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

[Greg KH <gregkh@linuxfoundation.org>]

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 :)

thanks,

greg k-h