From 333111a6dc32a2768f581876bdb5ef4231f5084e Mon Sep 17 00:00:00 2001 From: Hyunchul Lee Date: Wed, 23 Jun 2021 11:07:43 +0900 Subject: [PATCH] ksmbd: factor out a ksmbd_vfs_lock_parent helper Factor out a self-contained helper to get stable parent dentry. Signed-off-by: Hyunchul Lee Signed-off-by: Namjae Jeon Signed-off-by: Steve French --- fs/ksmbd/vfs.c | 125 ++++++++++++++++++++++++++++----------------------------- 1 file changed, 62 insertions(+), 63 deletions(-) diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c index fddabb4..e64eab7 100644 --- a/fs/ksmbd/vfs.c +++ b/fs/ksmbd/vfs.c @@ -60,6 +60,41 @@ static void ksmbd_vfs_inherit_owner(struct ksmbd_work *work, i_uid_write(inode, i_uid_read(parent_inode)); } +/** + * ksmbd_vfs_lock_parent() - lock parent dentry if it is stable + * + * the parent dentry got by dget_parent or @parent could be + * unstable, we try to lock a parent inode and lookup the + * child dentry again. + * + * the reference count of @parent isn't incremented. + */ +static int ksmbd_vfs_lock_parent(struct dentry *parent, struct dentry *child) +{ + struct dentry *dentry; + int ret = 0; + + inode_lock_nested(d_inode(parent), I_MUTEX_PARENT); + dentry = lookup_one_len(child->d_name.name, parent, + child->d_name.len); + if (IS_ERR(dentry)) { + ret = PTR_ERR(dentry); + goto out_err; + } + + if (dentry != child) { + ret = -ESTALE; + dput(dentry); + goto out_err; + } + + dput(dentry); + return 0; +out_err: + inode_unlock(d_inode(parent)); + return ret; +} + int ksmbd_vfs_inode_permission(struct dentry *dentry, int acc_mode, bool delete) { int mask, ret = 0; @@ -78,29 +113,18 @@ int ksmbd_vfs_inode_permission(struct dentry *dentry, int acc_mode, bool delete) return -EACCES; if (delete) { - struct dentry *child, *parent; + struct dentry *parent; parent = dget_parent(dentry); - inode_lock_nested(d_inode(parent), I_MUTEX_PARENT); - child = lookup_one_len(dentry->d_name.name, parent, - dentry->d_name.len); - if (IS_ERR(child)) { - ret = PTR_ERR(child); - goto out_lock; - } - - if (child != dentry) { - ret = -ESTALE; - dput(child); - goto out_lock; + ret = ksmbd_vfs_lock_parent(parent, dentry); + if (ret) { + dput(parent); + return ret; } - dput(child); - if (inode_permission(&init_user_ns, d_inode(parent), MAY_EXEC | MAY_WRITE)) { + if (inode_permission(&init_user_ns, d_inode(parent), MAY_EXEC | MAY_WRITE)) ret = -EACCES; - goto out_lock; - } -out_lock: + inode_unlock(d_inode(parent)); dput(parent); } @@ -109,7 +133,7 @@ out_lock: int ksmbd_vfs_query_maximal_access(struct dentry *dentry, __le32 *daccess) { - struct dentry *parent, *child; + struct dentry *parent; int ret = 0; *daccess = cpu_to_le32(FILE_READ_ATTRIBUTES | READ_CONTROL); @@ -127,25 +151,15 @@ int ksmbd_vfs_query_maximal_access(struct dentry *dentry, __le32 *daccess) *daccess |= FILE_EXECUTE_LE; parent = dget_parent(dentry); - inode_lock_nested(d_inode(parent), I_MUTEX_PARENT); - child = lookup_one_len(dentry->d_name.name, parent, - dentry->d_name.len); - if (IS_ERR(child)) { - ret = PTR_ERR(child); - goto out_lock; - } - - if (child != dentry) { - ret = -ESTALE; - dput(child); - goto out_lock; + ret = ksmbd_vfs_lock_parent(parent, dentry); + if (ret) { + dput(parent); + return ret; } - dput(child); if (!inode_permission(&init_user_ns, d_inode(parent), MAY_EXEC | MAY_WRITE)) *daccess |= FILE_DELETE_LE; -out_lock: inode_unlock(d_inode(parent)); dput(parent); return ret; @@ -573,7 +587,7 @@ int ksmbd_vfs_fsync(struct ksmbd_work *work, u64 fid, u64 p_id) int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name) { struct path path; - struct dentry *dentry, *parent; + struct dentry *parent; int err; int flags = 0; @@ -592,35 +606,32 @@ int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name) } parent = dget_parent(path.dentry); - inode_lock_nested(d_inode(parent), I_MUTEX_PARENT); - dentry = lookup_one_len(path.dentry->d_name.name, parent, - strlen(path.dentry->d_name.name)); - if (IS_ERR(dentry)) { - err = PTR_ERR(dentry); - ksmbd_debug(VFS, "%s: lookup failed, err %d\n", - path.dentry->d_name.name, err); - goto out_err; + err = ksmbd_vfs_lock_parent(parent, path.dentry); + if (err) { + dput(parent); + path_put(&path); + ksmbd_revert_fsids(work); + return err; } - if (!d_inode(dentry) || !d_inode(dentry)->i_nlink) { - dput(dentry); + if (!d_inode(path.dentry)->i_nlink) { err = -ENOENT; goto out_err; } - if (S_ISDIR(d_inode(dentry)->i_mode)) { - err = vfs_rmdir(&init_user_ns, d_inode(parent), dentry); + if (S_ISDIR(d_inode(path.dentry)->i_mode)) { + err = vfs_rmdir(&init_user_ns, d_inode(parent), path.dentry); if (err && err != -ENOTEMPTY) ksmbd_debug(VFS, "%s: rmdir failed, err %d\n", name, err); } else { - err = vfs_unlink(&init_user_ns, d_inode(parent), dentry, NULL); + err = vfs_unlink(&init_user_ns, d_inode(parent), path.dentry, + NULL); if (err) ksmbd_debug(VFS, "%s: unlink failed, err %d\n", name, err); } - dput(dentry); out_err: inode_unlock(d_inode(parent)); dput(parent); @@ -1086,30 +1097,18 @@ int ksmbd_vfs_remove_xattr(struct dentry *dentry, char *attr_name) int ksmbd_vfs_unlink(struct dentry *dir, struct dentry *dentry) { - struct dentry *child; int err = 0; - inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); + err = ksmbd_vfs_lock_parent(dir, dentry); + if (err) + return err; dget(dentry); - child = lookup_one_len(dentry->d_name.name, dir, dentry->d_name.len); - if (IS_ERR(child)) { - err = PTR_ERR(child); - goto out; - } - - if (child != dentry) { - err = -ESTALE; - dput(child); - goto out; - } - dput(child); if (S_ISDIR(d_inode(dentry)->i_mode)) err = vfs_rmdir(&init_user_ns, d_inode(dir), dentry); else err = vfs_unlink(&init_user_ns, d_inode(dir), dentry, NULL); -out: dput(dentry); inode_unlock(d_inode(dir)); if (err) -- 2.7.4