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 */
files_lookup_fd_raw(struct files_struct * files,unsigned int fd)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
files_lookup_fd_locked(struct files_struct * files,unsigned int fd)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 struct file *lookup_fdget_rcu(unsigned int fd);
96 struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd);
97 struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *fd);
98
close_on_exec(unsigned int fd,const struct files_struct * files)99 static inline bool close_on_exec(unsigned int fd, const struct files_struct *files)
100 {
101 return test_bit(fd, files_fdtable(files)->close_on_exec);
102 }
103
104 struct task_struct;
105
106 void put_files_struct(struct files_struct *fs);
107 int unshare_files(void);
108 struct fd_range {
109 unsigned int from, to;
110 };
111 struct files_struct *dup_fd(struct files_struct *, struct fd_range *) __latent_entropy;
112 void do_close_on_exec(struct files_struct *);
113 int iterate_fd(struct files_struct *, unsigned,
114 int (*)(const void *, struct file *, unsigned),
115 const void *);
116
117 extern int close_fd(unsigned int fd);
118 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
119 extern struct file *file_close_fd(unsigned int fd);
120
121 extern struct kmem_cache *files_cachep;
122
123 #endif /* __LINUX_FDTABLE_H */
124