Re: io_uring: BUG: kernel NULL pointer dereference

From: Pavel Begunkov
Date: Mon May 25 2020 - 10:12:57 EST


On 25/05/2020 16:45, Stefano Garzarella wrote:
> On Mon, May 25, 2020 at 12:30:51PM +0200, Stefano Garzarella wrote:
>>
>> I'll try to bisect, but I have some suspicions about:
>> b41e98524e42 io_uring: add per-task callback handler
>
> I confirm, the bisection ended with this:
> b41e98524e424d104aa7851d54fd65820759875a is the first bad commit
>
> I'll try to figure out what happened.

Hmm, I'd start with temporary un-union req->task_work.
Could you give it a try?


diff --git a/fs/io_uring.c b/fs/io_uring.c
index e173cea621de..cfab79254d0a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -645,7 +645,7 @@ struct io_kiocb {

struct percpu_ref *fixed_file_refs;

- union {
+ // union {
/*
* Only commands that never go async can use the below fields,
* obviously. Right now only IORING_OP_POLL_ADD uses them, and
@@ -658,7 +658,7 @@ struct io_kiocb {
struct async_poll *apoll;
};
struct io_wq_work work;
- };
+ // };
};

#define IO_PLUG_THRESHOLD 2


--
Pavel Begunkov