Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0

From	Johannes Weiner <hannes@cmpxchg.org>
Newsgroups	linux.kernel
Subject	Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0
Date	2016-12-23 09:40 +0100
Message-ID	<sRtyp-4vW-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <sQZh0-1Xw-21@gated-at.bofh.it> <sR3Xj-51C-3@gated-at.bofh.it> <sR4qm-5dV-27@gated-at.bofh.it> <sRi9Y-5GP-25@gated-at.bofh.it> <sRsCl-3UM-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Fri, Dec 23, 2016 at 02:32:41AM -0500, Johannes Weiner wrote:
> On Thu, Dec 22, 2016 at 12:22:27PM -0800, Hugh Dickins wrote:
> > On Wed, 21 Dec 2016, Linus Torvalds wrote:
> > > On Wed, Dec 21, 2016 at 9:13 PM, Dave Chinner <david@fromorbit.com> wrote:
> > > > I unmounted the fs, mkfs'd it again, ran the
> > > > workload again and about a minute in this fired:
> > > >
> > > > [628867.607417] ------------[ cut here ]------------
> > > > [628867.608603] WARNING: CPU: 2 PID: 16925 at mm/workingset.c:461 shadow_lru_isolate+0x171/0x220
> > > 
> > > Well, part of the changes during the merge window were the shadow
> > > entry tracking changes that came in through Andrew's tree. Adding
> > > Johannes Weiner to the participants.
> > > 
> > > > Now, this workload does not touch the page cache at all - it's
> > > > entirely an XFS metadata workload, so it should not really be
> > > > affecting the working set code.
> > > 
> > > Well, I suspect that anything that creates memory pressure will end up
> > > triggering the working set code, so ..
> > > 
> > > That said, obviously memory corruption could be involved and result in
> > > random issues too, but I wouldn't really expect that in this code.
> > > 
> > > It would probably be really useful to get more data points - is the
> > > problem reliably in this area, or is it going to be random and all
> > > over the place.
> > 
> > Data point: kswapd got WARNING on mm/workingset.c:457 in shadow_lru_isolate,
> > soon followed by NULL pointer deref in list_lru_isolate, one time when
> > I tried out Sunday's git tree.  Not seen since, I haven't had time to
> > investigate, just set it aside as something to worry about if it happens
> > again.  But it looks like shadow_lru_isolate() has issues beyond Dave's
> > case (I've no XFS and no iscsi), suspect unrelated to his other problems.
> 
> This seems consistent with what Dave observed: we encounter regular
> pages in radix tree nodes on the shadow LRU that should only contain
> nodes full of exceptional shadow entries. It could be an issue in the
> new slot replacement code and the node tracking callback.

Both encounters seem to indicate use-after-free. Dave's node didn't
warn about an unexpected node->count / node->exceptional state, but
had entries that were inconsistent with that. Hugh got the counter
warning but crashed on a list_head that's not NULLed in a live node.

workingset_update_node() should be called on page cache radix tree
leaf nodes that go empty. I must be missing an update_node callback
where a leaf node gets freed somewhere.

Thread

[4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-14 23:30 +0100
  Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-14 23:40 +0100
    Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Chris Leech <cleech@redhat.com> - 2016-12-16 20:00 +0100
      Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-21 23:30 +0100
        Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-22 00:30 +0100
          Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Chris Leech <cleech@redhat.com> - 2016-12-22 01:20 +0100
            Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 06:20 +0100
              Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-22 06:50 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 08:00 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Chris Leech <cleech@redhat.com> - 2016-12-22 20:00 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Ming Lei <tom.leiming@gmail.com> - 2016-12-23 01:00 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Chris Leech <cleech@redhat.com> - 2016-12-23 01:10 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at         iscsi_tcp_segment_done+0x20d/0x2e0 Christoph Hellwig <hch@lst.de> - 2016-12-23 11:10 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-23 20:50 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at         iscsi_tcp_segment_done+0x20d/0x2e0 Christoph Hellwig <hch@lst.de> - 2016-12-24 10:50 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at         iscsi_tcp_segment_done+0x20d/0x2e0 Christoph Hellwig <hch@lst.de> - 2016-12-24 11:10 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at         iscsi_tcp_segment_done+0x20d/0x2e0 Christoph Hellwig <hch@lst.de> - 2016-12-24 14:20 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Hannes Reinecke <hare@suse.de> - 2016-12-24 14:20 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Hugh Dickins <hughd@google.com> - 2016-12-22 21:30 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Johannes Weiner <hannes@cmpxchg.org> - 2016-12-23 08:40 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Johannes Weiner <hannes@cmpxchg.org> - 2016-12-23 09:40 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Johannes Weiner <hannes@cmpxchg.org> - 2017-01-02 22:20 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Jan Kara <jack@suse.cz> - 2017-01-03 13:30 +0100
              Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 07:30 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-22 18:30 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Thomas Gleixner <tglx@linutronix.de> - 2016-12-22 21:30 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 21:50 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 22:10 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-22 22:20 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 23:20 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 23:40 +0100
                Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-23 05:00 +0100
          Re: [4.10, panic, regression] iscsi: null pointer deref at         iscsi_tcp_segment_done+0x20d/0x2e0 Christoph Hellwig <hch@lst.de> - 2016-12-22 07:20 +0100
            Re: [4.10, panic, regression] iscsi: null pointer deref at  iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner <david@fromorbit.com> - 2016-12-22 07:40 +0100
              Re: [4.10, panic, regression] iscsi: null pointer deref at         iscsi_tcp_segment_done+0x20d/0x2e0 Christoph Hellwig <hch@lst.de> - 2016-12-22 07:40 +0100

csiph-web