From: Jens Axboe axboe@kernel.dk
Commit cac9e4418f4cbd548ccb065b3adcafe073f7f7d2 upstream.
If the application sets ->msg_control and we have to later retry this command, or if it got queued with IOSQE_ASYNC to begin with, then we need to retain the original msg_control value. This is due to the net stack overwriting this field with an in-kernel pointer, to copy it in. Hitting that path for the second time will now fail the copy from user, as it's attempting to copy from a non-user address.
Cc: stable@vger.kernel.org # 5.10+ Link: https://github.com/axboe/liburing/issues/880 Reported-and-tested-by: Marek Majkowski marek@cloudflare.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -581,6 +581,7 @@ struct io_sr_msg { size_t len; size_t done_io; struct io_buffer *kbuf; + void __user *msg_control; };
struct io_open { @@ -4718,10 +4719,16 @@ static int io_setup_async_msg(struct io_ static int io_sendmsg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg) { + struct io_sr_msg *sr = &req->sr_msg; + int ret; + iomsg->msg.msg_name = &iomsg->addr; iomsg->free_iov = iomsg->fast_iov; - return sendmsg_copy_msghdr(&iomsg->msg, req->sr_msg.umsg, + ret = sendmsg_copy_msghdr(&iomsg->msg, req->sr_msg.umsg, req->sr_msg.msg_flags, &iomsg->free_iov); + /* save msg_control as sys_sendmsg() overwrites it */ + sr->msg_control = iomsg->msg.msg_control; + return ret; }
static int io_sendmsg_prep_async(struct io_kiocb *req) @@ -4778,6 +4785,8 @@ static int io_sendmsg(struct io_kiocb *r if (ret) return ret; kmsg = &iomsg; + } else { + kmsg->msg.msg_control = sr->msg_control; }
flags = req->sr_msg.msg_flags;