34dbbcdbf6
A lot of seqfile users seem to be using things like %pK that uses the credentials of the current process, but that is actually completely wrong for filesystem interfaces. The unix semantics for permission checking files is to check permissions at _open_ time, not at read or write time, and that is not just a small detail: passing off stdin/stdout/stderr to a suid application and making the actual IO happen in privileged context is a classic exploit technique. So if we want to be able to look at permissions at read time, we need to use the file open credentials, not the current ones. Normal file accesses can just use "f_cred" (or any of the helper functions that do that, like file_ns_capable()), but the seqfile interfaces do not have any such options. It turns out that seq_file _does_ save away the user_ns information of the file, though. Since user_ns is just part of the full credential information, replace that special case with saving off the cred pointer instead, and suddenly seq_file has all the permission information it needs. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
224 lines
6.6 KiB
C
224 lines
6.6 KiB
C
#ifndef _LINUX_SEQ_FILE_H
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#define _LINUX_SEQ_FILE_H
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#include <linux/types.h>
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#include <linux/string.h>
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#include <linux/bug.h>
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#include <linux/mutex.h>
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#include <linux/cpumask.h>
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#include <linux/nodemask.h>
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#include <linux/fs.h>
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#include <linux/cred.h>
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struct seq_operations;
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struct seq_file {
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char *buf;
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size_t size;
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size_t from;
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size_t count;
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size_t pad_until;
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loff_t index;
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loff_t read_pos;
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u64 version;
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struct mutex lock;
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const struct seq_operations *op;
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int poll_event;
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const struct file *file;
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void *private;
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};
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struct seq_operations {
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void * (*start) (struct seq_file *m, loff_t *pos);
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void (*stop) (struct seq_file *m, void *v);
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void * (*next) (struct seq_file *m, void *v, loff_t *pos);
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int (*show) (struct seq_file *m, void *v);
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};
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#define SEQ_SKIP 1
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/**
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* seq_has_overflowed - check if the buffer has overflowed
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* @m: the seq_file handle
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*
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* seq_files have a buffer which may overflow. When this happens a larger
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* buffer is reallocated and all the data will be printed again.
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* The overflow state is true when m->count == m->size.
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*
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* Returns true if the buffer received more than it can hold.
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*/
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static inline bool seq_has_overflowed(struct seq_file *m)
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{
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return m->count == m->size;
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}
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/**
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* seq_get_buf - get buffer to write arbitrary data to
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* @m: the seq_file handle
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* @bufp: the beginning of the buffer is stored here
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*
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* Return the number of bytes available in the buffer, or zero if
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* there's no space.
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*/
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static inline size_t seq_get_buf(struct seq_file *m, char **bufp)
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{
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BUG_ON(m->count > m->size);
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if (m->count < m->size)
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*bufp = m->buf + m->count;
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else
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*bufp = NULL;
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return m->size - m->count;
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}
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/**
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* seq_commit - commit data to the buffer
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* @m: the seq_file handle
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* @num: the number of bytes to commit
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*
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* Commit @num bytes of data written to a buffer previously acquired
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* by seq_buf_get. To signal an error condition, or that the data
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* didn't fit in the available space, pass a negative @num value.
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*/
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static inline void seq_commit(struct seq_file *m, int num)
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{
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if (num < 0) {
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m->count = m->size;
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} else {
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BUG_ON(m->count + num > m->size);
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m->count += num;
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}
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}
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/**
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* seq_setwidth - set padding width
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* @m: the seq_file handle
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* @size: the max number of bytes to pad.
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*
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* Call seq_setwidth() for setting max width, then call seq_printf() etc. and
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* finally call seq_pad() to pad the remaining bytes.
