fix bad_inode_ops memory corruption (CVE-2006-5753)

CVE-2006-5753 is for a case where an inode can be marked bad, switching
the ops to bad_inode_ops, which are all connected as:

static int return_EIO(void)
{
        return -EIO;
}

#define EIO_ERROR ((void *) (return_EIO))

static struct inode_operations bad_inode_ops =
{
        .create         = bad_inode_create
...etc...

The problem here is that the void cast causes return types to not be
promoted, and for ops such as listxattr which expect more than 32 bits of
return value, the 32-bit -EIO is interpreted as a large positive 64-bit
number, i.e. 0x00000000fffffffa instead of 0xfffffffa.

This goes particularly badly when the return value is taken as a number of
bytes to copy into, say, a user's buffer for example...

I originally had coded up the fix by creating a return_EIO_<TYPE> macro
for each return type, like this:

static int return_EIO_int(void)
{
    return -EIO;
}
#define EIO_ERROR_INT ((void *) (return_EIO_int))

static struct inode_operations bad_inode_ops =
{
    .create         = EIO_ERROR_INT,
...etc...

but Al felt that it was probably better to create an EIO-returner for each
actual op signature.  Since so few ops share a signature, I just went ahead
& created an EIO function for each individual file & inode op that returns
a value.

Adrian Bunk:
backported to 2.6.16
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

fs/bad_inode.c

@@ -14,61 +14,305 @@
 #include <linux/time.h>
 #include <linux/smp_lock.h>
 #include <linux/namei.h>
+#include <linux/poll.h>
 
-static int return_EIO(void)
+
+static loff_t bad_file_llseek(struct file *file, loff_t offset, int origin)
+{
+	return -EIO;
+}
+
+static ssize_t bad_file_read(struct file *filp, char __user *buf,
+			size_t size, loff_t *ppos)
+{
+        return -EIO;
+}
+
+static ssize_t bad_file_write(struct file *filp, const char __user *buf,
+			size_t siz, loff_t *ppos)
+{
+        return -EIO;
+}
+
+static ssize_t bad_file_aio_read(struct kiocb *iocb, char __user *buf,
+			size_t siz, loff_t pos)
+{
+	return -EIO;
+}
+
+static ssize_t bad_file_aio_write(struct kiocb *iocb, const char __user *buf,
+			size_t siz, loff_t pos)
+{
+	return -EIO;
+}
+
+static int bad_file_readdir(struct file *filp, void *dirent, filldir_t filldir)
+{
+	return -EIO;
+}
+
+static unsigned int bad_file_poll(struct file *filp, poll_table *wait)
+{
+	return POLLERR;
+}
+
+static int bad_file_ioctl (struct inode *inode, struct file *filp,
+			unsigned int cmd, unsigned long arg)
+{
+	return -EIO;
+}
+
+static long bad_file_unlocked_ioctl(struct file *file, unsigned cmd,
+			unsigned long arg)
+{
+	return -EIO;
+}
+
+static long bad_file_compat_ioctl(struct file *file, unsigned int cmd,
+			unsigned long arg)
+{
+	return -EIO;
+}
+
+static int bad_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return -EIO;
+}
+
+static int bad_file_open(struct inode *inode, struct file *filp)
+{
+	return -EIO;
+}
+
+static int bad_file_flush(struct file *file)
+{
+	return -EIO;
+}
+
+static int bad_file_release(struct inode *inode, struct file *filp)
+{
+	return -EIO;
+}
+
+static int bad_file_fsync(struct file *file, struct dentry *dentry,
+			int datasync)
+{
+	return -EIO;
+}
+
+static int bad_file_aio_fsync(struct kiocb *iocb, int datasync)
+{
+	return -EIO;
+}
+
+static int bad_file_fasync(int fd, struct file *filp, int on)
+{
+	return -EIO;
+}
+
+static int bad_file_lock(struct file *file, int cmd, struct file_lock *fl)
+{
+	return -EIO;
+}
+
+static int bad_file_readv(struct file *file, const struct iovec *iv,
+			  unsigned long count, loff_t *pos)
+{
+	return -EIO;
+}
+
+static int bad_file_writev(struct file *file, const struct iovec *iv,
+			   unsigned long count, loff_t *pos)
+{
+	return -EIO;
+}
+
+static ssize_t bad_file_sendfile(struct file *in_file, loff_t *ppos,
+			size_t count, read_actor_t actor, void *target)
+{
+	return -EIO;
+}
+
+static ssize_t bad_file_sendpage(struct file *file, struct page *page,
+			int off, size_t len, loff_t *pos, int more)
 {
 	return -EIO;
 }
 
