[PATCH v8 5/6] xfs: sanity check inode mode when creating new dentry

[Amir Goldstein <amir73il@gmail.com>]

The helper xfs_dentry_to_name() is used by 2 different
classes of callers: Callers that pass zero mode and don't care
about the returned name.type field and Callers that pass
non zero mode and do care about the name.type field.

Change xfs_dentry_to_name() to not take the mode argument and
change the call sites of the first class to not pass the mode
argument.

Create a new helper xfs_dentry_mode_to_name() which does pass
the mode argument and returns -EFSCORRUPTED if mode is invalid.
Callers that translate non zero mode to on-disk file type now
check the return value and will export the error to user instead
of staging an invalid file type to be written to directory entry.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/xfs/xfs_iops.c | 48 +++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 821f08d..22c1615 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -98,12 +98,27 @@ xfs_init_security(
 static void
 xfs_dentry_to_name(
 	struct xfs_name	*namep,
+	struct dentry	*dentry)
+{
+	namep->name = dentry->d_name.name;
+	namep->len = dentry->d_name.len;
+	namep->type = XFS_DIR3_FT_UNKNOWN;
+}
+
+static int
+xfs_dentry_mode_to_name(
+	struct xfs_name	*namep,
 	struct dentry	*dentry,
 	int		mode)
 {
 	namep->name = dentry->d_name.name;
 	namep->len = dentry->d_name.len;
 	namep->type = xfs_mode_to_ftype(mode);
+
+	if (unlikely(namep->type == XFS_DIR3_FT_UNKNOWN))
+		return -EFSCORRUPTED;
+
+	return 0;
 }
 
 STATIC void
@@ -119,7 +134,7 @@ xfs_cleanup_inode(
 	 * xfs_init_security we must back out.
 	 * ENOSPC can hit here, among other things.
 	 */
-	xfs_dentry_to_name(&teardown, dentry, 0);
+	xfs_dentry_to_name(&teardown, dentry);
 
 	xfs_remove(XFS_I(dir), &teardown, XFS_I(inode));
 }
@@ -154,8 +169,12 @@ xfs_generic_create(
 	if (error)
 		return error;
 
+	/* Verify mode is valid also for tmpfile case */
+	error = xfs_dentry_mode_to_name(&name, dentry, mode);
+	if (unlikely(error))
+		goto out_free_acl;
+
 	if (!tmpfile) {
-		xfs_dentry_to_name(&name, dentry, mode);
 		error = xfs_create(XFS_I(dir), &name, mode, rdev, &ip);
 	} else {
 		error = xfs_create_tmpfile(XFS_I(dir), dentry, mode, &ip);
@@ -248,7 +267,7 @@ xfs_vn_lookup(
 	if (dentry->d_name.len >= MAXNAMELEN)
 		return ERR_PTR(-ENAMETOOLONG);
 
-	xfs_dentry_to_name(&name, dentry, 0);
+	xfs_dentry_to_name(&name, dentry);
 	error = xfs_lookup(XFS_I(dir), &name, &cip, NULL);
 	if (unlikely(error)) {
 		if (unlikely(error != -ENOENT))
@@ -275,7 +294,7 @@ xfs_vn_ci_lookup(
 	if (dentry->d_name.len >= MAXNAMELEN)
 		return ERR_PTR(-ENAMETOOLONG);
 
-	xfs_dentry_to_name(&xname, dentry, 0);
+	xfs_dentry_to_name(&xname, dentry);
 	error = xfs_lookup(XFS_I(dir), &xname, &ip, &ci_name);
 	if (unlikely(error)) {
 		if (unlikely(error != -ENOENT))
@@ -310,7 +329,9 @@ xfs_vn_link(
 	struct xfs_name	name;
 	int		error;
 
-	xfs_dentry_to_name(&name, dentry, inode->i_mode);
+	error = xfs_dentry_mode_to_name(&name, dentry, inode->i_mode);
+	if (unlikely(error))
+		return error;
 
 	error = xfs_link(XFS_I(dir), XFS_I(inode), &name);
 	if (unlikely(error))
@@ -329,7 +350,7 @@ xfs_vn_unlink(
 	struct xfs_name	name;
 	int		error;
 
-	xfs_dentry_to_name(&name, dentry, 0);
+	xfs_dentry_to_name(&name, dentry);
 
 	error = xfs_remove(XFS_I(dir), &name, XFS_I(d_inode(dentry)));
 	if (error)
@@ -359,7 +380,9 @@ xfs_vn_symlink(
 
 	mode = S_IFLNK |
 		(irix_symlink_mode ? 0777 & ~current_umask() : S_IRWXUGO);
-	xfs_dentry_to_name(&name, dentry, mode);
+	error = xfs_dentry_mode_to_name(&name, dentry, mode);
+	if (unlikely(error))
+		goto out;
 
 	error = xfs_symlink(XFS_I(dir), &name, symname, mode, &cip);
 	if (unlikely(error))
@@ -395,6 +418,7 @@ xfs_vn_rename(
 {
 	struct inode	*new_inode = d_inode(ndentry);
 	int		omode = 0;
+	int		error;
 	struct xfs_name	oname;
 	struct xfs_name	nname;
 
@@ -405,8 +429,14 @@ xfs_vn_rename(
 	if (flags & RENAME_EXCHANGE)
 		omode = d_inode(ndentry)->i_mode;
 
-	xfs_dentry_to_name(&oname, odentry, omode);
-	xfs_dentry_to_name(&nname, ndentry, d_inode(odentry)->i_mode);
+	error = xfs_dentry_mode_to_name(&oname, odentry, omode);
+	if (omode && unlikely(error))
+		return error;
+
+	error = xfs_dentry_mode_to_name(&nname, ndentry,
+					d_inode(odentry)->i_mode);
+	if (unlikely(error))
+		return error;
 
 	return xfs_rename(XFS_I(odir), &oname, XFS_I(d_inode(odentry)),
 			  XFS_I(ndir), &nname,
-- 
2.7.4