On Mon, Dec 14, 2020 at 12:19 PM Maciej Fijalkowski
<maciej.fijalkowski@xxxxxxxxx> wrote:
>
> On Mon, Dec 14, 2020 at 09:51:27AM +0100, Magnus Karlsson wrote:
> > From: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> >
> > Fix a possible memory leak when a bind of an AF_XDP socket fails. When
> > the fill and completion rings are created, they are tied to the
> > socket. But when the buffer pool is later created at bind time, the
> > ownership of these two rings are transferred to the buffer pool as
> > they might be shared between sockets (and the buffer pool cannot be
> > created until we know what we are binding to). So, before the buffer
> > pool is created, these two rings are cleaned up with the socket, and
> > after they have been transferred they are cleaned up together with
> > the buffer pool.
> >
> > The problem is that ownership was transferred before it was absolutely
> > certain that the buffer pool could be created and initialized
> > correctly and when one of these errors occurred, the fill and
> > completion rings did neither belong to the socket nor the pool and
> > where therefore leaked. Solve this by moving the ownership transfer
> > to the point where the buffer pool has been completely set up and
> > there is no way it can fail.
> >
> > Fixes: 7361f9c3d719 ("xsk: Move fill and completion rings to buffer pool")
> > Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> > Reported-by: syzbot+cfa88ddd0655afa88763@xxxxxxxxxxxxxxxxxxxxxxxxx
> > ---
> > net/xdp/xsk.c | 4 ++++
> > net/xdp/xsk_buff_pool.c | 2 --
> > 2 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index 62504471fd20..189cfbbcccc0 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -772,6 +772,10 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
> > }
> > }
> >
> > + /* FQ and CQ are now owned by the buffer pool and cleaned up with it. */
> > + xs->fq_tmp = NULL;
> > + xs->cq_tmp = NULL;
> > +
> > xs->dev = dev;
> > xs->zc = xs->umem->zc;
> > xs->queue_id = qid;
> > diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> > index d5adeee9d5d9..46c2ae7d91d1 100644
> > --- a/net/xdp/xsk_buff_pool.c
> > +++ b/net/xdp/xsk_buff_pool.c
> > @@ -75,8 +75,6 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
> >
> > pool->fq = xs->fq_tmp;
> > pool->cq = xs->cq_tmp;
> > - xs->fq_tmp = NULL;
> > - xs->cq_tmp = NULL;
>
> Given this change, are there any circumstances that we could hit
> xsk_release with xs->{f,c}q_tmp != NULL ?
Yes, if the user has not registered any fill or completion ring and
the socket is torn down.
> >
> > for (i = 0; i < pool->free_heads_cnt; i++) {
> > xskb = &pool->heads[i];
> >
> > base-commit: d9838b1d39283c1200c13f9076474c7624b8ec34
> > --
> > 2.29.0
> >
