Re: [PATCH Next] iomap: Add sanity check for dio done workqueue

[Christoph Hellwig]

On Mon, Nov 24, 2025 at 04:53:04PM +0800, Edward Adam Davis wrote:
> The s_dio_done_wq was not allocated memory, leading to the null-ptr-deref
> reported by syzbot in [1].
> 
> As shown in [1], we are currently in a soft interrupt context, and we cannot
> use sb_init_dio_done_wq() to allocate memory for wq because it requires a
> mutex lock.
> 
> Added a check to the workqueue; if it is empty, it switches to using a
> synchronous method to end the dio.

Err no.  That sanity check doesn't do anything useful.  Whatever caused
it to be not allocated and allow I/O needs to be fixed.  And I suspect
it's my fault and I already have an idea how to fix, so don't rush it.