io_uring/kbuf: use WRITE_ONCE() for userspace-shared buffer ring fields

buf->addr and buf->len reside in memory shared with userspace. They
should be written with WRITE_ONCE() to guarantee atomic stores and
prevent tearing or other unsafe compiler optimizations.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Cc: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 52b636d00a6b23bdfd6d62e04ebc87ff3f4db8db..796d131107ddb955b324d98d613d65e4e90f1840 100644 (file)
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -44,11 +44,11 @@ static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len)
                buf_len -= this_len;
                /* Stop looping for invalid buffer length of 0 */
                if (buf_len || !this_len) {
-                       buf->addr = READ_ONCE(buf->addr) + this_len;
-                       buf->len = buf_len;
+                       WRITE_ONCE(buf->addr, READ_ONCE(buf->addr) + this_len);
+                       WRITE_ONCE(buf->len, buf_len);
                        return false;
                }
-               buf->len = 0;
+               WRITE_ONCE(buf->len, 0);
                bl->head++;
                len -= this_len;
        }
@@ -291,7 +291,7 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
                                arg->partial_map = 1;
                                if (iov != arg->iovs)
                                        break;
-                               buf->len = len;
+                               WRITE_ONCE(buf->len, len);
                        }
                }