-#define EIO_ERROR ((void *) (return_EIO))
+static unsigned long bad_file_get_unmapped_area(struct file *file,
+				unsigned long addr, unsigned long len,
+				unsigned long pgoff, unsigned long flags)
+{
+	return -EIO;
+}
+
+static int bad_file_check_flags(int flags)
+{
+	return -EIO;
+}
+
+static int bad_file_dir_notify(struct file *file, unsigned long arg)
+{
+	return -EIO;
+}
+
+static int bad_file_flock(struct file *filp, int cmd, struct file_lock *fl)
+{
+	return -EIO;
+}
 
 static struct file_operations bad_file_ops =
 {
-	.llseek		= EIO_ERROR,
-	.aio_read	= EIO_ERROR,
-	.read		= EIO_ERROR,
-	.write		= EIO_ERROR,
-	.aio_write	= EIO_ERROR,
-	.readdir	= EIO_ERROR,
-	.poll		= EIO_ERROR,
-	.ioctl		= EIO_ERROR,
-	.mmap		= EIO_ERROR,
-	.open		= EIO_ERROR,
-	.flush		= EIO_ERROR,
-	.release	= EIO_ERROR,
-	.fsync		= EIO_ERROR,
-	.aio_fsync	= EIO_ERROR,
-	.fasync		= EIO_ERROR,
-	.lock		= EIO_ERROR,
-	.readv		= EIO_ERROR,
-	.writev		= EIO_ERROR,
-	.sendfile	= EIO_ERROR,
-	.sendpage	= EIO_ERROR,
-	.get_unmapped_area = EIO_ERROR,
+	.llseek		= bad_file_llseek,
+	.read		= bad_file_read,
+	.write		= bad_file_write,
+	.aio_read	= bad_file_aio_read,
+	.aio_write	= bad_file_aio_write,
+	.readdir	= bad_file_readdir,
+	.poll		= bad_file_poll,
+	.ioctl		= bad_file_ioctl,
+	.unlocked_ioctl	= bad_file_unlocked_ioctl,
+	.compat_ioctl	= bad_file_compat_ioctl,
+	.mmap		= bad_file_mmap,
+	.open		= bad_file_open,
+	.flush		= bad_file_flush,
+	.release	= bad_file_release,
+	.fsync		= bad_file_fsync,
+	.aio_fsync	= bad_file_aio_fsync,
+	.fasync		= bad_file_fasync,
+	.lock		= bad_file_lock,
+	.readv		= bad_file_readv,
+	.writev		= bad_file_writev,
+	.sendfile	= bad_file_sendfile,
+	.sendpage	= bad_file_sendpage,
+	.get_unmapped_area = bad_file_get_unmapped_area,
+	.check_flags	= bad_file_check_flags,
+	.dir_notify	= bad_file_dir_notify,
+	.flock		= bad_file_flock,
 };
 
