The io_futex_data is allocated upfront and assigned to the io_kiocb async_data field, but the request isn't marked with REQ_F_ASYNC_DATA at that point. Those two should always go together, as the flag tells io_uring whether the field is valid or not.

Additionally, on failure cleanup, the futex handler frees the data but does not clear ->async_data. Clear the data and the flag in the error path as well.

Thanks to Trend Micro Zero Day Initiative and particularly ReDress for reporting this.

Cc: stable@vger.kernel.org Fixes: 194bb58c6090 ("io_uring: add support for futex wake and wait") Signed-off-by: Jens Axboe axboe@kernel.dk --- io_uring/futex.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/io_uring/futex.c b/io_uring/futex.c index 692462d50c8c..9113a44984f3 100644 --- a/io_uring/futex.c +++ b/io_uring/futex.c @@ -288,6 +288,7 @@ int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags) goto done_unlock; }

+ req->flags |= REQ_F_ASYNC_DATA; req->async_data = ifd; ifd->q = futex_q_init; ifd->q.bitset = iof->futex_mask; @@ -309,6 +310,8 @@ int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags) if (ret < 0) req_set_fail(req); io_req_set_res(req, ret, 0); + req->async_data = NULL; + req->flags &= ~REQ_F_ASYNC_DATA; kfree(ifd); return IOU_COMPLETE; }