From: Andrea Arcangeli <aarcange@redhat.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Konstantin Khlebnikov <koct9i@gmail.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: fs: use-after-free in userfaultfd_exit
Date: Thu, 2 Mar 2017 00:13:34 +0100 [thread overview]
Message-ID: <20170301231334.GO5816@redhat.com> (raw)
In-Reply-To: <CACT4Y+Z188Wehaes7iTo5m3PLiPgusj86f39kuN-O2HeDvQEWg@mail.gmail.com>
On Wed, Mar 01, 2017 at 07:48:00PM +0100, Dmitry Vyukov wrote:
> Hello,
>
> I've got the following use-after-free report while running syzkaller
> fuzzer on 86292b33d4b79ee03e2f43ea0381ef85f077c760:
Yes, I posted the fix for this one last Friday, I found it during
stress testing, it triggered the first time post-upstream merging
despite I was running the same stress testing with SLUB poisoning
enabled before.
This affects all apps, also the ones that don't use userfaultfd, it's
a locking issue. Furthermore the cost of userfaultfd_exit was not
acceptable, if something it had to be activated by a flag in mm->flags
(such an optimization would have been absolutely trivial though).
Thankfully I realized another feature (UFFDIO_COPY -ENOSPC retval) can
provide the same information at zero cost so I could drop
userfaultfd_exit as a whole.
https://marc.info/?l=linux-mm&m=148796041217814&w=2
The fix is already included in -mm along with the other fix for
VM_FAULT_NOPAGE.
Thanks,
Andrea
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prev parent reply other threads:[~2017-03-01 23:13 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-01 18:48 fs: use-after-free in userfaultfd_exit Dmitry Vyukov
2017-03-01 23:13 ` Andrea Arcangeli [this message]
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