Re: slab-out-of-bounds in iov_iter_revert()

From: Qian Cai
Date: Wed Sep 16 2020 - 17:10:01 EST

On Sat, 2020-09-12 at 00:55 +0100, Al Viro wrote:
> On Fri, Sep 11, 2020 at 05:59:04PM -0400, Qian Cai wrote:
> > Super easy to reproduce on today's mainline by just fuzzing for a few
> > minutes
> > on virtiofs (if it ever matters). Any thoughts?
> Usually happens when ->direct_IO() fucks up and reports the wrong amount
> of data written/read. We had several bugs like that in the past - see
> e.g. 85128b2be673 (fix nfs O_DIRECT advancing iov_iter too much).
> Had there been any recent O_DIRECT-related patches on the filesystems
> involved?

This is only reproducible using FUSE/virtiofs so far, so I will stare at
fuse_direct_IO() until someone can beat me to it.