[PATCH] bad_inode: add missing i_op initializers

[PATCH] bad_inode: add missing i_op initializers

[Miklos Szeredi]

New inode operations were forgotten to be added to bad_inode.  Most of the
time the op is checked for NULL before being called but marking the inode
bad and the check can race (very unlikely).

However in case of ->get_link() only DCACHE_SYMLINK_TYPE is checked before
calling the op, so there's no race and will definitely oops when trying to
follow links on such a beast.

Also remove comments about extinct ops.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
---
 fs/bad_inode.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 51 insertions(+), 4 deletions(-)

diff --git a/fs/bad_inode.c b/fs/bad_inode.c
index 8712062275b8..5f685c819298 100644
--- a/fs/bad_inode.c
+++ b/fs/bad_inode.c
@@ -106,6 +106,50 @@ static ssize_t bad_inode_listxattr(struct dentry *dentry, char *buffer,
 	return -EIO;
 }
 
+static const char *bad_inode_get_link(struct dentry *dentry,
+				      struct inode *inode,
+				      struct delayed_call *done)
+{
+	return ERR_PTR(-EIO);
+}
+
+static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type)
+{
+	return ERR_PTR(-EIO);
+}
+
+static int bad_inode_fiemap(struct inode *inode,
+			    struct fiemap_extent_info *fieinfo, u64 start,
+			    u64 len)
+{
+	return -EIO;
+}
+
+static int bad_inode_update_time(struct inode *inode, struct timespec *time,
+				 int flags)
+{
+	return -EIO;
+}
+
+static int bad_inode_atomic_open(struct inode *inode, struct dentry *dentry,
+				 struct file *file, unsigned int open_flag,
+				 umode_t create_mode, int *opened)
+{
+	return -EIO;
+}
+
+static int bad_inode_tmpfile(struct inode *inode, struct dentry *dentry,
+			     umode_t mode)
+{
+	return -EIO;
+}
+
+static int bad_inode_set_acl(struct inode *inode, struct posix_acl *acl,
+			     int type)
+{
+	return -EIO;
+}
+
 static const struct inode_operations bad_inode_ops =
 {
 	.create		= bad_inode_create,
@@ -118,14 +162,17 @@ static const struct inode_operations bad_inode_ops =
 	.mknod		= bad_inode_mknod,
 	.rename		= bad_inode_rename2,
 	.readlink	= bad_inode_readlink,
-	/* follow_link must be no-op, otherwise unmounting this inode
-	   won't work */
-	/* put_link returns void */
-	/* truncate returns void */
 	.permission	= bad_inode_permission,
 	.getattr	= bad_inode_getattr,
 	.setattr	= bad_inode_setattr,
 	.listxattr	= bad_inode_listxattr,
+	.get_link	= bad_inode_get_link,
+	.get_acl	= bad_inode_get_acl,
+	.fiemap		= bad_inode_fiemap,
+	.update_time	= bad_inode_update_time,
+	.atomic_open	= bad_inode_atomic_open,
+	.tmpfile	= bad_inode_tmpfile,
+	.set_acl	= bad_inode_set_acl,
 };
 
 
-- 
2.5.5

Re: [PATCH] bad_inode: add missing i_op initializers

[Christoph Hellwig]

On Mon, Nov 07, 2016 at 10:16:21AM +0100, Miklos Szeredi wrote:
> New inode operations were forgotten to be added to bad_inode.  Most of the
> time the op is checked for NULL before being called but marking the inode
> bad and the check can race (very unlikely).
> 
> However in case of ->get_link() only DCACHE_SYMLINK_TYPE is checked before
> calling the op, so there's no race and will definitely oops when trying to
> follow links on such a beast.
> 
> Also remove comments about extinct ops.

Can someone come up with some BUILD_BUG_ON magic to catch issues like
this?