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 07:56:45AM -0700, Jens Axboe wrote:
> 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.

Thanks, all now queued up.

greg k-h