Silverhadch master

lib/Makefile.am

@@ -290,7 +290,7 @@ libshadow_la_SOURCES += tcbfuncs.c tcbfuncs.h
 endif
 
 if WITH_BTRFS
-libshadow_la_SOURCES += btrfs.c
+libshadow_la_SOURCES += btrfs.c btrfs.h
 endif
 
 if ENABLE_LASTLOG

lib/btrfs.c

@@ -1,3 +1,7 @@
+#include "config.h"
+
+#include "btrfs.h"
+
 #include <linux/btrfs_tree.h>
 #include <linux/magic.h>
 #include <sys/statfs.h>
@@ -60,15 +64,15 @@ int btrfs_remove_subvolume(const char *path)
  */
 int btrfs_is_subvolume(const char *path)
 {
-	struct stat st;
-	int ret;
+	struct stat    st;
+	struct statfs  sfs;
 
-	ret = is_btrfs(path);
-	if (ret <= 0)
-		return ret;
+	if (statfs(path, &sfs) == -1)
+		return -1;
+	if (!is_btrfs(&sfs))
+		return 0;
 
-	ret = stat(path, &st);
-	if (ret == -1)
+	if (stat(path, &st) == -1)
 		return -1;
 
 	if (st.st_ino != BTRFS_FIRST_FREE_OBJECTID || !S_ISDIR(st.st_mode)) {
@@ -80,15 +84,8 @@ int btrfs_is_subvolume(const char *path)
 
 
 /* Adapted from btrfsprogs */
-int is_btrfs(const char *path)
+bool
+is_btrfs(const struct statfs *sfs)
 {
-	struct statfs sfs;
-	int ret;
-
-	ret = statfs(path, &sfs);
-	if (ret == -1)
-		return -1;
-
-	return sfs.f_type == BTRFS_SUPER_MAGIC;
+	return sfs->f_type == BTRFS_SUPER_MAGIC;
 }
-

lib/btrfs.h

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2026, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_BTRFS_H_
+#define SHADOW_INCLUDE_LIB_BTRFS_H_
+
+
+#include "config.h"
+
+#include <stdbool.h>
+#include <sys/statfs.h>
+
+
+#ifdef WITH_BTRFS
+int btrfs_create_subvolume(const char *path);
+int btrfs_remove_subvolume(const char *path);
+int btrfs_is_subvolume(const char *path);
+bool is_btrfs(const struct statfs *sfs);
+#endif
+
+
+#endif  // include guard

lib/prototypes.h

@@ -49,14 +49,6 @@ extern int expire (const struct passwd *, /*@null@*/const struct spwd *);
 /* isexpired.c */
 extern int isexpired (const struct passwd *, /*@null@*/const struct spwd *);
 
-/* btrfs.c */
-#ifdef WITH_BTRFS
-extern int btrfs_create_subvolume(const char *path);
-extern int btrfs_remove_subvolume(const char *path);
-extern int btrfs_is_subvolume(const char *path);
-extern int is_btrfs(const char *path);
-#endif
-
 /* basename() renamed to Basename() to avoid libc name space confusion */
 /* basename.c */
 extern /*@observer@*/const char *Basename (const char *str);

man/useradd.8.xml

@@ -2,6 +2,7 @@
 <!--
    SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
    SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
+   SPDX-FileCopyrightText: 2025 - 2026, Hadi Chokr
    SPDX-License-Identifier: BSD-3-Clause
 -->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
@@ -156,8 +157,30 @@
 		regardless of any configuration file settings.
 	  </para>
 	  <para>
-	    Note: this feature works only if the underlying filesystem supports
-	    Btrfs subvolumes.
+	    If the parent directory of the user's home directory is
+	    <emphasis>not</emphasis> on a Btrfs filesystem,
+	    <command>useradd</command> will <emphasis>not</emphasis> create a
+	    subvolume.
+	    Instead, it creates a regular directory,
+	    prints a warning to standard error,
+	    and logs the event via syslog at level
+	    <constant>LOG_WARN</constant>.
+	    The user account is still created successfully.
+	  </para>
+	  <para>
+	    If the filesystem type cannot be determined (e.g., because of
+	    insufficient permissions, an I/O error,
+	    or a
+	    <citerefentry>
+	      <refentrytitle>statfs</refentrytitle>
+	      <manvolnum>2</manvolnum>
+	    </citerefentry>
+	    failure),
+	    <command>useradd</command> treats this as a fatal error:
+	    the home directory is not created,
+	    the command exits with a non‑zero status
+	    (<literal>E_HOMEDIR</literal>, 12),
+	    and an error message is printed.
 	  </para>
 	</listitem>
       </varlistentry>
@@ -184,7 +207,7 @@
 	    user's login directory. The default is to append the
 	    <replaceable>LOGIN</replaceable> name to
 	    <replaceable>BASE_DIR</replaceable> and use that as the
-	    login directory name.  
+	    login directory name.
 	    The directory <replaceable>HOME_DIR</replaceable> is not created by
 	    default.  However it will be created for non-system users if either the
 	    <option>-m</option> flag is specified or
@@ -399,7 +422,7 @@
 	</term>
 	<listitem>
 	  <para>
-	    Create the user's home directory if it does not exist. 
+	    Create the user's home directory if it does not exist.
 	    The files and directories contained in the skeleton directory
 	    (which can be defined with the <option>-k</option> option)
 	    will be copied to the home directory.
@@ -489,7 +512,7 @@
             password himself.
 	  </para>
 	  <para>
-	    <emphasis role="bold">Note:</emphasis>Avoid this option on the command  
+	    <emphasis role="bold">Note:</emphasis>Avoid this option on the command
 	     line because the password (or encrypted password) will
 	    be visible by users listing the processes.
 	  </para>

