[Devel] [PATCH 13/13] make default ->i_fop have ->open() fail with ENXIO
Andrew Vagin
avagin at openvz.org
Tue Oct 13 09:10:37 PDT 2015
ML: bd9b51e79cb0b8bc00a7e0076a4a8963ca4a797c
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: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Andrew Vagin <avagin at openvz.org>
---
arch/ia64/kernel/perfmon.c | 10 ----------
fs/inode.c | 12 +++++++++---
include/linux/fs.h | 1 -
net/Makefile | 2 --
net/nonet.c | 26 --------------------------
net/socket.c | 19 -------------------
6 files changed, 9 insertions(+), 61 deletions(-)
delete mode 100644 net/nonet.c
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 9ea25fc..4334a96 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -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
diff --git a/fs/inode.c b/fs/inode.c
index 960cd15..6c27178 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -121,6 +121,11 @@ int proc_nr_inodes(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
@@ -131,7 +136,8 @@ int proc_nr_inodes(ctl_table *table, int write,
*/
int inode_init_always(struct super_block *sb, struct inode *inode)
{
- static const struct file_operations empty_fops;
+ static const struct inode_operations empty_iops;
+ static const struct file_operations no_open_fops = {.open = no_open};
struct address_space *const mapping = &inode->i_data;
inode->i_sb = sb;
@@ -139,7 +145,7 @@ 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);
@@ -1900,7 +1906,7 @@ 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,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cd3db97..c1c7b5d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2436,7 +2436,6 @@ 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);
diff --git a/net/Makefile b/net/Makefile
index 9492e8c..2c98197 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -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
diff --git a/net/nonet.c b/net/nonet.c
deleted file mode 100644
index b1a73fd..0000000
--- a/net/nonet.c
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * 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,
-};
diff --git a/net/socket.c b/net/socket.c
index df73b9d..59b0780 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -113,7 +113,6 @@ unsigned int sysctl_net_busy_read __read_mostly;
unsigned int sysctl_net_busy_poll __read_mostly;
#endif
-static int sock_no_open(struct inode *irrelevant, struct file *dontcare);
static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos);
static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
@@ -151,7 +150,6 @@ static const struct file_operations socket_file_ops = {
.compat_ioctl = compat_sock_ioctl,
#endif
.mmap = sock_mmap,
- .open = sock_no_open, /* special open code to disallow open via /proc */
.release = sock_close,
.fasync = sock_fasync,
.sendpage = sock_sendpage,
@@ -559,23 +557,6 @@ static struct socket *sock_alloc(void)
return sock;
}
-/*
- * In theory you can't get an open on this inode, but /proc provides
- * a back door. Remember to keep it shut otherwise you'll let the
- * creepy crawlies in.
- */
-
-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,
-};
-
/**
* sock_release - close a socket
* @sock: socket to close
--
1.7.1
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