Re: [PATCH 5.13] io_uring: Check current->io_uring in io_uring_cancel_sqpoll

On 4/27/21 6:51 AM, Palash Oswal wrote:

syzkaller identified KASAN: null-ptr-deref Write in io_uring_cancel_sqpoll on v5.12

io_uring_cancel_sqpoll is called by io_sq_thread before calling io_uring_alloc_task_context. This leads to current->io_uring being NULL. io_uring_cancel_sqpoll should not have to deal with threads where current->io_uring is NULL.

In order to cast a wider safety net, perform input sanitisation directly in io_uring_cancel_sqpoll and return for NULL value of current->io_uring.

Thanks applied - I augmented the commit message a bit.