dcache: close d_move race in d_splice_alias
d_splice_alias will d_move an IS_ROOT() directory dentry into place if
one exists. This should be safe as long as the dentry remains IS_ROOT,
but I can't see what guarantees that: once we drop the i_lock all we
hold here is the i_mutex on an unrelated parent directory.
Instead copy the logic of d_materialise_unique.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index 8bdae36..8c09db9 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2676,9 +2676,14 @@
new = __d_find_alias(inode, 1);
if (new) {
BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
+ write_seqlock(&rename_lock);
+ __d_materialise_dentry(dentry, new);
+ write_sequnlock(&rename_lock);
+ __d_drop(new);
+ _d_rehash(new);
+ spin_unlock(&new->d_lock);
spin_unlock(&inode->i_lock);
security_d_instantiate(new, inode);
- d_move(new, dentry);
iput(inode);
} else {
/* already taking inode->i_lock, so d_add() by hand */