On Wed, Oct 06, 2021 at 07:50:29PM +0000, Ramji Jiyani wrote:
Commit f5cb779ba163 ("ANDROID: binder: remove waitqueue when thread exits.") fixed the use-after-free in eventpoll but aio still has the same issue because it doesn't honor the POLLFREE flag.
Add support for the POLLFREE flag to force complete iocb inline in aio_poll_wake(). A thread may use it to signal it's exit and/or request to cleanup while pending poll request. In this case, aio_poll_wake() needs to make sure it doesn't keep any reference to the queue entry before returning from wake to avoid possible use after free via poll_cancel() path.
The POLLFREE flag is no more exclusive to the epoll and is being shared with the aio. Remove comment from poll.h to avoid confusion.
This fixes a use after free issue between binder thread and aio interactions in certain sequence of events [1].
[1] https://lore.kernel.org/all/CAKUd0B_TCXRY4h1hTztfwWbNSFQqsudDLn2S_28csgWZmZA...
Signed-off-by: Ramji Jiyani ramjiyani@google.com Reviewed-by: Jeff Moyer jmoyer@redhat.com
Can you add Fixes and Cc stable tags to ensure that this fix gets backported? Please refer to Documentation/process/submitting-patches.rst.
- Eric