From bd9b51e79cb0b8bc00a7e0076a4a8963ca4a797c Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 18 Nov 2014 23:38:21 -0500 Subject: [PATCH] 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: Al Viro --- arch/ia64/kernel/perfmon.c | 10 ---------- fs/inode.c | 11 ++++++++--- include/linux/fs.h | 1 - net/Makefile | 2 -- net/nonet.c | 26 -------------------------- net/socket.c | 19 ------------------- 6 files changed, 8 insertions(+), 61 deletions(-) delete mode 100644 net/nonet.c diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c index 5845ffe..ac4528f 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 26753ba..5b83ef7 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -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, diff --git a/include/linux/fs.h b/include/linux/fs.h index 2beddc2..b37beaf 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -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); diff --git a/net/Makefile b/net/Makefile index 7ed1970..1f6c3e4 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 -#include -#include -#include -#include - -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 fe20c31..850f6c3 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 -- 1.9.1