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*/
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static inline void seq_setwidth(struct seq_file *m, size_t size)
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{
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m->pad_until = m->count + size;
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}
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void seq_pad(struct seq_file *m, char c);
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char *mangle_path(char *s, const char *p, const char *esc);
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int seq_open(struct file *, const struct seq_operations *);
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ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
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loff_t seq_lseek(struct file *, loff_t, int);
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int seq_release(struct inode *, struct file *);
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int seq_write(struct seq_file *seq, const void *data, size_t len);
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__printf(2, 0)
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void seq_vprintf(struct seq_file *m, const char *fmt, va_list args);
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__printf(2, 3)
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void seq_printf(struct seq_file *m, const char *fmt, ...);
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void seq_putc(struct seq_file *m, char c);
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void seq_puts(struct seq_file *m, const char *s);
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void seq_put_decimal_ull(struct seq_file *m, char delimiter,
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unsigned long long num);
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void seq_put_decimal_ll(struct seq_file *m, char delimiter, long long num);
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void seq_escape(struct seq_file *m, const char *s, const char *esc);
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void seq_hex_dump(struct seq_file *m, const char *prefix_str, int prefix_type,
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int rowsize, int groupsize, const void *buf, size_t len,
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bool ascii);
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int seq_path(struct seq_file *, const struct path *, const char *);
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int seq_file_path(struct seq_file *, struct file *, const char *);
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int seq_dentry(struct seq_file *, struct dentry *, const char *);
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int seq_path_root(struct seq_file *m, const struct path *path,
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const struct path *root, const char *esc);
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int single_open(struct file *, int (*)(struct seq_file *, void *), void *);
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int single_open_size(struct file *, int (*)(struct seq_file *, void *), void *, size_t);
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int single_release(struct inode *, struct file *);
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void *__seq_open_private(struct file *, const struct seq_operations *, int);
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int seq_open_private(struct file *, const struct seq_operations *, int);
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int seq_release_private(struct inode *, struct file *);
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static inline struct user_namespace *seq_user_ns(struct seq_file *seq)
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{
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#ifdef CONFIG_USER_NS
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return seq->file->f_cred->user_ns;
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#else
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extern struct user_namespace init_user_ns;
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return &init_user_ns;
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#endif
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}
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/**
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* seq_show_options - display mount options with appropriate escapes.
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* @m: the seq_file handle
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* @name: the mount option name
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* @value: the mount option name's value, can be NULL
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*/
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static inline void seq_show_option(struct seq_file *m, const char *name,
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const char *value)
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{
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seq_putc(m, ',');
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seq_escape(m, name, ",= \t\n\\");
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if (value) {
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seq_putc(m, '=');
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seq_escape(m, value, ", \t\n\\");
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}
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}
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/**
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* seq_show_option_n - display mount options with appropriate escapes
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* where @value must be a specific length.
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* @m: the seq_file handle
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* @name: the mount option name
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* @value: the mount option name's value, cannot be NULL
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* @length: the length of @value to display
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*
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* This is a macro since this uses "length" to define the size of the
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* stack buffer.
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*/
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#define seq_show_option_n(m, name, value, length) { \
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char val_buf[length + 1]; \
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strncpy(val_buf, value, length); \
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val_buf[length] = '\0'; \
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seq_show_option(m, name, val_buf); \
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}
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#define SEQ_START_TOKEN ((void *)1)
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/*
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* Helpers for iteration over list_head-s in seq_files
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*/
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extern struct list_head *seq_list_start(struct list_head *head,
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loff_t pos);
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extern struct list_head *seq_list_start_head(struct list_head *head,
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loff_t pos);
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extern struct list_head *seq_list_next(void *v, struct list_head *head,
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loff_t *ppos);
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/*
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* Helpers for iteration over hlist_head-s in seq_files
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*/
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extern struct hlist_node *seq_hlist_start(struct hlist_head *head,
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loff_t pos);
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extern struct hlist_node *seq_hlist_start_head(struct hlist_head *head,
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loff_t pos);
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extern struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
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loff_t *ppos);
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extern struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
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loff_t pos);
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extern struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
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loff_t pos);
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extern struct hlist_node *seq_hlist_next_rcu(void *v,
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struct hlist_head *head,
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loff_t *ppos);
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/* Helpers for iterating over per-cpu hlist_head-s in seq_files */
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extern struct hlist_node *seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos);
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extern struct hlist_node *seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head, int *cpu, loff_t *pos);
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#endif
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