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 09bb82bc209a10e7277ec19909fb816834222c56..a70bbd4bd7cb420f77eac02082949321b6c6054f 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1116,6 +1116,7 @@ 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))
@@ -1170,6 +1171,7 @@ out_free:
                req_set_fail(req);
        }
 
+       mshot_finished = ret <= 0;
        if (ret > 0)
                ret += sr->done_io;
        else if (sr->done_io)
@@ -1177,7 +1179,7 @@ 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;