Re: [PATCH] RDMA/uverbs: Check port number supplied by user verbs cmds

[Jason Gunthorpe <jgunthorpe@obsidianresearch.com>]

On Tue, Jul 11, 2017 at 11:21:07PM +0000, Ismail, Mustafa wrote:
> > Subject: [PATCH] RDMA/uverbs: Check port number supplied by user verbs
> > cmds
> > 
> > Upstream commit id in the rdma.git tree: 5ecce4c9b17b
> > 
> > The ib_uverbs_create_ah() ind ib_uverbs_modify_qp() calls receive the port
> > number from user input as part of its attributes and assumes it is valid.
> > Down on the stack, that parameter is used to access kernel data structures.
> > If the value is invalid, the kernel accesses memory it should not.  To prevent
> > this, verify the port number before using it.
> > 
> > BUG: KASAN: use-after-free in ib_uverbs_create_ah+0x6d5/0x7b0 Read of
> > size 4 at addr ffff880018d67ab8 by task syz-executor/313
> > 
> > BUG: KASAN: slab-out-of-bounds in modify_qp.isra.4+0x19d0/0x1ef0 Read
> > of size 4 at addr ffff88006c40ec58 by task syz-executor/819
> > 
> > Fixes: 67cdb40ca444 ("[IB] uverbs: Implement more commands")
> > Cc: <stable@vger.kernel.org> # v4.2-v4.9
> > Cc: <security@kernel.org>
> > Cc: Yevgeny Kliteynik <kliteyn@mellanox.com>
> > Cc: Tziporet Koren <tziporet@mellanox.com>
> > Cc: Alex Polak <alexpo@mellanox.com>
> > Signed-off-by: Boris Pismenny <borisp@mellanox.com>
> > Signed-off-by: Leon Romanovsky <leon@kernel.org>
> > Signed-off-by: Doug Ledford <dledford@redhat.com>
> > 
> > Modified from upstream commit: helper function rdma_is_port_valid does
> > not exist in these kernel versions, so use manual comparisons instead.
> > 
> >  drivers/infiniband/core/uverbs_cmd.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/infiniband/core/uverbs_cmd.c
> > b/drivers/infiniband/core/uverbs_cmd.c
> > index cb3f515a2285..01e3a37b0aef 100644
> > +++ b/drivers/infiniband/core/uverbs_cmd.c
> > @@ -2342,6 +2342,10 @@ ssize_t ib_uverbs_modify_qp(struct
> > ib_uverbs_file *file,
> >  	if (copy_from_user(&cmd, buf, sizeof cmd))
> >  		return -EFAULT;
> > 
> > +	if (cmd.port_num < rdma_start_port(ib_dev) ||
> > +	    cmd.port_num > rdma_end_port(ib_dev))
> > +		return -EINVAL;
> > +
> With this check for valid port number, ucma_modify_qp_sqd() and ucma_modify_qp_err () in rdma-core may fail since qp_attr.port_num is not initialized.

Indeed. port_num should be totally ignored if not present in
attr_mask, and should not trigger EINVAL.

Jason