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Commit 75a2352d authored by J. Bruce Fields's avatar J. Bruce Fields Committed by Al Viro
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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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3f70bd51

fs/dcache.c

+6 −1
Original line number Diff line number Diff line
@@ -2676,9 +2676,14 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) 
		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 */