From bd9b51e79cb0b8bc00a7e0076a4a8963ca4a797c Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 18 Nov 2014 23:38:21 -0500 Subject: 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 --- fs/inode.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'fs/inode.c') diff --git a/fs/inode.c b/fs/inode.c index 26753ba7b6d6..5b83ef7fc8d5 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, -- cgit v1.2.3