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io_uring: NULL-deref for IOSQE_{ASYNC,DRAIN} 

Processing links, io_submit_sqe() prepares requests, drops sqes, and
passes them with sqe=NULL to io_queue_sqe(). There IOSQE_DRAIN and/or
IOSQE_ASYNC requests will go through the same prep, which doesn't expect
sqe=NULL and fail with NULL pointer deference.

Always do full prepare including io_alloc_async_ctx() for linked
requests, and then it can skip the second preparation.

Cc: stable@vger.kernel.org # 5.5
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2020-03-13 22:29:14 +03:00 committed by Jens Axboe
parent 805b13adde
commit f1d96a8fcb
1 changed files with 8 additions and 0 deletions
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8
fs/io_uring.c
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@ -4131,6 +4131,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
{
ssize_t ret = 0;
if (!sqe)
return 0;
if (io_op_defs[req->opcode].file_table) {
ret = io_grab_files(req);
if (unlikely(ret))
@ -4907,6 +4910,11 @@ err_req:
if (sqe_flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)) {
req->flags |= REQ_F_LINK;
INIT_LIST_HEAD(&req->link_list);
if (io_alloc_async_ctx(req)) {
ret = -EAGAIN;
goto err_req;
}
ret = io_req_defer_prep(req, sqe);
if (ret)
req->flags |= REQ_F_FAIL_LINK;