[PATCH] ovl: restrict casefold consistency checks to directories

[Hungyu Lin]

ovl_lookup_single() compares every positive child's casefold flag with
that of the overlay. On casefolded ext4, regular files do not inherit
the casefold flag from their parent directory. Looking up an existing
regular file on a casefolded overlay therefore fails with EREMOTE.
Symlinks, FIFOs and whiteouts are rejected by the same check.

Restrict the child consistency check to directories, along with the
corresponding assertion in ovl_get_inode(). This allows nondirectory
objects to be looked up without rejecting them or warning about their
flags, while directories with inconsistent casefold settings are still
rejected.

Fixes: 16754d61dc69 ("ovl: Support mounting case-insensitive enabled layers")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hungyu Lin <dennylin0707@xxxxxxxxx>
---
 fs/overlayfs/inode.c | 2 +-
 fs/overlayfs/namei.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 63906b3dafcb..4428c50c3185 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -1278,7 +1278,7 @@ struct inode *ovl_get_inode(struct super_block *sb,
 	}
 	ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
 	ovl_inode_init(inode, oip, ino, fsid);
-	WARN_ON_ONCE(!!IS_CASEFOLDED(inode) != ofs->casefold);
+	WARN_ON_ONCE(is_dir && !!IS_CASEFOLDED(inode) != ofs->casefold);
 
 	if (upperdentry && ovl_is_impuredir(sb, upperdentry))
 		ovl_set_flag(OVL_IMPURE, inode);
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index ca899fdfaafd..023966d89f74 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -266,7 +266,7 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
 		goto out_err;
 	}
 
-	if (ofs->casefold != ovl_dentry_casefolded(this)) {
+	if (d_is_dir(this) && ofs->casefold != ovl_dentry_casefolded(this)) {
 		warn = "child wrong casefold";
 		err = -EREMOTE;
 		goto out_warn;
-- 
2.43.0