ksmbd: use LOOKUP_BENEATH to prevent the out of share access

instead of removing '..' in a given path, call
kern_path with LOOKUP_BENEATH flag to prevent
the out of share access.

ran various test on this:
smb2-cat-async smb://127.0.0.1/homes/../out_of_share
smb2-cat-async smb://127.0.0.1/homes/foo/../../out_of_share
smbclient //127.0.0.1/homes -c "mkdir ../foo2"
smbclient //127.0.0.1/homes -c "rename bar ../bar"

Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Boehme <slow@samba.org>
Tested-by: Steve French <smfrench@gmail.com>
Tested-by: Namjae Jeon <linkinjeon@kernel.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 82 insertions, 74 deletions

diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c
index 3733e4944c1d..b41954294d38 100644
--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -19,6 +19,8 @@
 #include <linux/sched/xacct.h>
 #include <linux/crc32c.h>
 
+#include "../internal.h"	/* for vfs_path_lookup */
+
 #include "glob.h"
 #include "oplock.h"
 #include "connection.h"
@@ -44,7 +46,6 @@ static char *extract_last_component(char *path)
 		p++;
 	} else {
 		p = NULL;
-		pr_err("Invalid path %s\n", path);
 	}
 	return p;
 }
@@ -155,7 +156,7 @@ int ksmbd_vfs_query_maximal_access(struct user_namespace *user_ns,
 /**
  * ksmbd_vfs_create() - vfs helper for smb create file
  * @work:	work
- * @name:	file name
+ * @name:	file name that is relative to share
  * @mode:	file create mode
  *
  * Return:	0 on success, otherwise error
@@ -166,7 +167,8 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
 	struct dentry *dentry;
 	int err;
 
-	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_NO_SYMLINKS);
+	dentry = ksmbd_vfs_kern_path_create(work, name,
+					    LOOKUP_NO_SYMLINKS, &path);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		if (err != -ENOENT)
@@ -191,7 +193,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
 /**
  * ksmbd_vfs_mkdir() - vfs helper for smb create directory
  * @work:	work
- * @name:	directory name
+ * @name:	directory name that is relative to share
  * @mode:	directory create mode
  *
  * Return:	0 on success, otherwise error
@@ -203,8 +205,9 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
 	struct dentry *dentry;
 	int err;
 
-	dentry = kern_path_create(AT_FDCWD, name, &path,
-				  LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY);
+	dentry = ksmbd_vfs_kern_path_create(work, name,
+					    LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY,
+					    &path);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		if (err != -EEXIST)
@@ -579,7 +582,7 @@ int ksmbd_vfs_fsync(struct ksmbd_work *work, u64 fid, u64 p_id)
 
 /**
  * ksmbd_vfs_remove_file() - vfs helper for smb rmdir or unlink
- * @name:	absolute directory or file name
+ * @name:	directory or file name that is relative to share
  *
  * Return:	0 on success, otherwise error
  */
@@ -593,7 +596,7 @@ int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name)
 	if (ksmbd_override_fsids(work))
 		return -ENOMEM;
 
-	err = kern_path(name, LOOKUP_NO_SYMLINKS, &path);
+	err = ksmbd_vfs_kern_path(work, name, LOOKUP_NO_SYMLINKS, &path, false);
 	if (err) {
 		ksmbd_debug(VFS, "can't get %s, err %d\n", name, err);
 		ksmbd_revert_fsids(work);
@@ -638,7 +641,7 @@ out_err:
 /**
  * ksmbd_vfs_link() - vfs helper for creating smb hardlink
  * @oldname:	source file name
- * @newname:	hardlink name
+ * @newname:	hardlink name that is relative to share
  *
  * Return:	0 on success, otherwise error
  */
@@ -659,8 +662,9 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
 		goto out1;
 	}
 
-	dentry = kern_path_create(AT_FDCWD, newname, &newpath,
-				  LOOKUP_NO_SYMLINKS | LOOKUP_REVAL);
+	dentry = ksmbd_vfs_kern_path_create(work, newname,
+					    LOOKUP_NO_SYMLINKS | LOOKUP_REVAL,
+					    &newpath);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		pr_err("path create err for %s, err %d\n", newname, err);
@@ -781,14 +785,17 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
 	int err;
 
 	dst_name = extract_last_component(newname);
-	if (!dst_name)
-		return -EINVAL;
+	if (!dst_name) {
+		dst_name = newname;
+		newname = "";
+	}
 
 	src_dent_parent = dget_parent(fp->filp->f_path.dentry);
 	src_dent = fp->filp->f_path.dentry;
 
-	err = kern_path(newname, LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY,
-			&dst_path);
+	err = ksmbd_vfs_kern_path(work, newname,
+				  LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY,
+				  &dst_path, false);
 	if (err) {
 		ksmbd_debug(VFS, "Cannot get path for %s [%d]\n", newname, err);
 		goto out;
@@ -834,61 +841,43 @@ out:
 /**
  * ksmbd_vfs_truncate() - vfs helper for smb file truncate
  * @work:	work
- * @name:	old filename
  * @fid:	file id of old file
  * @size:	truncate to given size
  *
  * Return:	0 on success, otherwise error
  */
-int ksmbd_vfs_truncate(struct ksmbd_work *work, const char *name,
+int ksmbd_vfs_truncate(struct ksmbd_work *work,
 		       struct ksmbd_file *fp, loff_t size)
 {
-	struct path path;
 	int err = 0;
+	struct file *filp;
 
