On Sun, 2018-04-22 at 15:53 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Richard Weinberger <[email protected]> > > commit 29b7a6fa1ec07e8480b0d9caf635a4498a438bf4 upstream. > > At this point UBI volumes have already been free()'ed and fastmap can no > longer access these data structures.
I don't see how this change can fix a use-after-free. If this function can be called with *ubi already freed, then the rest of the function body is also not safe to run. But I don't think that is the case. ubi->fm_work doesn't depend on any other structure (except a global workqueue, which won't go away). It seems to me that the bug is really a race condition, and removing the flush_work() makes it harder to hit that condition. The proper fix would be to call flush_work() (or cancel_work_sync()) before the UBI volumes are freed. Ben. > Reported-by: Martin Townsend <[email protected]> > Fixes: 74cdaf24004a ("UBI: Fastmap: Fix memory leaks while closing the WL > sub-system") > Cc: [email protected] > Signed-off-by: Richard Weinberger <[email protected]> > Signed-off-by: Greg Kroah-Hartman <[email protected]> > > --- > drivers/mtd/ubi/fastmap-wl.c | 1 - > 1 file changed, 1 deletion(-) > > --- a/drivers/mtd/ubi/fastmap-wl.c > +++ b/drivers/mtd/ubi/fastmap-wl.c > @@ -360,7 +360,6 @@ static void ubi_fastmap_close(struct ubi > { > int i; > > - flush_work(&ubi->fm_work); > return_unused_pool_pebs(ubi, &ubi->fm_pool); > return_unused_pool_pebs(ubi, &ubi->fm_wl_pool); > > > > -- Ben Hutchings Software Developer, Codethink Ltd.
