From: André Almeida <andrealmeid@igalia.com>
Date: Thu, 14 Aug 2025 17:22:19 +0000 (-0300)
Subject: ovl: Check for casefold consistency when creating new dentries
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=dfc7da402ccc92d6e4b01a4778a3f15f2496b9af;p=users%2Fhch%2Fmisc.git

ovl: Check for casefold consistency when creating new dentries

In a overlayfs with casefold enabled, all new dentries should have
casefold enabled as well. Check this at ovl_create_real().

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index dbd63a74df4b..538a1b2dbb38 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -187,6 +187,13 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
 			/* mkdir is special... */
 			newdentry =  ovl_do_mkdir(ofs, dir, newdentry, attr->mode);
 			err = PTR_ERR_OR_ZERO(newdentry);
+			/* expect to inherit casefolding from workdir/upperdir */
+			if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) {
+				pr_warn_ratelimited("wrong inherited casefold (%pd2)\n",
+						    newdentry);
+				dput(newdentry);
+				err = -EINVAL;
+			}
 			break;
 
 		case S_IFCHR: