From: Hadi Chokr <hadichokr@icloud.com>
Date: Tue, 28 Apr 2026 10:18:43 +0000 (+0200)
Subject: useradd: fix btrfs subvolume creation for single-component basedir
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;p=thirdparty%2Fshadow.git

useradd: fix btrfs subvolume creation for single-component basedir

dirname() replaces broken stpcpy index arithmetic that produced an
empty string for single-component paths (e.g. /koolhome), causing
statfs to fail and fall back to a regular directory. Use path in
the error message since dirname() modifies btrfs_check in-place,
making it unusable for logging after the call.

Fixes: c1d36a8acb1d (2019-05-04; "Add support for btrfs subvolumes for user homes")
Signed-off-by: Hadi Chokr <hadichokr@icloud.com>
Reviewed-by: Alejandro Colomar <alx@kernel.org>
---

diff --git a/src/useradd.c b/src/useradd.c
index 9210379c8..c0e28ef8b 100644
--- a/src/useradd.c
+++ b/src/useradd.c
@@ -2274,10 +2274,9 @@ static void create_home(const struct option_flags *flags)
 					Prog, path);
 				fail_exit(E_HOMEDIR, process_selinux);
 			}
-			stpcpy(&btrfs_check[strlen(path) - strlen(cp) - 1], "");
-			if (statfs(btrfs_check, &sfs) == -1) {
-				fprintf(stderr, "%s: statfs(\"%s\"): %s\n",
-					Prog, btrfs_check, strerrno());
+			if (statfs(dirname(btrfs_check), &sfs) == -1) {
+				fprintf(stderr, "%s: statfs(dirname(\"%s\")): %s\n",
+					Prog, path, strerrno());
 				fail_exit(E_HOMEDIR, process_selinux);
 			}
 			free(btrfs_check);