io_uring/msg_ring: fix missing lock on overflow for IOPOLL

Commit e12d7a46f65ae4b7d58a5e0c1cbfa825cf8d830d upstream.

If the target ring is configured with IOPOLL, then we always need to hold
the target ring uring_lock before posting CQEs. We could just grab it
unconditionally, but since we don't expect many target rings to be of this
type, make grabbing the uring_lock conditional on the ring type.

Link: https://lore.kernel.org/io-uring/Y8krlYa52%2F0YGqkg@ip-172-31-85-199.ec2.internal/
Reported-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index 825d8c5..cd922d2 100644 (file)
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -57,20 +57,30 @@ void io_msg_ring_cleanup(struct io_kiocb *req)
        msg->src_file = NULL;
 }
 
-static int io_msg_ring_data(struct io_kiocb *req)
+static int io_msg_ring_data(struct io_kiocb *req, unsigned int issue_flags)
 {
        struct io_ring_ctx *target_ctx = req->file->private_data;
        struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+       int ret;
 
        if (msg->src_fd || msg->dst_fd || msg->flags)
                return -EINVAL;
        if (target_ctx->flags & IORING_SETUP_R_DISABLED)
                return -EBADFD;
 
-       if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
-               return 0;
+       ret = -EOVERFLOW;
+       if (target_ctx->flags & IORING_SETUP_IOPOLL) {
+               if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
+                       return -EAGAIN;
+               if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
+                       ret = 0;
+               io_double_unlock_ctx(target_ctx);
+       } else {
+               if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
+                       ret = 0;
+       }
 
-       return -EOVERFLOW;
+       return ret;
 }
 
 static struct file *io_msg_grab_file(struct io_kiocb *req, unsigned int issue_flags)
@@ -175,7 +185,7 @@ int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags)
 
        switch (msg->cmd) {
        case IORING_MSG_DATA:
-               ret = io_msg_ring_data(req);
+               ret = io_msg_ring_data(req, issue_flags);
                break;
        case IORING_MSG_SEND_FD:
                ret = io_msg_send_fd(req, issue_flags);