| From: |
| Eric Sandeen <sandeen-AT-sandeen.net> |
| To: |
| Eric Biggers <ebiggers3-AT-gmail.com>, "Darrick J. Wong" <darrick.wong-AT-oracle.com> |
| Subject: |
| Re: INFO: task hung in xlog_grant_head_check |
| Date: |
| Wed, 23 May 2018 13:01:59 -0500 |
| Message-ID: |
| <a52266f9-0096-b28c-c01c-046ababcfe3a@sandeen.net> |
| Cc: |
| Dave Chinner <david-AT-fromorbit.com>, Brian Foster <bfoster-AT-redhat.com>, syzbot <syzbot+568245b88fbaedcb1959-AT-syzkaller.appspotmail.com>, linux-kernel-AT-vger.kernel.org, linux-xfs-AT-vger.kernel.org, syzkaller-bugs-AT-googlegroups.com |
| Archive-link: |
| Article |
On 5/23/18 11:20 AM, Eric Biggers wrote:
> Hi Darrick,
...
> Now, if you *really* don't want syzbot to report XFS bugs as you believe XFS
> contains known unfixable bugs or for other reasons, you can formally ask Dmitry
> to remove CONFIG_XFS_FS from the syzbot config. But of course that doesn't make
> the bugs go away, it just makes the bug reports go away; you'll have to fix them
> eventually anyway, one way or another.
I'd revise that to "have to fix /some/ of them anyway."
What I'm personally hung up on are the bugs where the "exploit" involves merely
mounting a crafted filesystem that in reality would never (until the heat death
of the universe) corrupt itself into that state on its own; it's the "malicious
image" case, which is quite different than exposing fundamental bugs like the
SB_BORN race or or the user-exploitable ext4 flaw you mentioned in your reply.
Those are more insidious and/or things which can be hit by real users in real life.
I don't know if I can win the "malicious images aren't a critical security
threat" battle, but I do think they are at least a different class of flaws,
because as Dave said, mount is supposed to be a privileged operation.
In a perfect world we'd fix them anyway, but I don't know that our resource
pool can keep up with your google-scale bot and still make progress in other
critical areas.
Anyway, the upshot is that we're probably just not going to care much about V4
filesystem oops-or-hang-on-mount bugs. Those problems are solved (largely) with
V5 filesystem format. Maybe I /will/ propose a system-wide tunable to disallow
V4 for those who are worried about such things.
To Darrick's points about more collaboration, I still wish that our requests
for more traditional fs fuzzer reporting (i.e. a filesystem image) weren't met
with such resistance.Tailoring your bug reports to the needs of the developer
community you're interacting with seems like a pretty reasonable thing to do.
As an aside, I wonder how much coverage of the V5 format code syzkaller /has/
achieved; that would be another useful datapoint google could provide - if
syzkaller is in fact traversing the V5 codepaths and isn't turning anything
up, that'd be pretty useful to know.
Thanks,
-Eric
