linux-kernel - Re: slab-out-of-bounds in iov_iter

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Message-ID: <87ded87d232d9cf87c9c64495bf9190be0e0b6e8.camel@redhat.com>
Date:   Wed, 16 Sep 2020 17:09:49 -0400
From:   Qian Cai <cai@...hat.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     torvalds@...ux-foundation.org, vgoyal@...hat.com,
        miklos@...redi.hu, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: slab-out-of-bounds in iov_iter_revert()

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.