-	if (name) {
-		err = kern_path(name, LOOKUP_NO_SYMLINKS, &path);
-		if (err) {
-			pr_err("cannot get linux path for %s, err %d\n",
-			       name, err);
-			return err;
-		}
-		err = vfs_truncate(&path, size);
-		if (err)
-			pr_err("truncate failed for %s err %d\n",
-			       name, err);
-		path_put(&path);
-	} else {
-		struct file *filp;
-
-		filp = fp->filp;
-
-		/* Do we need to break any of a levelII oplock? */
-		smb_break_all_levII_oplock(work, fp, 1);
+	filp = fp->filp;
 
-		if (!work->tcon->posix_extensions) {
-			struct inode *inode = file_inode(filp);
+	/* Do we need to break any of a levelII oplock? */
+	smb_break_all_levII_oplock(work, fp, 1);
 
-			if (size < inode->i_size) {
-				err = check_lock_range(filp, size,
-						       inode->i_size - 1, WRITE);
-			} else {
-				err = check_lock_range(filp, inode->i_size,
-						       size - 1, WRITE);
-			}
+	if (!work->tcon->posix_extensions) {
+		struct inode *inode = file_inode(filp);
 
-			if (err) {
-				pr_err("failed due to lock\n");
-				return -EAGAIN;
-			}
+		if (size < inode->i_size) {
+			err = check_lock_range(filp, size,
+					       inode->i_size - 1, WRITE);
+		} else {
+			err = check_lock_range(filp, inode->i_size,
+					       size - 1, WRITE);
 		}
 
-		err = vfs_truncate(&filp->f_path, size);
-		if (err)
-			pr_err("truncate failed for filename : %s err %d\n",
-			       fp->filename, err);
+		if (err) {
+			pr_err("failed due to lock\n");
+			return -EAGAIN;
+		}
 	}
 
+	err = vfs_truncate(&filp->f_path, size);
+	if (err)
+		pr_err("truncate failed for filename : %s err %d\n",
+		       fp->filename, err);
 	return err;
 }
 
@@ -1206,22 +1195,25 @@ static int ksmbd_vfs_lookup_in_dir(struct path *dir, char *name, size_t namelen)
 
 /**
  * ksmbd_vfs_kern_path() - lookup a file and get path info
- * @name:	name of file for lookup
+ * @name:	file path that is relative to share
  * @flags:	lookup flags
  * @path:	if lookup succeed, return path info
  * @caseless:	caseless filename lookup
  *
  * Return:	0 on success, otherwise error
  */
-int ksmbd_vfs_kern_path(char *name, unsigned int flags, struct path *path,
-			bool caseless)
+int ksmbd_vfs_kern_path(struct ksmbd_work *work, char *name,
+			unsigned int flags, struct path *path, bool caseless)
 {
+	struct ksmbd_share_config *share_conf = work->tcon->share_conf;
 	int err;
 
-	if (name[0] != '/')
-		return -EINVAL;
-
-	err = kern_path(name, flags, path);
+	flags |= LOOKUP_BENEATH;
+	err = vfs_path_lookup(share_conf->vfs_path.dentry,
+			      share_conf->vfs_path.mnt,
+			      name,
+			      flags,
+			      path);
 	if (!err)
 		return 0;
 
@@ -1235,11 +1227,10 @@ int ksmbd_vfs_kern_path(char *name, unsigned int flags, struct path *path,
 			return -ENOMEM;
 
 		path_len = strlen(filepath);
-		remain_len = path_len - 1;
+		remain_len = path_len;
 
-		err = kern_path("/", flags, &parent);
-		if (err)
-			goto out;
+		parent = share_conf->vfs_path;
+		path_get(&parent);
 
 		while (d_can_lookup(parent.dentry)) {
 			char *filename = filepath + path_len - remain_len;
@@ -1252,21 +1243,21 @@ int ksmbd_vfs_kern_path(char *name, unsigned int flags, struct path *path,
 
 			err = ksmbd_vfs_lookup_in_dir(&parent, filename,
 						      filename_len);
-			if (err) {
-				path_put(&parent);
+			path_put(&parent);
+			if (err)
 				goto out;
-			}
 
-			path_put(&parent);
 			next[0] = '\0';
 
-			err = kern_path(filepath, flags, &parent);
+			err = vfs_path_lookup(share_conf->vfs_path.dentry,
+					      share_conf->vfs_path.mnt,
+					      filepath,
+					      flags,
+					      &parent);
 			if (err)
 				goto out;
-
-			if (is_last) {
-				path->mnt = parent.mnt;
-				path->dentry = parent.dentry;
+			else if (is_last) {
+				*path = parent;
 				goto out;
 			}
 
@@ -1282,6 +1273,23 @@ out:
 	return err;
 }
 
+struct dentry *ksmbd_vfs_kern_path_create(struct ksmbd_work *work,
+					  const char *name,
+					  unsigned int flags,
+					  struct path *path)
+{
+	char *abs_name;
+	struct dentry *dent;
+
+	abs_name = convert_to_unix_name(work->tcon->share_conf, name);
+	if (!abs_name)
+		return ERR_PTR(-ENOMEM);
+
+	dent = kern_path_create(AT_FDCWD, abs_name, path, flags);
+	kfree(abs_name);
+	return dent;
+}
+
 int ksmbd_vfs_remove_acl_xattrs(struct user_namespace *user_ns,
 				struct dentry *dentry)
 {