Re: [PATCH 6.1] io_uring: fix possible deadlock in io_register_iowq_max_workers()

[Jens Axboe <axboe@kernel.dk>]

On 11/12/24 1:39 AM, Greg KH wrote:
> On Tue, Nov 12, 2024 at 08:30:06AM +0000, Hagar Hemdan wrote:
>> commit 73254a297c2dd094abec7c9efee32455ae875bdf upstream.
>>
>> The io_register_iowq_max_workers() function calls io_put_sq_data(),
>> which acquires the sqd->lock without releasing the uring_lock.
>> Similar to the commit 009ad9f0c6ee ("io_uring: drop ctx->uring_lock
>> before acquiring sqd->lock"), this can lead to a potential deadlock
>> situation.
>>
>> To resolve this issue, the uring_lock is released before calling
>> io_put_sq_data(), and then it is re-acquired after the function call.
>>
>> This change ensures that the locks are acquired in the correct
>> order, preventing the possibility of a deadlock.
>>
>> Suggested-by: Maximilian Heyne <mheyne@amazon.de>
>> Signed-off-by: Hagar Hemdan <hagarhem@amazon.com>
>> Link: https://lore.kernel.org/r/20240604130527.3597-1-hagarhem@amazon.com
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> [Hagar: Modified to apply on v6.1]
>> Signed-off-by: Hagar Hemdan <hagarhem@amazon.com>
>> ---
>>  io_uring/io_uring.c | 5 +++++
>>  1 file changed, 5 insertions(+)
> 
> What about 6.6.y?  We can't just take patches for older branches and not
> newer ones, you know this :)

Hagar, thanks for doing the other ones too. Greg, they look fine to me.

-- 
Jens Axboe