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Commit 7e0e953b authored by Al Viro's avatar Al Viro
Browse files

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: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 0db59e59

fs/proc/generic.c

+0 −12
Original line number Diff line number Diff line
@@ -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.

fs/proc/inode.c

+21 −0
Original line number Diff line number Diff line
@@ -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);

fs/proc/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -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;