afs: Add missing vnode validation checks

afs_d_revalidate() should only be validating the directory entry it is
given and the directory to which that belongs; it shouldn't be validating
the inode/vnode to which that dentry points.  Besides, validation need to
be done even if we don't call afs_d_revalidate() - which might be the case
if we're starting from a file descriptor.

In order for afs_d_revalidate() to be fixed, validation points must be
added in some other places.  Certain directory operations, such as
afs_unlink(), already check this, but not all and not all file operations
either.

Note that the validation of a vnode not only checks to see if the
attributes we have are correct, but also gets a promise from the server to
notify us if that file gets changed by a third party.

Add the following checks:

 - Check the vnode we're going to make a hard link to.
 - Check the vnode we're going to move/rename.
 - Check the vnode we're going to read from.
 - Check the vnode we're going to write to.
 - Check the vnode we're going to sync.
 - Check the vnode we're going to make a mapped page writable for.

Some of these aren't strictly necessary as we're going to perform a server
operation that might get the attributes anyway from which we can determine
if something changed - though it might not get us a callback promise.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Markus Suvanto <markus.suvanto@gmail.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/163111667354.283156.12720698333342917516.stgit@warthog.procyon.org.uk/

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index ac829e63c570..a8e3ae55f1f9 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -1792,6 +1792,10 @@ static int afs_link(struct dentry *from, struct inode *dir,
 		goto error;
 	}
 
+	ret = afs_validate(vnode, op->key);
+	if (ret < 0)
+		goto error_op;
+
 	afs_op_set_vnode(op, 0, dvnode);
 	afs_op_set_vnode(op, 1, vnode);
 	op->file[0].dv_delta = 1;
@@ -1805,6 +1809,8 @@ static int afs_link(struct dentry *from, struct inode *dir,
 	op->create.reason	= afs_edit_dir_for_link;
 	return afs_do_sync_operation(op);
 
+error_op:
+	afs_put_operation(op);
 error:
 	d_drop(dentry);
 	_leave(" = %d", ret);
@@ -1989,6 +1995,11 @@ static int afs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 	if (IS_ERR(op))
 		return PTR_ERR(op);
 
+	ret = afs_validate(vnode, op->key);
+	op->error = ret;
+	if (ret < 0)
+		goto error;
+
 	afs_op_set_vnode(op, 0, orig_dvnode);
 	afs_op_set_vnode(op, 1, new_dvnode); /* May be same as orig_dvnode */
 	op->file[0].dv_delta = 1;