[PATCH] ubi: Revert "ubi: wl: Close down wear-leveling before nand is suspended"

[Marten Lindahl]

Hi Zhihao Cheng!

Yes, we discussed this issue in [2], and I thought 5580cdae05ae ("ubi: 
wl: Close down wear-leveling before nand is suspended") was dropped, but 
I see now it got merged.

I agree it should be reverted.

Acked-by: Mårten Lindahl <marten.lindahl at axis.com>

Kind regards

Mårten

On 12/14/24 12:01, Zhihao Cheng wrote:
> Commit 5580cdae05ae ("ubi: wl: Close down wear-leveling before nand is
> suspended") added a reboot notification in UBI layer to shutdown the
> wear-leveling subsystem, which imported an UAF problem[1]. Besides that,
> the method also brings other potential UAF problems, for example:
>         reboot             kworker
>   ubi_wl_reboot_notifier
>    ubi_wl_close
>     ubi_fastmap_close
>      kfree(ubi->fm)
>                       update_fastmap_work_fn
> 		      ubi_update_fastmap
> 		       old_fm = ubi->fm
> 		       if (old_fm && old_fm->e[i]) // UAF!
>
> Actually, the problem fixed by commit 5580cdae05ae ("ubi: wl: Close down
> wear-leveling before nand is suspended") has been solved by commit
> 8cba323437a4 ("mtd: rawnand: protect access to rawnand devices while in
> suspend"), which was discussed in [2]. So we can revert the commit
> 5580cdae05ae ("ubi: wl: Close down wear-leveling before nand is
> suspended") directly.
>
> [1] https://lore.kernel.org/linux-mtd/20241208175211.9406-2-dennis.lamerice@gmail.com/
> [2] https://lore.kernel.org/all/9bf76f5d-12a4-46ff-90d4-4a7f0f47c381@axis.com/
>
> Fixes: 5580cdae05ae ("ubi: wl: Close down wear-leveling before nand is suspended")
> Reported-by: Dennis Lam <dennis.lamerice at gmail.com>
> Closes: https://lore.kernel.org/linux-mtd/20241208175211.9406-2-dennis.lamerice@gmail.com/
> Signed-off-by: Zhihao Cheng <chengzhihao1 at huawei.com>
> ---
>   drivers/mtd/ubi/ubi.h |  2 --
>   drivers/mtd/ubi/wl.c  | 21 ---------------------
>   2 files changed, 23 deletions(-)
>
> diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
> index 26cc53ad34ec..c792b9bcab9b 100644
> --- a/drivers/mtd/ubi/ubi.h
> +++ b/drivers/mtd/ubi/ubi.h
> @@ -549,7 +549,6 @@ struct ubi_debug_info {
>    * @peb_buf: a buffer of PEB size used for different purposes
>    * @buf_mutex: protects @peb_buf
>    * @ckvol_mutex: serializes static volume checking when opening
> - * @wl_reboot_notifier: close all wear-leveling work before reboot
>    *
>    * @dbg: debugging information for this UBI device
>    */
> @@ -652,7 +651,6 @@ struct ubi_device {
>   	void *peb_buf;
>   	struct mutex buf_mutex;
>   	struct mutex ckvol_mutex;
> -	struct notifier_block wl_reboot_notifier;
>   
>   	struct ubi_debug_info dbg;
>   };
> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> index 4f6f339d8fb8..fbd399cf6503 100644
> --- a/drivers/mtd/ubi/wl.c
> +++ b/drivers/mtd/ubi/wl.c
> @@ -89,7 +89,6 @@
>   #include <linux/crc32.h>
>   #include <linux/freezer.h>
>   #include <linux/kthread.h>
> -#include <linux/reboot.h>
>   #include "ubi.h"
>   #include "wl.h"
>   
> @@ -128,8 +127,6 @@ static int self_check_in_wl_tree(const struct ubi_device *ubi,
>   				 struct ubi_wl_entry *e, struct rb_root *root);
>   static int self_check_in_pq(const struct ubi_device *ubi,
>   			    struct ubi_wl_entry *e);
> -static int ubi_wl_reboot_notifier(struct notifier_block *n,
> -				  unsigned long state, void *cmd);
>   
>   /**
>    * wl_tree_add - add a wear-leveling entry to a WL RB-tree.
> @@ -1953,13 +1950,6 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
>   	if (!ubi->ro_mode && !ubi->fm_disabled)
>   		ubi_ensure_anchor_pebs(ubi);
>   #endif
> -
> -	if (!ubi->wl_reboot_notifier.notifier_call) {
> -		ubi->wl_reboot_notifier.notifier_call = ubi_wl_reboot_notifier;
> -		ubi->wl_reboot_notifier.priority = 1; /* Higher than MTD */
> -		register_reboot_notifier(&ubi->wl_reboot_notifier);
> -	}
> -
>   	return 0;
>   
>   out_free:
> @@ -2005,17 +1995,6 @@ void ubi_wl_close(struct ubi_device *ubi)
>   	kfree(ubi->lookuptbl);
>   }
>   
> -static int ubi_wl_reboot_notifier(struct notifier_block *n,
> -				  unsigned long state, void *cmd)
> -{
> -	struct ubi_device *ubi;
> -
> -	ubi = container_of(n, struct ubi_device, wl_reboot_notifier);
> -	ubi_wl_close(ubi);
> -
> -	return NOTIFY_DONE;
> -}
> -
>   /**
>    * self_check_ec - make sure that the erase counter of a PEB is correct.
>    * @ubi: UBI device description object