs); 103 int unshare_files(void); 104 struct fd_range { 105 unsigned int from, to; 106 }; 107 struct files_struct *dup_fd(struct files_struct *, struct fd_range *) __latent_entropy; 108 void do_close_on_exec(struct files_struct *); 109 int iterate_fd(struct files_struct *, unsigned, 110 int (*)(const void *, struct file *, unsigned), 111 const void *); 112 113 extern int close_fd(unsigned int fd); 114 extern struct file *file_close_fd(unsigned int fd); 115 116 extern struct kmem_cache *files_cachep; 117 118 #endif /* __LINUX_FDTABLE_H */ 119