From: Erez Zadok <ezk@xxxxxxxxxxxxx>
We have to read-lock the superblock rwsem, and we have to revalidate the
parent dentry and this one. A branch-management operation could have taken
place, mid-way through a VFS operation that eventually reaches
unionfs_create(). So we have to ensure consistency, just as we do with the
file operations.
Signed-off-by: Erez Zadok <ezk@xxxxxxxxxxxxx>
Signed-off-by: Josef 'Jeff' Sipek <jsipek@xxxxxxxxxxxxx>
---
fs/unionfs/inode.c | 29 ++++++++++++++++++++++++++++-
1 files changed, 28 insertions(+), 1 deletions(-)
diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
index 6dfc16f..edd226f 100644
--- a/fs/unionfs/inode.c
+++ b/fs/unionfs/inode.c
@@ -28,9 +28,35 @@ static int unionfs_create(struct inode *parent, struct dentry *dentry,
struct dentry *hidden_parent_dentry = NULL;
int bindex = 0, bstart;
char *name = NULL;
-
+ int valid = 0;
+
+ /*
+ * We have to read-lock the superblock rwsem, and we have to
+ * revalidate the parent dentry and this one. A branch-management
+ * operation could have taken place, mid-way through a VFS operation
+ * that eventually reaches here. So we have to ensure consistency,
+ * just as we do with the file operations.
+ *
+ * XXX: we may need to do this for all other inode ops that take a
+ * dentry.
+ */
+ unionfs_read_lock(dentry->d_sb);
unionfs_lock_dentry(dentry);
+ unionfs_lock_dentry(dentry->d_parent);
+ valid = __unionfs_d_revalidate_chain(dentry->d_parent, nd);
+ unionfs_unlock_dentry(dentry->d_parent);
+ if (!valid) {
+ err = -ENOENT; /* same as what real_lookup does */
+ goto out;
+ }
+ valid = __unionfs_d_revalidate_chain(dentry, nd);
+ /*
+ * It's only a bug if this dentry was not negative and couldn't be
+ * revalidated (shouldn't happen).
+ */
+ BUG_ON(!valid && dentry->d_inode);
+
/* We start out in the leftmost branch. */
bstart = dbstart(dentry);
hidden_dentry = unionfs_lower_dentry(dentry);
@@ -184,6 +210,7 @@ out:
kfree(name);
unionfs_unlock_dentry(dentry);
+ unionfs_read_unlock(dentry->d_sb);
return err;
}
--
1.5.0.3.268.g3dda
-
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