xen: fix ioreq handling

Avoid double fetches and bounds check size to avoid overflowing
internal variables.

This is XSA-197.

Reported-by: yanghongke <yanghongke@huawei.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/xen-all.c b/xen-all.c
index 984c34613cc1eae09cf1c240dedc09d3d09c7405..178576aabfe0813b4c98d42535054b43c0443c4e 100644 (file)
--- a/xen-all.c
+++ b/xen-all.c
@@ -714,6 +714,10 @@ static void cpu_ioreq_pio(ioreq_t *req)
 {
     uint32_t i;
 
+    if (req->size > sizeof(uint32_t)) {
+        hw_error("PIO: bad size (%u)", req->size);
+    }
+
     if (req->dir == IOREQ_READ) {
         if (!req->data_is_ptr) {
             req->data = do_inp(req->addr, req->size);
@@ -743,6 +747,10 @@ static void cpu_ioreq_move(ioreq_t *req)
 {
     uint32_t i;
 
+    if (req->size > sizeof(req->data)) {
+        hw_error("MMIO: bad size (%u)", req->size);
+    }
+
     if (!req->data_is_ptr) {
         if (req->dir == IOREQ_READ) {
             for (i = 0; i < req->count; i++) {
@@ -818,11 +826,13 @@ static int handle_buffered_iopage(XenIOState *state)
         req.df = 1;
         req.type = buf_req->type;
         req.data_is_ptr = 0;
+        xen_rmb();
         qw = (req.size == 8);
         if (qw) {
             buf_req = &state->buffered_io_page->buf_ioreq[
                 (state->buffered_io_page->read_pointer + 1) % IOREQ_BUFFER_SLOT_NUM];
             req.data |= ((uint64_t)buf_req->data) << 32;
+            xen_rmb();
         }
 
         handle_ioreq(&req);
@@ -854,7 +864,11 @@ static void cpu_handle_ioreq(void *opaque)
 
     handle_buffered_iopage(state);
     if (req) {
-        handle_ioreq(req);
+        ioreq_t copy = *req;
+
+        xen_rmb();
+        handle_ioreq(&copy);
+        req->data = copy.data;
 
         if (req->state != STATE_IOREQ_INPROCESS) {
             fprintf(stderr, "Badness in I/O request ... not in service?!: "