[Xen-devel] [RFC PATCH 11/60] hyper_dmabuf: check stack before unmapping/detaching shadow DMA_BUF

[Dongwon Kim <dongwon.kim@xxxxxxxxx>]

Make sure list of mapping/attaching activities on impoter VM is not
empty before doing unmapping/detaching shadow DMA BUF for indirect
synchronization.

Signed-off-by: Dongwon Kim <dongwon.kim@xxxxxxxxx>
---
 .../xen/hyper_dmabuf/hyper_dmabuf_remote_sync.c    | 68 +++++++++++++++++-----
 1 file changed, 53 insertions(+), 15 deletions(-)

diff --git a/drivers/xen/hyper_dmabuf/hyper_dmabuf_remote_sync.c 
b/drivers/xen/hyper_dmabuf/hyper_dmabuf_remote_sync.c
index 6ba932f..fa2fa11 100644
--- a/drivers/xen/hyper_dmabuf/hyper_dmabuf_remote_sync.c
+++ b/drivers/xen/hyper_dmabuf/hyper_dmabuf_remote_sync.c
@@ -11,6 +11,21 @@
 
 extern struct hyper_dmabuf_private hyper_dmabuf_private;
 
+/* Whenever importer does dma operations from remote domain,
+ * a notification is sent to the exporter so that exporter
+ * issues equivalent dma operation on the original dma buf
+ * for indirect synchronization via shadow operations.
+ *
+ * All ptrs and references (e.g struct sg_table*,
+ * struct dma_buf_attachment) created via these operations on
+ * exporter's side are kept in stack (implemented as circular
+ * linked-lists) separately so that those can be re-referenced
+ * later when unmapping operations are invoked to free those.
+ *
+ * The very first element on the bottom of each stack holds
+ * are what is created when initial exporting is issued so it
+ * should not be modified or released by this fuction.
+ */
 int hyper_dmabuf_remote_sync(int id, int ops)
 {
        struct hyper_dmabuf_sgt_info *sgt_info;
@@ -33,7 +48,7 @@ int hyper_dmabuf_remote_sync(int id, int ops)
                attachl = kcalloc(1, sizeof(*attachl), GFP_KERNEL);
 
                attachl->attach = dma_buf_attach(sgt_info->dma_buf,
-                                               hyper_dmabuf_private.device);
+                                                hyper_dmabuf_private.device);
 
                if (!attachl->attach) {
                        kfree(attachl);
@@ -45,22 +60,31 @@ int hyper_dmabuf_remote_sync(int id, int ops)
                break;
 
        case HYPER_DMABUF_OPS_DETACH:
-               attachl = list_first_entry(&sgt_info->active_attached->list,
-                                       struct attachment_list, list);
-
-               if (!attachl) {
+               if (list_empty(&sgt_info->active_attached->list)) {
                        printk("dmabuf remote sync::error while processing 
HYPER_DMABUF_OPS_DETACH\n");
+                       printk("no more dmabuf attachment left to be 
detached\n");
                        return -EINVAL;
                }
+
+               attachl = list_first_entry(&sgt_info->active_attached->list,
+                                          struct attachment_list, list);
+
                dma_buf_detach(sgt_info->dma_buf, attachl->attach);
                list_del(&attachl->list);
                kfree(attachl);
                break;
 
        case HYPER_DMABUF_OPS_MAP:
-               sgtl = kcalloc(1, sizeof(*sgtl), GFP_KERNEL);
+               if (list_empty(&sgt_info->active_attached->list)) {
+                       printk("dmabuf remote sync::error while processing 
HYPER_DMABUF_OPS_MAP\n");
+                       printk("no more dmabuf attachment left to be 
detached\n");
+                       return -EINVAL;
+               }
+
                attachl = list_first_entry(&sgt_info->active_attached->list,
-                                       struct attachment_list, list);
+                                          struct attachment_list, list);
+
+               sgtl = kcalloc(1, sizeof(*sgtl), GFP_KERNEL);
                sgtl->sgt = dma_buf_map_attachment(attachl->attach, 
DMA_BIDIRECTIONAL);
                if (!sgtl->sgt) {
                        kfree(sgtl);
@@ -71,17 +95,20 @@ int hyper_dmabuf_remote_sync(int id, int ops)
                break;
 
        case HYPER_DMABUF_OPS_UNMAP:
-               attachl = list_first_entry(&sgt_info->active_attached->list,
-                                       struct attachment_list, list);
-               sgtl = list_first_entry(&sgt_info->active_sgts->list,
-                                       struct sgt_list, list);
-               if (!attachl || !sgtl) {
+               if (list_empty(&sgt_info->active_sgts->list) ||
+                   list_empty(&sgt_info->active_attached->list)) {
                        printk("dmabuf remote sync::error while processing 
HYPER_DMABUF_OPS_UNMAP\n");
+                       printk("no more SGT or attachment left to be freed\n");
                        return -EINVAL;
                }
 
+               attachl = list_first_entry(&sgt_info->active_attached->list,
+                                          struct attachment_list, list);
+               sgtl = list_first_entry(&sgt_info->active_sgts->list,
+                                       struct sgt_list, list);
+
                dma_buf_unmap_attachment(attachl->attach, sgtl->sgt,
-                                       DMA_BIDIRECTIONAL);
+                                        DMA_BIDIRECTIONAL);
                list_del(&sgtl->list);
                kfree(sgtl);
                break;
@@ -129,9 +156,15 @@ int hyper_dmabuf_remote_sync(int id, int ops)
 
        case HYPER_DMABUF_OPS_KUNMAP_ATOMIC:
        case HYPER_DMABUF_OPS_KUNMAP:
+               if (list_empty(&sgt_info->va_kmapped->list)) {
+                       printk("dmabuf remote sync::error while processing 
HYPER_DMABUF_OPS_KUNMAP(_ATOMIC)\n");
+                       printk("no more dmabuf VA to be freed\n");
+                       return -EINVAL;
+               }
+
                va_kmapl = list_first_entry(&sgt_info->va_kmapped->list,
-                                       struct kmap_vaddr_list, list);
-               if (!va_kmapl || va_kmapl->vaddr == NULL) {
+                                           struct kmap_vaddr_list, list);
+               if (va_kmapl->vaddr == NULL) {
                        printk("dmabuf remote sync::error while processing 
HYPER_DMABUF_OPS_KUNMAP(_ATOMIC)\n");
                        return -EINVAL;
                }
@@ -167,6 +200,11 @@ int hyper_dmabuf_remote_sync(int id, int ops)
                break;
 
        case HYPER_DMABUF_OPS_VUNMAP:
+               if (list_empty(&sgt_info->va_vmapped->list)) {
+                       printk("dmabuf remote sync::error while processing 
HYPER_DMABUF_OPS_VUNMAP\n");
+                       printk("no more dmabuf VA to be freed\n");
+                       return -EINVAL;
+               }
                va_vmapl = list_first_entry(&sgt_info->va_vmapped->list,
                                        struct vmap_vaddr_list, list);
                if (!va_vmapl || va_vmapl->vaddr == NULL) {
-- 
2.7.4


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