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procfs: fix race between symlink removals and traversals 

use_pde()/unuse_pde() in ->follow_link()/->put_link() resp.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2015-02-21 22:16:11 -05:00
parent 0db59e5929
commit 7e0e953bb0
3 changed files with 22 additions and 12 deletions
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12
fs/proc/generic.c
View File

@ -19,7 +19,6 @@
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
@ -223,17 +222,6 @@ void proc_free_inum(unsigned int inum)
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
* instead.

21
fs/proc/inode.c
View File

@ -23,6 +23,7 @@
#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/magic.h>
#include <linux/namei.h>
#include <asm/uaccess.h>
@ -393,6 +394,26 @@ static const struct file_operations proc_reg_file_ops_no_compat = {
};
#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 *inode = new_inode_pseudo(sb);

1
fs/proc/internal.h
View File

@ -200,6 +200,7 @@ struct pde_opener {
int closing;
struct completion *c;
};
extern const struct inode_operations proc_link_inode_operations;
extern const struct inode_operations proc_pid_link_inode_operations;