Re: [PATCH] ubi: fastmap: Don't produce the initial anchor PEB when fastmap is disabled

[Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>]

Hi,

On Mon, Jun 01, 2020 at 05:11:34PM +0800, Zhihao Cheng wrote:
> Following process triggers a memleak caused by forgetting to release the
> initial anchor PEB (CONFIG_MTD_UBI_FASTMAP is disabled):
> 1. attach -> __erase_worker -> produce the initial anchor PEB
> 2. detach -> ubi_fastmap_close (Do nothing, it should have released the
>    initial anchor PEB)
> 
> Don't produce the initial anchor PEB in __erase_worker() when fastmap
> is disabled.
> 
> Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
> Fixes: f9c34bb529975fe ("ubi: Fix producing anchor PEBs")
> Reported-by: syzbot+d9aab50b1154e3d163f5@xxxxxxxxxxxxxxxxxxxxxxxxx
> ---
>  drivers/mtd/ubi/wl.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> index 5146cce5fe32..5ebe1084a8e7 100644
> --- a/drivers/mtd/ubi/wl.c
> +++ b/drivers/mtd/ubi/wl.c
> @@ -1079,13 +1079,19 @@ static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk)
>  	if (!err) {
>  		spin_lock(&ubi->wl_lock);
>  
> -		if (!ubi->fm_anchor && e->pnum < UBI_FM_MAX_START) {
> +#ifdef CONFIG_MTD_UBI_FASTMAP
> +		if (!ubi->fm_disabled && !ubi->fm_anchor &&
> +		    e->pnum < UBI_FM_MAX_START) {

Rather than introducing another #ifdef you could do a

		if (IS_ENABLED(CONFIG_MTD_UBI_FASTMAP) &&
		    !ubi->fm_disabled && !ubi->fm_anchor &&
		    e->pnum < UBI_FM_MAX_START)

And I am not sure if the IS_ENABLED(CONFIG_MTD_UBI_FASTMAP) is necessary
at all because we do a ubi->fm_disabled = 1 when fastmap is disabled.

Regards,
 Sascha

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