[PATCH v2025.09.y 24/49] fs: qemu_fw_cfg: handle non-existent opt/org.barebox.env key gracefully

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

QEMU fw_cfg file system driver is the sole user of
defaultenv_append_runtime_directory() and it passes a path that's not
necessarily available.

When that happens, this is not noticed until the loop in defaultenv_load()
aborts early with an -ENOENT preventing load of an external environment.

Fix this as by not adding the directory if it doesn't exist.

Fixes: 31dfb561d1a4 ("fs: qemu_fw_cfg: support populating environment via QEMU fw_cfg")
Reported-by: Jan Lübbe <j.luebbe@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20251125062603.2614867-5-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
(cherry picked from commit cfa4f62c104c6b9232b5bad5b0a5e7e5341a9870)
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 fs/qemu_fw_cfg.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/qemu_fw_cfg.c b/fs/qemu_fw_cfg.c
index 49115beeb21d..b28f4df99c25 100644
--- a/fs/qemu_fw_cfg.c
+++ b/fs/qemu_fw_cfg.c
@@ -20,6 +20,8 @@
 #include <linux/err.h>
 #include <linux/ctype.h>
 
+#define FW_CFG_BAREBOX_ENV	"/mnt/fw_cfg/by_name/opt/org.barebox.env"
+
 struct fw_cfg_fs_inode {
 	struct inode inode;
 	const char *name;
@@ -375,8 +377,6 @@ static int fw_cfg_fs_probe(struct device *dev)
 	if (ret)
 		goto free_data;
 
-	defaultenv_append_runtime_directory("/mnt/fw_cfg/by_name/opt/org.barebox.env");
-
 	return 0;
 free_data:
 	free(data);
@@ -411,10 +411,12 @@ coredevice_initcall(qemu_fw_cfg_fs_init);
 
 static int qemu_fw_cfg_early_mount(void)
 {
+	struct stat s;
 	int fd;
 
 	/*
-	 * Also triggers the automount, so ramfb device can be detected
+	 * Also triggers the automount, so both ramfb device can be detected
+	 * and environment can be loaded
 	 */
 	fd = open("/mnt/fw_cfg/by_name/etc/ramfb", O_WRONLY);
 	if (fd >= 0) {
@@ -424,6 +426,9 @@ static int qemu_fw_cfg_early_mount(void)
 		platform_device_register(dev);
 	}
 
+	if (!stat(FW_CFG_BAREBOX_ENV, &s) && S_ISDIR(s.st_mode))
+		defaultenv_append_runtime_directory(FW_CFG_BAREBOX_ENV);
+
 	return 0;
 }
 late_initcall(qemu_fw_cfg_early_mount);
-- 
2.47.3