+static int bad_inode_create (struct inode *dir, struct dentry *dentry,
+		int mode, struct nameidata *nd)
+{
+	return -EIO;
+}
+
+static struct dentry *bad_inode_lookup(struct inode *dir,
+			struct dentry *dentry, struct nameidata *nd)
+{
+	return ERR_PTR(-EIO);
+}
+
+static int bad_inode_link (struct dentry *old_dentry, struct inode *dir,
+		struct dentry *dentry)
+{
+	return -EIO;
+}
+
+static int bad_inode_unlink(struct inode *dir, struct dentry *dentry)
+{
+	return -EIO;
+}
+
+static int bad_inode_symlink (struct inode *dir, struct dentry *dentry,
+		const char *symname)
+{
+	return -EIO;
+}
+
+static int bad_inode_mkdir(struct inode *dir, struct dentry *dentry,
+			int mode)
+{
+	return -EIO;
+}
+
+static int bad_inode_rmdir (struct inode *dir, struct dentry *dentry)
+{
+	return -EIO;
+}
+
+static int bad_inode_mknod (struct inode *dir, struct dentry *dentry,
+			int mode, dev_t rdev)
+{
+	return -EIO;
+}
+
+static int bad_inode_rename (struct inode *old_dir, struct dentry *old_dentry,
+		struct inode *new_dir, struct dentry *new_dentry)
+{
+	return -EIO;
+}
+
+static int bad_inode_readlink(struct dentry *dentry, char __user *buffer,
+		int buflen)
+{
+	return -EIO;
+}
+
+static int bad_inode_permission(struct inode *inode, int mask,
+			struct nameidata *nd)
+{
+	return -EIO;
+}
+
+static int bad_inode_getattr(struct vfsmount *mnt, struct dentry *dentry,
+			struct kstat *stat)
+{
+	return -EIO;
+}
+
+static int bad_inode_setattr(struct dentry *direntry, struct iattr *attrs)
+{
+	return -EIO;
+}
+
+static int bad_inode_setxattr(struct dentry *dentry, const char *name,
+		const void *value, size_t size, int flags)
+{
+	return -EIO;
+}
+
+static ssize_t bad_inode_getxattr(struct dentry *dentry, const char *name,
+			void *buffer, size_t size)
+{
+	return -EIO;
+}
+
+static ssize_t bad_inode_listxattr(struct dentry *dentry, char *buffer,
+			size_t buffer_size)
+{
+	return -EIO;
+}
+
+static int bad_inode_removexattr(struct dentry *dentry, const char *name)
+{
+	return -EIO;
+}
+
 static struct inode_operations bad_inode_ops =
 {
-	.create		= EIO_ERROR,
-	.lookup		= EIO_ERROR,
-	.link		= EIO_ERROR,
-	.unlink		= EIO_ERROR,
-	.symlink	= EIO_ERROR,
-	.mkdir		= EIO_ERROR,
-	.rmdir		= EIO_ERROR,
-	.mknod		= EIO_ERROR,
-	.rename		= EIO_ERROR,
-	.readlink	= EIO_ERROR,
+	.create		= bad_inode_create,
+	.lookup		= bad_inode_lookup,
+	.link		= bad_inode_link,
+	.unlink		= bad_inode_unlink,
+	.symlink	= bad_inode_symlink,
+	.mkdir		= bad_inode_mkdir,
+	.rmdir		= bad_inode_rmdir,
+	.mknod		= bad_inode_mknod,
+	.rename		= bad_inode_rename,
+	.readlink	= bad_inode_readlink,
 	/* follow_link must be no-op, otherwise unmounting this inode
 	   won't work */
-	.truncate	= EIO_ERROR,
-	.permission	= EIO_ERROR,
-	.getattr	= EIO_ERROR,
-	.setattr	= EIO_ERROR,
-	.setxattr	= EIO_ERROR,
-	.getxattr	= EIO_ERROR,
-	.listxattr	= EIO_ERROR,
-	.removexattr	= EIO_ERROR,
+	/* put_link returns void */
+	/* truncate returns void */
+	.permission	= bad_inode_permission,
+	.getattr	= bad_inode_getattr,
+	.setattr	= bad_inode_setattr,
+	.setxattr	= bad_inode_setxattr,
+	.getxattr	= bad_inode_getxattr,
+	.listxattr	= bad_inode_listxattr,
+	.removexattr	= bad_inode_removexattr,
+	/* truncate_range returns void */
 };
 
 
@@ -90,7 +334,7 @@ static struct inode_operations bad_inode_ops =
  *	on it to fail from this point on.
  */
  
-void make_bad_inode(struct inode * inode) 
+void make_bad_inode(struct inode *inode)
 {
 	remove_inode_hash(inode);
 
@@ -115,7 +359,7 @@ EXPORT_SYMBOL(make_bad_inode);
  *	Returns true if the inode in question has been marked as bad.
  */
  
-int is_bad_inode(struct inode * inode) 
+int is_bad_inode(struct inode *inode)
 {
 	return (inode->i_op == &bad_inode_ops);	
 }