Commit 1cb14c06 authored Jul 30, 2022 by Zhihao Cheng Committed by Greg Kroah-Hartman Mar 11, 2023

ubi: Fix UAF wear-leveling entry in eraseblk_count_seq_show()

[ Upstream commit a240bc5c43130c6aa50831d7caaa02a1d84e1bce ]

Wear-leveling entry could be freed in error path, which may be accessed
again in eraseblk_count_seq_show(), for example:

__erase_worker                eraseblk_count_seq_show
                                wl = ubi->lookuptbl[*block_number]
				if (wl)
  wl_entry_destroy
    ubi->lookuptbl[e->pnum] = NULL
    kmem_cache_free(ubi_wl_entry_slab, e)
		                   erase_count = wl->ec  // UAF!

Wear-leveling entry updating/accessing in ubi->lookuptbl should be
protected by ubi->wl_lock, fix it by adding ubi->wl_lock to serialize
wl entry accessing between wl_entry_destroy() and
eraseblk_count_seq_show().

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216305


Fixes: 7bccd12d ("ubi: Add debugfs file for tracking PEB state")
Fixes: 801c135c ("UBI: Unsorted Block Images")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 7fcbc41d

drivers/mtd/ubi/wl.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -879,8 +879,11 @@ static int wear_leveling_worker(struct ubi_device ubi, struct ubi_work wrk,

		err = do_sync_erase(ubi, e1, vol_id, lnum, 0);
		if (err) {
		if (e2)
		if (e2) {
		spin_lock(&ubi->wl_lock);
		wl_entry_destroy(ubi, e2);
		spin_unlock(&ubi->wl_lock);
		}
		goto out_ro;
		}

		@@ -1110,14 +1113,18 @@ static int __erase_worker(struct ubi_device ubi, struct ubi_work wl_wrk)
		/* Re-schedule the LEB for erasure */
		err1 = schedule_erase(ubi, e, vol_id, lnum, 0, false);
		if (err1) {
		spin_lock(&ubi->wl_lock);
		wl_entry_destroy(ubi, e);
		spin_unlock(&ubi->wl_lock);
		err = err1;
		goto out_ro;
		}
		return err;
		}

		spin_lock(&ubi->wl_lock);
		wl_entry_destroy(ubi, e);
		spin_unlock(&ubi->wl_lock);
		if (err != -EIO)
		/*
		* If this is not %-EIO, we have no idea what to do. Scheduling