[PATCH] ubi: fastmap: fix slab corruption

[Rabin Vincent]

On Mon, Mar 20, 2017 at 04:17:06PM +0100, Rabin Vincent wrote:
>  /**
>   * ubi_scan_fastmap - scan the fastmap.
>   * @ubi: UBI device object
> @@ -847,7 +865,7 @@ int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
>  	struct ubi_vid_hdr *vh;
>  	struct ubi_ec_hdr *ech;
>  	struct ubi_fastmap_layout *fm;
> -	struct ubi_ainf_peb *tmp_aeb, *aeb;
> +	struct ubi_ainf_peb *aeb;
>  	int i, used_blocks, pnum, fm_anchor, ret = 0;
>  	size_t fm_size;
>  	__be32 crc, tmp_crc;
> @@ -857,9 +875,18 @@ int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
>  	if (fm_anchor < 0)
>  		return UBI_NO_FASTMAP;
>  
> -	/* Move all (possible) fastmap blocks into our new attach structure. */
> -	list_for_each_entry_safe(aeb, tmp_aeb, &scan_ai->fastmap, u.list)
> -		list_move_tail(&aeb->u.list, &ai->fastmap);
> +	/* Copy all (possible) fastmap blocks into our new attach structure. */
> +	list_for_each_entry(aeb, &scan_ai->fastmap, u.list) {
> +		struct ubi_ainf_peb *new;
> +
> +		new = clone_aeb(ai, aeb);
> +		if (!new) {
> +			ret = -ENOMEM;
> +			goto out;

I just noticed that this should be just a return instead of a goto out
since we haven't locked the semaphore yet.  I'll send a v2 with that
fixed if you think that the rest of the patch look sane.