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userns: Make seq_file's user namespace accessible

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struct file already has a user namespace associated with it
in file->f_cred->user_ns, unfortunately because struct
seq_file has no struct file backpointer associated with
it, it is difficult to get at the user namespace in seq_file
context.  Therefore add a helper function seq_user_ns to return
the associated user namespace and a user_ns field to struct
seq_file to be used in implementing seq_user_ns.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-05-23 18:01:20 -06:00
parent fc5795c8a9
commit adb37c4c67
2 changed files with 18 additions and 0 deletions
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4
fs/seq_file.c
View File

@ -9,6 +9,7 @@
#include <linux/export.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <asm/uaccess.h>
#include <asm/page.h>
@ -56,6 +57,9 @@ int seq_open(struct file *file, const struct seq_operations *op)
memset(p, 0, sizeof(*p));
mutex_init(&p->lock);
p->op = op;
#ifdef CONFIG_USER_NS
p->user_ns = file->f_cred->user_ns;
#endif
/*
* Wrappers around seq_open(e.g. swaps_open) need to be

14
include/linux/seq_file.h
View File

@ -13,6 +13,7 @@ struct file;
struct path;
struct inode;
struct dentry;
struct user_namespace;
struct seq_file {
char *buf;
@ -25,6 +26,9 @@ struct seq_file {
struct mutex lock;
const struct seq_operations *op;
int poll_event;
#ifdef CONFIG_USER_NS
struct user_namespace *user_ns;
#endif
void *private;
};
@ -128,6 +132,16 @@ int seq_put_decimal_ull(struct seq_file *m, char delimiter,
int seq_put_decimal_ll(struct seq_file *m, char delimiter,
long long num);
static inline struct user_namespace *seq_user_ns(struct seq_file *seq)
{
#ifdef CONFIG_USER_NS
return seq->user_ns;
#else
extern struct user_namespace init_user_ns;
return &init_user_ns;
#endif
}
#define SEQ_START_TOKEN ((void *)1)
/*
* Helpers for iteration over list_head-s in seq_files