src/useradd.c

@@ -1,11 +1,11 @@
-/*
- * SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
- * SPDX-FileCopyrightText: 1996 - 2000, Marek Michałkiewicz
- * SPDX-FileCopyrightText: 2000 - 2006, Tomasz Kłoczko
- * SPDX-FileCopyrightText: 2007 - 2012, Nicolas François
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
+// SPDX-FileCopyrightText: 1991-1994, Julianne Frances Haugh
+// SPDX-FileCopyrightText: 1996-2000, Marek Michałkiewicz
+// SPDX-FileCopyrightText: 2000-2006, Tomasz Kłoczko
+// SPDX-FileCopyrightText: 2007-2012, Nicolas François
+// SPDX-FileCopyrightText: 2025-2026, Hadi Chokr
+// SPDX-FileCopyrightText: 2026, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
 
 #include "config.h"
 
@@ -25,6 +25,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <time.h>
@@ -2249,6 +2250,8 @@ static void create_home(const struct option_flags *flags)
 	   owner root:root.
 	 */
 	for (cp = strtok(bhome, "/"); cp != NULL; cp = strtok(NULL, "/")) {
+		bool  dir_created;
+
 		/* Avoid turning a relative path into an absolute path. */
 		if (strprefix(bhome, "/") || !streq(path, ""))
 			strcat(path, "/");
@@ -2258,13 +2261,11 @@ static void create_home(const struct option_flags *flags)
 			continue;
 		}
 
-		/* Check if parent directory is BTRFS, fail if requesting
-		   subvolume but no BTRFS. The paths could be different by the
-		   trailing slash
-		 */
+		dir_created = false;
 #if WITH_BTRFS
 		if (subvolflg && (strlen(prefix_user_home) - (int)strlen(path)) <= 1) {
 			char *btrfs_check = strdup(path);
+			struct statfs  sfs;
 
 			if (!btrfs_check) {
 				fprintf(stderr,
@@ -2273,27 +2274,33 @@ static void create_home(const struct option_flags *flags)
 				fail_exit(E_HOMEDIR, process_selinux);
 			}
 			stpcpy(&btrfs_check[strlen(path) - strlen(cp) - 1], "");
-			if (is_btrfs(btrfs_check) <= 0) {
-				fprintf(stderr,
-					_("%s: home directory \"%s\" must be mounted on BTRFS\n"),
-					Prog, path);
+			if (statfs(btrfs_check, &sfs) == -1) {
+				fprintf(stderr, "%s: statfs(\"%s\"): %s\n",
+					Prog, btrfs_check, strerrno());
 				fail_exit(E_HOMEDIR, process_selinux);
 			}
 			free(btrfs_check);
-			// make subvolume to mount for user instead of directory
-			if (btrfs_create_subvolume(path)) {
+			if (!is_btrfs(&sfs)) {
 				fprintf(stderr,
-					_("%s: failed to create BTRFS subvolume: %s\n"),
-					Prog, path);
-				fail_exit(E_HOMEDIR, process_selinux);
+				        _("%s: warning: \"%s\" is not on BTRFS; creating regular directory instead of subvolume\n"),
+				        Prog, prefix_user_home);
+			} else {
+				if (btrfs_create_subvolume(path)) {
+					fprintf(stderr,
+					        _("%s: failed to create BTRFS subvolume: %s\n"),
+						Prog, path);
+					fail_exit(E_HOMEDIR, process_selinux);
+				}
+				dir_created = true;
 			}
 		}
-		else
 #endif
-		if (mkdir(path, 0) != 0) {
-			fprintf(stderr, _("%s: cannot create directory %s\n"),
-				Prog, path);
-			fail_exit(E_HOMEDIR, process_selinux);
+		if (!dir_created) {
+			if (mkdir(path, 0) != 0) {
+				fprintf(stderr, _("%s: cannot create directory %s\n"),
+					Prog, path);
+				fail_exit(E_HOMEDIR, process_selinux);
+			}
 		}
 		if (chown(path, 0, 0) < 0) {
 			fprintf(stderr,

src/usermod.c

@@ -32,6 +32,7 @@
 #include "alloc/malloc.h"
 #include "atoi/a2i.h"
 #include "atoi/getnum.h"
+#include "btrfs.h"
 #include "chkname.h"
 #include "defines.h"
 #include "faillog.h"