Re: FAILED: patch "[PATCH] io_uring: fix race in unified task_work running" failed to apply to 5.13-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Sat, Jul 31, 2021 at 08:44:33AM -0600, Jens Axboe wrote:
> On 7/31/21 12:43 AM, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 5.13-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> 
> Here's a tested 5.13-stable port.
> 
> From: Jens Axboe <axboe@kernel.dk>
> Subject: io_uring: fix race in unified task_work running
> 
> commit 110aa25c3ce417a44e35990cf8ed22383277933a upstream.
> 
> We use a bit to manage if we need to add the shared task_work, but
> a list + lock for the pending work. Before aborting a current run
> of the task_work we check if the list is empty, but we do so without
> grabbing the lock that protects it. This can lead to races where
> we think we have nothing left to run, where in practice we could be
> racing with a task adding new work to the list. If we do hit that
> race condition, we could be left with work items that need processing,
> but the shared task_work is not active.
> 
> Ensure that we grab the lock before checking if the list is empty,
> so we know if it's safe to exit the run or not.
> 
> Link: https://lore.kernel.org/io-uring/c6bd5987-e9ae-cd02-49d0-1b3ac1ef65b1@tnonline.net/
> Cc: stable@vger.kernel.org # 5.11+
> Reported-by: Forza <forza@tnonline.net>
> Tested-by: Forza <forza@tnonline.net>

Now queued up, thanks!

greg k-h