Commit 48a6aba3 authored by Al Viro's avatar Al Viro Committed by Luis Henriques

procfs: fix race between symlink removals and traversals

commit 7e0e953b upstream.

use_pde()/unuse_pde() in ->follow_link()/->put_link() resp.
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 67083b7b
...@@ -19,7 +19,6 @@ ...@@ -19,7 +19,6 @@
#include <linux/mount.h> #include <linux/mount.h>
#include <linux/init.h> #include <linux/init.h>
#include <linux/idr.h> #include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h> #include <linux/bitops.h>
#include <linux/spinlock.h> #include <linux/spinlock.h>
#include <linux/completion.h> #include <linux/completion.h>
...@@ -162,17 +161,6 @@ void proc_free_inum(unsigned int inum) ...@@ -162,17 +161,6 @@ void proc_free_inum(unsigned int inum)
spin_unlock_irqrestore(&proc_inum_lock, flags); spin_unlock_irqrestore(&proc_inum_lock, flags);
} }
static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
{
nd_set_link(nd, __PDE_DATA(dentry->d_inode));
return NULL;
}
static const struct inode_operations proc_link_inode_operations = {
.readlink = generic_readlink,
.follow_link = proc_follow_link,
};
/* /*
* Don't create negative dentries here, return -ENOENT by hand * Don't create negative dentries here, return -ENOENT by hand
* instead. * instead.
......
...@@ -23,6 +23,7 @@ ...@@ -23,6 +23,7 @@
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/mount.h> #include <linux/mount.h>
#include <linux/magic.h> #include <linux/magic.h>
#include <linux/namei.h>
#include <asm/uaccess.h> #include <asm/uaccess.h>
...@@ -401,6 +402,26 @@ static const struct file_operations proc_reg_file_ops_no_compat = { ...@@ -401,6 +402,26 @@ static const struct file_operations proc_reg_file_ops_no_compat = {
}; };
#endif #endif
static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
{
struct proc_dir_entry *pde = PDE(dentry->d_inode);
if (unlikely(!use_pde(pde)))
return ERR_PTR(-EINVAL);
nd_set_link(nd, pde->data);
return pde;
}
static void proc_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
{
unuse_pde(p);
}
const struct inode_operations proc_link_inode_operations = {
.readlink = generic_readlink,
.follow_link = proc_follow_link,
.put_link = proc_put_link,
};
struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de) struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
{ {
struct inode *inode = new_inode_pseudo(sb); struct inode *inode = new_inode_pseudo(sb);
......
...@@ -202,6 +202,7 @@ struct pde_opener { ...@@ -202,6 +202,7 @@ struct pde_opener {
int closing; int closing;
struct completion *c; struct completion *c;
}; };
extern const struct inode_operations proc_link_inode_operations;
extern const struct inode_operations proc_pid_link_inode_operations; extern const struct inode_operations proc_pid_link_inode_operations;
......
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