[Linaro-mm-sig] Re: [PATCH] dmabuf: fix dmabuf file poll uaf issue

On Tue, Mar 26, 2024 at 7:29 PM Zhiguo Jiang justinjiang@vivo.com wrote:

The issue is a UAF issue of dmabuf file fd. Throght debugging, we found that the dmabuf file fd is added to the epoll event listener list, and when it is released, it is not removed from the epoll list, which leads to the UAF(Use-After-Free) issue.

The UAF issue can be solved by checking dmabuf file->f_count value and skipping the poll operation for the closed dmabuf file in the dma_buf_poll(). We have tested this solved patch multiple times and have not reproduced the uaf issue.

Hi Zhiguo,

What is the most recent kernel version you've seen the bug on?

You are closing the dmabuf fd from another thread while it is still part of the epoll interest list?

Thanks, T.J.