This is a note to let you know that I've just added the patch titled rpmsg: char: Fix race between the release of rpmsg_eptdev and cdev to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: rpmsg-char-fix-race-between-the-release-of-rpmsg_ept.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit e1be1fecda528542d0570654b43cf543ac682b36 Author: Matthias Kaehlcke <mka@xxxxxxxxxxxx> Date: Mon Jan 10 10:47:37 2022 -0800 rpmsg: char: Fix race between the release of rpmsg_eptdev and cdev [ Upstream commit 7a534ae89e34e9b51acb5a63dd0f88308178b46a ] struct rpmsg_eptdev contains a struct cdev. The current code frees the rpmsg_eptdev struct in rpmsg_eptdev_destroy(), but the cdev is a managed object, therefore its release is not predictable and the rpmsg_eptdev could be freed before the cdev is entirely released. The cdev_device_add/del() API was created to address this issue (see commit '233ed09d7fda ("chardev: add helper function to register char devs with a struct device")'), use it instead of cdev add/del(). Fixes: c0cdc19f84a4 ("rpmsg: Driver for user space endpoint interface") Suggested-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220110104706.v6.2.Idde68b05b88d4a2e6e54766c653f3a6d9e419ce6@changeid Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c index ba85f5d11960a..49dd5a2009982 100644 --- a/drivers/rpmsg/rpmsg_char.c +++ b/drivers/rpmsg/rpmsg_char.c @@ -92,7 +92,7 @@ static int rpmsg_eptdev_destroy(struct device *dev, void *data) /* wake up any blocked readers */ wake_up_interruptible(&eptdev->readq); - device_del(&eptdev->dev); + cdev_device_del(&eptdev->cdev, &eptdev->dev); put_device(&eptdev->dev); return 0; @@ -335,7 +335,6 @@ static void rpmsg_eptdev_release_device(struct device *dev) ida_simple_remove(&rpmsg_ept_ida, dev->id); ida_simple_remove(&rpmsg_minor_ida, MINOR(eptdev->dev.devt)); - cdev_del(&eptdev->cdev); kfree(eptdev); } @@ -380,19 +379,13 @@ static int rpmsg_eptdev_create(struct rpmsg_ctrldev *ctrldev, dev->id = ret; dev_set_name(dev, "rpmsg%d", ret); - ret = cdev_add(&eptdev->cdev, dev->devt, 1); + ret = cdev_device_add(&eptdev->cdev, &eptdev->dev); if (ret) goto free_ept_ida; /* We can now rely on the release function for cleanup */ dev->release = rpmsg_eptdev_release_device; - ret = device_add(dev); - if (ret) { - dev_err(dev, "device_add failed: %d\n", ret); - put_device(dev); - } - return ret; free_ept_ida: