io_uring/net: fix sr->len for IORING_OP_RECV with MSG_WAITALL and buffers

If we use IORING_OP_RECV with provided buffers and pass in '0' as the
length of the request, the length is retrieved from the selected buffer.
If MSG_WAITALL is also set and we get a short receive, then we may hit
the retry path which decrements sr->len and increments the buffer for
a retry. However, the length is still zero at this point, which means
that sr->len now becomes huge and import_ubuf() will cap it to
MAX_RW_COUNT and subsequently return -EFAULT for the range as a whole.

Fix this by always assigning sr->len once the buffer has been selected.

Cc: stable@vger.kernel.org
Fixes: 7ba89d2af17a ("io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/net.c b/io_uring/net.c
index a12ff69e684348513335a43b105b821eb588139b..43bc9a5f96f9d1ce48f2d6e2a5cf850c675aee0d 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -923,6 +923,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
                if (!buf)
                        return -ENOBUFS;
                sr->buf = buf;
+               sr->len = len;
        }
 
        ret = import_ubuf(ITER_DEST, sr->buf, len, &msg.msg_iter);