6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Karl Mehltretter <redacted>
[ Upstream commit 6645856f0df3aeecd45519cb611415b4b89c2223 ]
tty_cdev_add() drops the cdev reference when cdev_add() fails, but
leaves driver->cdevs[index] pointing to freed memory.
tty_unregister_device() later passes that stale pointer to cdev_del(),
causing a use-after-free.
Clear the slot after dropping the reference.
Fixes: c1a752ba2d6b ("tty: don't leak cdev in tty_cdev_add()")
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <redacted>
Link: https://patch.msgid.link/20260731181844.11330-5-kmehltretter@gmail.com (local)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/tty_io.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index aaf77a5616ff1..9eceb168137f7 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3156,8 +3156,10 @@ static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
driver->cdevs[index]->ops = &tty_fops;
driver->cdevs[index]->owner = driver->owner;
err = cdev_add(driver->cdevs[index], dev, count);
- if (err)
+ if (err) {
kobject_put(&driver->cdevs[index]->kobj);
+ driver->cdevs[index] = NULL;
+ }
return err;
}
--
2.53.0