Re: [PATCH v2] io_uring: fix dead-hung for non-iter fixed rw

[Jens Axboe <axboe@kernel.dk>]

On 11/24/19 5:43 PM, Jackie Liu wrote:
> 
> 
>> 2019年11月25日 01:52，Pavel Begunkov <asml.silence@gmail.com> 写道：
>>
>> On 24/11/2019 20:10, Jens Axboe wrote:
>>> On 11/24/19 1:58 AM, Pavel Begunkov wrote:
>>>> Read/write requests to devices without implemented read/write_iter
>>>> using fixed buffers causes general protection fault, which totally
>>>> hangs a machine.
>>>>
>>>> io_import_fixed() initialises iov_iter with bvec, but loop_rw_iter()
>>>> accesses it as iovec, so dereferencing random address.
>>>>
>>>> kmap() page by page in this case
>>>
>>> This looks good to me, much cleaner/simpler. I've added a few pipe fixed
>>> buffer tests to liburing as well. Didn't crash for me, but obvious
>>> garbage coming out. I've flagged this for stable as well.
>>>
>> The problem I have is that __user pointer is meant to be checked
>> for not being a kernel address. I suspect, it could fail in some
>> device, which double checks the pointer after vfs (e.g. using access_ok()).
>> Am I wrong? Not a fault at least...
>>
>> #define access_ok(...) __range_not_ok(addr, user_addr_max());
>>
>> BTW, is there anybody testing it for non x86-64 arch?
>>
> 
> I have some aarch64 platform, What test do you want me to do?

A basic one to try would be:

axboe@x1:/home/axboe/git/liburing $ test/stdout 
This is a pipe test
This is a fixed pipe test

But in general I'd just run make runtests in the liburing directory
and go through all of them.

-- 
Jens Axboe