io_uring/uring_cmd: ensure that device supports IOPOLL

commit 03b3d6be73e81ddb7c2930d942cdd17f4cfd5ba5 upstream.

It's possible for a file type to support uring commands, but not
pollable ones. Hence before issuing one of those, we should check
that it is supported and error out upfront if it isn't.

Cc: stable@vger.kernel.org
Fixes: 5756a3a7e713 ("io_uring: add iopoll infrastructure for io_uring_cmd")
Link: https://github.com/axboe/liburing/issues/816
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index e50de0b..18dfc5f 100644 (file)
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -108,7 +108,7 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
        struct file *file = req->file;
        int ret;
 
-       if (!req->file->f_op->uring_cmd)
+       if (!file->f_op->uring_cmd)
                return -EOPNOTSUPP;
 
        ret = security_uring_cmd(ioucmd);
@@ -120,6 +120,8 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
        if (ctx->flags & IORING_SETUP_CQE32)
                issue_flags |= IO_URING_F_CQE32;
        if (ctx->flags & IORING_SETUP_IOPOLL) {
+               if (!file->f_op->uring_cmd_iopoll)
+                       return -EOPNOTSUPP;
                issue_flags |= IO_URING_F_IOPOLL;
                req->iopoll_completed = 0;
                WRITE_ONCE(ioucmd->cookie, NULL);