RE: [RDMA bug] KASAN: use-after-free Read in __list_del_entry_valid (4)

[Parav Pandit]

> -----Original Message-----
> From: Jason Gunthorpe <jgg@xxxxxxxx>
> Sent: Thursday, August 23, 2018 9:55 AM
> To: Eric Biggers <ebiggers@xxxxxxxxxx>
> Cc: Doug Ledford <dledford@xxxxxxxxxx>; linux-rdma@xxxxxxxxxxxxxxx;
> dasaratharaman.chandramouli@xxxxxxxxx; Leon Romanovsky
> <leonro@xxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Mark Bloch
> <markb@xxxxxxxxxxxx>; Moni Shoua <monis@xxxxxxxxxxxx>; Parav Pandit
> <parav@xxxxxxxxxxxx>; syzkaller-bugs@xxxxxxxxxxxxxxxx; syzbot
> <syzbot+29ee8f76017ce6cf03da@xxxxxxxxxxxxxxxxxxxxxxxxx>
> Subject: Re: [RDMA bug] KASAN: use-after-free Read in __list_del_entry_valid
> (4)
> 
> On Wed, Aug 22, 2018 at 11:16:31PM -0700, Eric Biggers wrote:
> > Hello RDMA / InfiniBand maintainers,
> >
> > This is an RDMA bug and it still occurs on Linus' tree as of today
> > (commit 815f0ddb346c1960).
> >
> > I've also simplified the reproducer for it; see below after the original report.
> > Apparently it involves a race between RDMA_USER_CM_CMD_RESOLVE_IP
> and
> > RDMA_USER_CM_CMD_LISTEN.
> 
> That is an amazing reproducer!
> 
> I have a feeling this is the same cause as all the other syzkaller bugs in this code:
> lack of any sane locking at all :\
> 
> We've talked about chucking a big lock around this whole thing, but nobody has
> done it yet.. It isn't so simple.
> 
I had some code in which reduces three locks (handler_lock, qp_mutex, id_lock) to single mutex to protect the cm_id and protects every exported symbol of rdmacm which works on cm_id.
But not ready enough to post it as patch yet. Lot of tests required before I get there and some refactor too before that.

> Jason