[06/27] UBI: fix use-after-free on error path

Greg KH
2012-01-24T00:12:00Z

From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

commit e57e0d8e818512047fe379157c3f77f1b9fabffb upstream.

When we fail to erase a PEB, we free the corresponding erase entry object,
but then re-schedule this object if the error code was something like -EAGAIN.
Obviously, it is a bug to use the object after we have freed it.

Reported-by: Emese Revfy <re.emese@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/mtd/ubi/wl.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -1036,7 +1036,6 @@ static int erase_worker(struct ubi_devic

ubi_err("failed to erase PEB %d, error %d", pnum, err);
kfree(wl_wrk);
- kmem_cache_free(ubi_wl_entry_slab, e);

if (err == -EINTR || err == -ENOMEM || err == -EAGAIN ||
err == -EBUSY) {
@@ -1049,14 +1048,16 @@ static int erase_worker(struct ubi_devic
goto out_ro;
}
return err;
- } else if (err != -EIO) {
+ }
+
+ kmem_cache_free(ubi_wl_entry_slab, e);
+ if (err != -EIO)
/*
* If this is not %-EIO, we have no idea what to do. Scheduling
* this physical eraseblock for erasure again would cause
* errors again and again. Well, lets switch to R/O mode.
*/
goto out_ro;
- }

/* It is %-EIO, the PEB went bad */