On Sat 07-10-17 03:02:17, Al Viro wrote: > On Fri, Oct 06, 2017 at 06:37:11PM -0700, Linus Torvalds wrote: > > On Fri, Oct 6, 2017 at 6:20 PM, Jia-Ju Bai <baijiaju1990@xxxxxxx> wrote: > > > > > > To fix it, GFP_KERNEL is replaced with GFP_ATOMIC. > > > This bug is found by my static analysis tool and my code review. > > > > I'm not saying your patch is wrong, but it's a shame that we do that > > extra allocation in match_number() and match_u64int(), and that we > > don't have anything that is just size-limited. > > > > And there really isn't anything saying that we shouldn't do the same > > silly thing to match_u64int(). Maybe we don't have any actual users > > that need it for now, but still.. > > > > Oh well. > > > > I do wonder if we shouldn't just use something like > > > > "skip leading zeroes, copy to size-limited stack location instead" > > > > because the input length really *is* limited once you skip leading > > zeroes (and whatever base marker we have). We might have at most a > > 64-bit value in octal, so 22 bytes max. > > > > But I guess just changing the two GFP_KERNEL's to GFP_ATOMIC is much simpler. > > There's match_strdup() as well... > > FWIW, ext2 side also looks fishy; it might be cleaner if we > collected new state into some object and applied it only after the last > possible failure exit. The entire "restore the original state" logics > would go away... Well, it's not like the restore logic would be that difficult for ext2. But I agree that running the whole parsing logic under a spinlock is unnecessary and accumulating all the changes in one structure and then applying them looks like a cleaner way to go. I'll look into that. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
