Commit bd9b51e7 authored by Al Viro's avatar Al Viro
Browse files

make default ->i_fop have ->open() fail with ENXIO 



As it is, default ->i_fop has NULL ->open() (along with all other methods).
The only case where it matters is reopening (via procfs symlink) a file that
didn't get its ->f_op from ->i_fop - anything else will have ->i_fop assigned
to something sane (default would fail on read/write/ioctl/etc.).

	Unfortunately, such case exists - alloc_file() users, especially
anon_get_file() ones.  There we have tons of opened files of very different
kinds sharing the same inode.  As the result, attempt to reopen those via
procfs succeeds and you get a descriptor you can't do anything with.

	Moreover, in case of sockets we set ->i_fop that will only be used
on such reopen attempts - and put a failing ->open() into it to make sure
those do not succeed.

	It would be simpler to put such ->open() into default ->i_fop and leave
it unchanged both for anon inode (as we do anyway) and for socket ones.  Result:
	* everything going through do_dentry_open() works as it used to
	* sock_no_open() kludge is gone
	* attempts to reopen anon-inode files fail as they really ought to
	* ditto for aio_private_file()
	* ditto for perfmon - this one actually tried to imitate sock_no_open()
trick, but failed to set ->i_fop, so in the current tree reopens succeed and
yield completely useless descriptor.  Intent clearly had been to fail with
-ENXIO on such reopens; now it actually does.
	* everything else that used alloc_file() keeps working - it has ->i_fop
set for its inodes anyway

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 1f55a6ec

arch/ia64/kernel/perfmon.c

+0 −10
Original line number Diff line number Diff line
@@ -2145,22 +2145,12 @@ doit: 
	return 0;

}



static int

pfm_no_open(struct inode *irrelevant, struct file *dontcare)

{

	DPRINT(("pfm_no_open called\n"));

	return -ENXIO;

}







static const struct file_operations pfm_file_ops = {

	.llseek		= no_llseek,

	.read		= pfm_read,

	.write		= pfm_write,

	.poll		= pfm_poll,

	.unlocked_ioctl = pfm_ioctl,

	.open		= pfm_no_open,	/* special open code to disallow open via /proc */

	.fasync		= pfm_fasync,

	.release	= pfm_close,

	.flush		= pfm_flush

fs/inode.c

+8 −3
Original line number Diff line number Diff line
@@ -114,6 +114,11 @@ int proc_nr_inodes(struct ctl_table *table, int write, 
}

#endif



static int no_open(struct inode *inode, struct file *file)

{

	return -ENXIO;

}



/**

 * inode_init_always - perform inode structure intialisation

 * @sb: superblock inode belongs to
@@ -125,7 +130,7 @@ int proc_nr_inodes(struct ctl_table *table, int write, 
int inode_init_always(struct super_block *sb, struct inode *inode)

{

	static const struct inode_operations empty_iops;

	static const struct file_operations empty_fops;

	static const struct file_operations no_open_fops = {.open = no_open};

	struct address_space *const mapping = &inode->i_data;



	inode->i_sb = sb;
@@ -133,7 +138,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode) 
	inode->i_flags = 0;

	atomic_set(&inode->i_count, 1);

	inode->i_op = &empty_iops;

	inode->i_fop = &empty_fops;

	inode->i_fop = &no_open_fops;

	inode->__i_nlink = 1;

	inode->i_opflags = 0;

	i_uid_write(inode, 0);
@@ -1801,7 +1806,7 @@ void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev) 
	} else if (S_ISFIFO(mode))

		inode->i_fop = &pipefifo_fops;

	else if (S_ISSOCK(mode))

		inode->i_fop = &bad_sock_fops;

		;	/* leave it no_open_fops */

	else

		printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"

				  " inode %s:%lu\n", mode, inode->i_sb->s_id,

include/linux/fs.h

+0 −1
Original line number Diff line number Diff line
@@ -2151,7 +2151,6 @@ static inline int sb_is_blkdev_sb(struct super_block *sb) 
extern int sync_filesystem(struct super_block *);

extern const struct file_operations def_blk_fops;

extern const struct file_operations def_chr_fops;

extern const struct file_operations bad_sock_fops;

#ifdef CONFIG_BLOCK

extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);

extern int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);

net/Makefile

+0 −2
Original line number Diff line number Diff line
@@ -5,8 +5,6 @@ 
# Rewritten to use lists instead of if-statements.

#



obj-y	:= nonet.o



obj-$(CONFIG_NET)		:= socket.o core/



tmp-$(CONFIG_COMPAT) 		:= compat.o

net/nonet.c

deleted100644 → 0
+0 −26
Original line number Diff line number Diff line 
/*

 * net/nonet.c

 *

 * Dummy functions to allow us to configure network support entirely

 * out of the kernel.

 *

 * Distributed under the terms of the GNU GPL version 2.

 * Copyright (c) Matthew Wilcox 2003

 */



#include <linux/module.h>

#include <linux/errno.h>

#include <linux/fs.h>

#include <linux/init.h>

#include <linux/kernel.h>



static int sock_no_open(struct inode *irrelevant, struct file *dontcare)

{

	return -ENXIO;

}



const struct file_operations bad_sock_fops = {

	.owner = THIS_MODULE,

	.open = sock_no_open,

	.llseek = noop_llseek,

};

CRA Git | Maintained and supported by SUSTech CRA and CCSE