linux-kernel - Re: [PATCH rdma-rc] RDMA/cma: Clear all multicast request fields

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Date:   Sun, 9 Jan 2022 14:22:04 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        syzbot+8fcbb77276d43cc8b693@...kaller.appspotmail.com
Subject: Re: [PATCH rdma-rc] RDMA/cma: Clear all multicast request fields

On Thu, Jan 06, 2022 at 01:39:41PM -0400, Jason Gunthorpe wrote:
> On Thu, Jan 06, 2022 at 03:15:07PM +0200, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> > 
> > The ib->rec.qkey field is accessed without being initialized.
> > Clear the ib_sa_multicast struct to fix the following syzkaller error/.
> > 
> > =====================================================
> > BUG: KMSAN: uninit-value in cma_set_qkey drivers/infiniband/core/cma.c:510 [inline]
> > BUG: KMSAN: uninit-value in cma_make_mc_event+0xb73/0xe00 drivers/infiniband/core/cma.c:4570
> >  cma_set_qkey drivers/infiniband/core/cma.c:510 [inline]
> >  cma_make_mc_event+0xb73/0xe00 drivers/infiniband/core/cma.c:4570
> >  cma_iboe_join_multicast drivers/infiniband/core/cma.c:4782 [inline]
> >  rdma_join_multicast+0x2b83/0x30a0 drivers/infiniband/core/cma.c:4814
> >  ucma_process_join+0xa76/0xf60 drivers/infiniband/core/ucma.c:1479
> >  ucma_join_multicast+0x1e3/0x250 drivers/infiniband/core/ucma.c:1546
> >  ucma_write+0x639/0x6d0 drivers/infiniband/core/ucma.c:1732
> >  vfs_write+0x8ce/0x2030 fs/read_write.c:588
> >  ksys_write+0x28c/0x520 fs/read_write.c:643
> >  __do_sys_write fs/read_write.c:655 [inline]
> >  __se_sys_write fs/read_write.c:652 [inline]
> >  __ia32_sys_write+0xdb/0x120 fs/read_write.c:652
> >  do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
> >  __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
> >  do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
> >  do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
> >  entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
> > 
> > Local variable ib.i created at:
> >  cma_iboe_join_multicast drivers/infiniband/core/cma.c:4737 [inline]
> >  rdma_join_multicast+0x586/0x30a0 drivers/infiniband/core/cma.c:4814
> >  ucma_process_join+0xa76/0xf60 drivers/infiniband/core/ucma.c:1479
> > 
> > CPU: 0 PID: 29874 Comm: syz-executor.3 Not tainted 5.16.0-rc3-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > =====================================================
> > 
> > Fixes: b5de0c60cc30 ("RDMA/cma: Fix use after free race in roce multicast join")
> > Reported-by: syzbot+8fcbb77276d43cc8b693@...kaller.appspotmail.com
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> >  drivers/infiniband/core/cma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> > index 69c9a12dd14e..9c53e1e7de50 100644
> > +++ b/drivers/infiniband/core/cma.c
> > @@ -4737,7 +4737,7 @@ static int cma_iboe_join_multicast(struct rdma_id_private *id_priv,
> >  	int err = 0;
> >  	struct sockaddr *addr = (struct sockaddr *)&mc->addr;
> >  	struct net_device *ndev = NULL;
> > -	struct ib_sa_multicast ib;
> > +	struct ib_sa_multicast ib = {};
> >  	enum ib_gid_type gid_type;
> >  	bool send_only;
> 
> We shouldn't be able to join anything except a RDMA_PS_UDP to a
> multicast in the first place:
> 
> 	if (id_priv->id.ps == RDMA_PS_UDP)
> 		ib.rec.qkey = cpu_to_be32(RDMA_UDP_QKEY);
> 
> Multicast RC/etc is meaningless. So I guess it should be like this:

I don't know, I used 0 exactly like we have for cma_join_ib_multicast().

Where can I read about this PS limitation? I didn't find anything
relevant in the IBTA spec.

Thanks