[PATCH 2/2] fs: jffs2: refuse to mount non-MTD devices

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

From: Ahmad Fatoum <a.fatoum@barebox.org>

jffs2 only works on MTD, but nothing keeps it from being probed for
other devices. mount -t jffs2 on a block device leaves the MTD pointer
NULL and jffs2_do_fill_super() dereferences it right away.

Let's fail the probe instead, like ubifs does when it's not given a UBI
volume.

Fixes: 831b3312e5fe ("fs: jffs2: add initial support for reading jffs2")
Assisted-by: Claude:opus-5.5
Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 fs/jffs2/fs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index 84f39a0f2a24..8cbe15850e37 100644
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -407,6 +407,11 @@ static int jffs2_probe(struct device *dev)
 	if (ret)
 		goto err_out;
 
+	if (!fsdev->cdev->mtd) {
+		dev_err(dev, "%s is not an MTD device\n", fsdev->backingstore);
+		return -EINVAL;
+	}
+
 	ctx = kzalloc(sizeof(struct jffs2_sb_info), GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;
-- 
2.47.3