forked from mirrors/linux
6319194ec5
Currently we have 3 primitives for removing an opened file from descriptor
table - pick_file(), __close_fd_get_file() and close_fd_get_file(). Their
calling conventions are rather odd and there's a code duplication for no
good reason. They can be unified -
1) have __range_close() cap max_fd in the very beginning; that way
we don't need separate way for pick_file() to report being past the end
of descriptor table.
2) make {__,}close_fd_get_file() return file (or NULL) directly, rather
than returning it via struct file ** argument. Don't bother with
(bogus) return value - nobody wants that -ENOENT.
3) make pick_file() return NULL on unopened descriptor - the only caller
that used to care about the distinction between descriptor past the end
of descriptor table and finding NULL in descriptor table doesn't give
a damn after (1).
4) lift ->files_lock out of pick_file()
That actually simplifies the callers, as well as the primitives themselves.
Code duplication is also gone...
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
134 lines
3.6 KiB
C
134 lines
3.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* descriptor table internals; you almost certainly want file.h instead.
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*/
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#ifndef __LINUX_FDTABLE_H
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#define __LINUX_FDTABLE_H
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#include <linux/posix_types.h>
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#include <linux/compiler.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/nospec.h>
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#include <linux/types.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/atomic.h>
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/*
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* The default fd array needs to be at least BITS_PER_LONG,
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* as this is the granularity returned by copy_fdset().
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*/
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#define NR_OPEN_DEFAULT BITS_PER_LONG
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#define NR_OPEN_MAX ~0U
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struct fdtable {
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unsigned int max_fds;
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struct file __rcu **fd; /* current fd array */
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unsigned long *close_on_exec;
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unsigned long *open_fds;
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unsigned long *full_fds_bits;
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struct rcu_head rcu;
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};
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static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
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{
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return test_bit(fd, fdt->close_on_exec);
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}
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static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
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{
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return test_bit(fd, fdt->open_fds);
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}
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/*
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* Open file table structure
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*/
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struct files_struct {
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/*
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* read mostly part
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*/
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atomic_t count;
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bool resize_in_progress;
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wait_queue_head_t resize_wait;
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struct fdtable __rcu *fdt;
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struct fdtable fdtab;
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/*
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* written part on a separate cache line in SMP
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*/
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spinlock_t file_lock ____cacheline_aligned_in_smp;
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unsigned int next_fd;
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unsigned long close_on_exec_init[1];
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unsigned long open_fds_init[1];
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unsigned long full_fds_bits_init[1];
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struct file __rcu * fd_array[NR_OPEN_DEFAULT];
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};
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struct file_operations;
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struct vfsmount;
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struct dentry;
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#define rcu_dereference_check_fdtable(files, fdtfd) \
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rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
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#define files_fdtable(files) \
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rcu_dereference_check_fdtable((files), (files)->fdt)
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/*
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* The caller must ensure that fd table isn't shared or hold rcu or file lock
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*/
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static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd)
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{
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struct fdtable *fdt = rcu_dereference_raw(files->fdt);
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if (fd < fdt->max_fds) {
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fd = array_index_nospec(fd, fdt->max_fds);
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return rcu_dereference_raw(fdt->fd[fd]);
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}
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return NULL;
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}
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static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd)
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{
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RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock),
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"suspicious rcu_dereference_check() usage");
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return files_lookup_fd_raw(files, fd);
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}
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static inline struct file *files_lookup_fd_rcu(struct files_struct *files, unsigned int fd)
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{
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RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
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"suspicious rcu_dereference_check() usage");
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return files_lookup_fd_raw(files, fd);
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}
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static inline struct file *lookup_fd_rcu(unsigned int fd)
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{
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return files_lookup_fd_rcu(current->files, fd);
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}
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struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd);
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struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *fd);
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struct task_struct;
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void put_files_struct(struct files_struct *fs);
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int unshare_files(void);
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struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy;
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void do_close_on_exec(struct files_struct *);
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int iterate_fd(struct files_struct *, unsigned,
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int (*)(const void *, struct file *, unsigned),
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const void *);
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extern int close_fd(unsigned int fd);
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extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
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extern struct file *close_fd_get_file(unsigned int fd);
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extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
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struct files_struct **new_fdp);
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extern struct kmem_cache *files_cachep;
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#endif /* __LINUX_FDTABLE_H */
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