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: 7bccd12d27b7e3 ("ubi: Add debugfs file for tracking PEB state")
Fixes: 801c135ce73d5d ("UBI: Unsorted Block Images")
Signed-off-by: Zhihao Cheng <[email protected]>
---
drivers/mtd/ubi/wl.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index ee0100740869..5218e6edde58 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -890,8 +890,11 @@ 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;
}
@@ -1130,14 +1133,18 @@ 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
--
2.31.1