Re: [PATCH v1] io_uring: fix dangling iovec after provided-buffer bundle grow failure

[Jens Axboe]

On 7/6/26 11:46 AM, Hao-Yu Yang wrote:
> On Mon, Jul 06, 2026 at 11:39:14AM -0600, Jens Axboe wrote:
>> On 7/6/26 11:34 AM, Hao-Yu Yang wrote:
>>> On Mon, Jul 06, 2026 at 11:13:55AM -0600, Jens Axboe wrote:
>>>> On 7/6/26 11:01 AM, Hao-Yu Yang wrote:
>>>>> Sorry, i forgot to cc others mail
>>>>>
>>>>> I discovered and wrote the PoC myself. Trigger way is
>>>>>  send1: Submit an IORING_OP_SEND request with four valid
>>>>>  provided buffers. The system will allocate and cache an
>>>>>  iovec array (of size 4) for this request and store the
>>>>>  pointer in kmsg->vec.iovec.
>>>>>
>>>>>  send2: Submit a second send request with 8, and I set
>>>>>  the fourth passed-in address to point to an invalid address.
>>>>>  Now kmsg still hold old iovec, but old iovec object have
>>>>>  been freed.
>>>>>
>>>>>  So this will lead dangling pointer.
>>>>
>>>> Side note: please don't top post, linux mailing lists always reply
>>>> under the text for better readability. Top posting turns any kind
>>>> of threaded conversation into both a mess, and it's also wasteful.
>>>>
>>>> Great thanks! Want to turn this into a liburing test case? Then we can
>>>> include it there as well, and it'd catch both UAF and memory leaks when
>>>> run.
>>>>
>>>> -- 
>>>> Jens Axboe
>>>
>>> How to turn this into a liburing test case? Should this be included in
>>> the v2 patch?
>>
>> Look at the tests in test/ in liburing. Or just send the reproducer and
>> I can get it turned into a test case.
>>
>> Should be separate from a kernel patch, it's a patch for an entirely
>> different repository.
>>
>>
>> -- 
>> Jens Axboe
> 
> OK, I will send v2 patch first when i wake up. And I now my PoC to
> trigger this KASAN have became a exploit can use to priviledge
> escalation. I think i should send this script to your email? (not
> included any public gmail?)

Like I said in my original reply, there's no security concerns here, as
the code in question is NOT IN A RELEASED kernel. It only exists in the
7.2-rc kernels, and the kernel documentation will tell you that unless
it's in a released kernel, it's not a security issue.

-- 
Jens Axboe