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
close_on_exec(unsigned int fd,const struct fdtable * fdt)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
fd_is_open(unsigned int fd,const struct fdtable * fdt)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 */
files_lookup_fd_raw(struct files_struct * files,unsigned int fd)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
files_lookup_fd_locked(struct files_struct * files,unsigned int fd)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