io_uring/net: harden multishot termination case for recv

commit c314094cb4cfa6fc5a17f4881ead2dfebfa717a7 upstream.

If the recv returns zero, or an error, then it doesn't matter if more
data has already been received for this buffer. A condition like that
should terminate the multishot receive. Rather than pass in the
collected return value, pass in whether to terminate or keep the recv
going separately.

Note that this isn't a bug right now, as the only way to get there is
via setting MSG_WAITALL with multishot receive. And if an application
does that, then -EINVAL is returned anyway. But it seems like an easy
bug to introduce, so let's make it a bit more explicit.

Link: https://github.com/axboe/liburing/issues/1246
Cc: stable@vger.kernel.org
Fixes: b3fdea6ecb55 ("io_uring: multishot recv")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/io_uring/net.c b/io_uring/net.c
index d08abcca89cc5b7d5c605f56c69e09f8d973f458..ab2b9f172705f2338b0a25067f44815f095a2d22 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1126,6 +1126,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
        int ret, min_ret = 0;
        bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
        size_t len = sr->len;
+       bool mshot_finished;
 
        if (!(req->flags & REQ_F_POLLED) &&
            (sr->flags & IORING_RECVSEND_POLL_FIRST))
@@ -1180,6 +1181,7 @@ out_free:
                req_set_fail(req);
        }
 
+       mshot_finished = ret <= 0;
        if (ret > 0)
                ret += sr->done_io;
        else if (sr->done_io)
@@ -1187,7 +1189,7 @@ out_free:
        else
                io_kbuf_recycle(req, issue_flags);
 
-       if (!io_recv_finish(req, &ret, kmsg, ret <= 0, issue_flags))
+       if (!io_recv_finish(req, &ret, kmsg, mshot_finished, issue_flags))
                goto retry_multishot;
 
        return ret;