ksmbd: check if a mount point is crossed during path lookup

Since commit 74d7970febf7 ("ksmbd: fix racy issue from using ->d_parent and
->d_name"), ksmbd can not lookup cross mount points. If last component is
a cross mount point during path lookup, check if it is crossed to follow it
down. And allow path lookup to cross a mount point when a crossmnt
parameter is set to 'yes' in smb.conf.

Cc: stable@vger.kernel.org
Fixes: 74d7970febf7 ("ksmbd: fix racy issue from using ->d_parent and ->d_name")
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 16 insertions, 11 deletions

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index cf8822103f50..ca276634fd58 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -2467,8 +2467,9 @@ static void smb2_update_xattrs(struct ksmbd_tree_connect *tcon,
 	}
 }
 
-static int smb2_creat(struct ksmbd_work *work, struct path *path, char *name,
-		      int open_flags, umode_t posix_mode, bool is_dir)
+static int smb2_creat(struct ksmbd_work *work, struct path *parent_path,
+		      struct path *path, char *name, int open_flags,
+		      umode_t posix_mode, bool is_dir)
 {
 	struct ksmbd_tree_connect *tcon = work->tcon;
 	struct ksmbd_share_config *share = tcon->share_conf;
@@ -2495,7 +2496,7 @@ static int smb2_creat(struct ksmbd_work *work, struct path *path, char *name,
 			return rc;
 	}
 
-	rc = ksmbd_vfs_kern_path_locked(work, name, 0, path, 0);
+	rc = ksmbd_vfs_kern_path_locked(work, name, 0, parent_path, path, 0);
 	if (rc) {
 		pr_err("cannot get linux path (%s), err = %d\n",
 		       name, rc);
@@ -2565,7 +2566,7 @@ int smb2_open(struct ksmbd_work *work)
 	struct ksmbd_tree_connect *tcon = work->tcon;
 	struct smb2_create_req *req;
 	struct smb2_create_rsp *rsp;
-	struct path path;
+	struct path path, parent_path;
 	struct ksmbd_share_config *share = tcon->share_conf;
 	struct ksmbd_file *fp = NULL;
 	struct file *filp = NULL;
@@ -2786,7 +2787,8 @@ int smb2_open(struct ksmbd_work *work)
 		goto err_out1;
 	}
 
-	rc = ksmbd_vfs_kern_path_locked(work, name, LOOKUP_NO_SYMLINKS, &path, 1);
+	rc = ksmbd_vfs_kern_path_locked(work, name, LOOKUP_NO_SYMLINKS,
+					&parent_path, &path, 1);
 	if (!rc) {
 		file_present = true;
 
@@ -2906,7 +2908,8 @@ int smb2_open(struct ksmbd_work *work)
 
 	/*create file if not present */
 	if (!file_present) {
-		rc = smb2_creat(work, &path, name, open_flags, posix_mode,
+		rc = smb2_creat(work, &parent_path, &path, name, open_flags,
+				posix_mode,
 				req->CreateOptions & FILE_DIRECTORY_FILE_LE);
 		if (rc) {
 			if (rc == -ENOENT) {
@@ -3321,8 +3324,9 @@ int smb2_open(struct ksmbd_work *work)
 
 err_out:
 	if (file_present || created) {
-		inode_unlock(d_inode(path.dentry->d_parent));
-		dput(path.dentry);
+		inode_unlock(d_inode(parent_path.dentry));
+		path_put(&path);
+		path_put(&parent_path);
 	}
 	ksmbd_revert_fsids(work);
 err_out1:
@@ -5545,7 +5549,7 @@ static int smb2_create_link(struct ksmbd_work *work,
 			    struct nls_table *local_nls)
 {
 	char *link_name = NULL, *target_name = NULL, *pathname = NULL;
-	struct path path;
+	struct path path, parent_path;
 	bool file_present = false;
 	int rc;
 
@@ -5575,7 +5579,7 @@ static int smb2_create_link(struct ksmbd_work *work,
 
 	ksmbd_debug(SMB, "target name is %s\n", target_name);
 	rc = ksmbd_vfs_kern_path_locked(work, link_name, LOOKUP_NO_SYMLINKS,
-					&path, 0);
+					&parent_path, &path, 0);
 	if (rc) {
 		if (rc != -ENOENT)
 			goto out;
@@ -5605,8 +5609,9 @@ static int smb2_create_link(struct ksmbd_work *work,
 		rc = -EINVAL;
 out:
 	if (file_present) {
-		inode_unlock(d_inode(path.dentry->d_parent));
+		inode_unlock(d_inode(parent_path.dentry));
 		path_put(&path);
+		path_put(&parent_path);
 	}
 	if (!IS_ERR(link_name))
 		kfree(link_name);