Re: [[PATCH] MTD: fix slab-use-after-free due to dangling pointer in notifier chain] MTD: fix slab-use-after-free due to dangling pointer in notifier chain

[Dennis Lam]

On Sun, Dec 8, 2024 at 3:51 AM Dennis Lam <dennis.lamerice@xxxxxxxxx> wrote:
>
> When attaching MTDs, a reboot notifier is added to the blocking
> notification chain. However, when detaching a MTD and freeing its
> related objects, the notifier is never unregistered from the
> notification chain. Thus, when the chain is iterated there is a
> possibility of finding the address of the reboot notifier which has
> already been freed, resulting in a slab-use-after-free error.
>
> To fix this, I added an unregister notifier function in the ubi_wl_close
> function to ensure that the notifier is removed from the chain after the
> device has been detached.
>
> Reported-by: syzbot+0988a383ae7c57b99dd9@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://lore.kernel.org/all/67409091.050a0220.363a1b.013d.GAE@xxxxxxxxxx/T/
> Signed-off-by: Dennis Lam <dennis.lamerice@xxxxxxxxx>
> ---
>  drivers/mtd/ubi/wl.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> index 4f6f339d8fb8..31a1e5515d98 100644
> --- a/drivers/mtd/ubi/wl.c
> +++ b/drivers/mtd/ubi/wl.c
> @@ -1995,6 +1995,7 @@ static void protection_queue_destroy(struct ubi_device *ubi)
>  void ubi_wl_close(struct ubi_device *ubi)
>  {
>         dbg_wl("close the WL sub-system");
> +       unregister_reboot_notifier(&ubi->wl_reboot_notifier);
>         ubi_fastmap_close(ubi);
>         shutdown_work(ubi);
>         protection_queue_destroy(ubi);
> --
> 2.47.0
>

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