Re: [PATCH for-rc] RDMA/core: Call dev_put after query_port in iw_query_port

[Guoqing Jiang <guoqing.jiang@linux.dev>]

On 5/19/23 22:05, Chuck Lever III wrote:
>
>> On May 19, 2023, at 10:03 AM, Jason Gunthorpe <jgg@ziepe.ca> wrote:
>>
>> On Fri, May 19, 2023 at 11:11:19AM +0800, Guoqing Jiang wrote:
>>> There is a UAF report by syzbot.
>>>
>>> BUG: KASAN: slab-use-after-free in siw_query_port+0x37b/0x3e0 drivers/infiniband/sw/siw/siw_verbs.c:177
>>> Read of size 4 at addr ffff888034efa0e8 by task kworker/1:4/24211
>>>
>>> CPU: 1 PID: 24211 Comm: kworker/1:4 Not tainted 6.4.0-rc1-syzkaller-00012-g16a8829130ca #0
>>> Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
>>> Workqueue: infiniband ib_cache_event_task
>>> Call Trace:
>>> <TASK>
>>> __dump_stack lib/dump_stack.c:88 [inline]
>>> dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
>>> print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
>>> print_report mm/kasan/report.c:462 [inline]
>>> kasan_report+0x11c/0x130 mm/kasan/report.c:572
>>> siw_query_port+0x37b/0x3e0 drivers/infiniband/sw/siw/siw_verbs.c:177
>>> iw_query_port drivers/infiniband/core/device.c:2049 [inline]
>>> ib_query_port drivers/infiniband/core/device.c:2090 [inline]
>>> ib_query_port+0x3c4/0x8f0 drivers/infiniband/core/device.c:2082
>>> ib_cache_update.part.0+0xcf/0x920 drivers/infiniband/core/cache.c:1487
>>> ib_cache_update drivers/infiniband/core/cache.c:1561 [inline]
>>> ib_cache_event_task+0x1b1/0x270 drivers/infiniband/core/cache.c:1561
>>> process_one_work+0x99a/0x15e0 kernel/workqueue.c:2405
>>> worker_thread+0x67d/0x10c0 kernel/workqueue.c:2552
>>> kthread+0x344/0x440 kernel/kthread.c:379
>>> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
>>> </TASK>
>>>
>>> It happened because netdev could be freed if the last reference
>>> is released, but drivers still dereference netdev in query_port.
>>> So let's guard query_port with dev_hold and dev_put.
>>>
>>> Reported-by: syzbot+79f283f1f4ccc6e8b624@syzkaller.appspotmail.com
>>> Closes: https://lore.kernel.org/lkml/0000000000001f992805fb79ce97@google.com/
>>> Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
>>> ---
>>> I guess another option could be call ib_device_get_netdev to get
>>> netdev in siw_query_port instead of dereference netdev directly.
>>> If so, then other drivers (irdma_query_port and ocrdma_query_port)
>>> may need to make relevant change as well.
>> Something is wrong in siw if it is UAF'ing it's own memory:
>>
>> attr->max_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
>>
>> It needs to protect sedv->netdev somehow on its own.
> Note that netdev is actually the underlying device. An siw device
> doesn't have its own. But maybe it should.

I go through siw code a bit, and can't find relevant protection in siw.
Let me cc Bernard.

Thanks,
Guoqing