[PULL 03/20] qcow2: check request on vmstate save/load path

[Eric Blake <eblake@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We modify the request by adding an offset to vmstate. Let's check the
modified request. It will help us to safely move .bdrv_co_preadv_part
and .bdrv_co_pwritev_part to int64_t type of offset and bytes.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210903102807.27127-3-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/block_int.h |  3 +++
 block/io.c                |  6 +++---
 block/qcow2.c             | 43 +++++++++++++++++++++++++++++++++------
 3 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 5451f89b8df9..ed60495938a6 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -94,6 +94,9 @@ typedef struct BdrvTrackedRequest {
     struct BdrvTrackedRequest *waiting_for;
 } BdrvTrackedRequest;

+int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
+                            QEMUIOVector *qiov, size_t qiov_offset,
+                            Error **errp);
 int bdrv_check_request(int64_t offset, int64_t bytes, Error **errp);

 struct BlockDriver {
diff --git a/block/io.c b/block/io.c
index 58602f84dbf0..a4f124f75577 100644
--- a/block/io.c
+++ b/block/io.c
@@ -956,9 +956,9 @@ bool coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req,
     return waited;
 }

-static int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
-                                   QEMUIOVector *qiov, size_t qiov_offset,
-                                   Error **errp)
+int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
+                            QEMUIOVector *qiov, size_t qiov_offset,
+                            Error **errp)
 {
     /*
      * Check generic offset/bytes correctness
diff --git a/block/qcow2.c b/block/qcow2.c
index 02f9f3e63679..1c3cf7f91d86 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -5227,24 +5227,55 @@ static int qcow2_has_zero_init(BlockDriverState *bs)
     }
 }

+/*
+ * Check the request to vmstate. On success return
+ *      qcow2_vm_state_offset(bs) + @pos
+ */
+static int64_t qcow2_check_vmstate_request(BlockDriverState *bs,
+                                           QEMUIOVector *qiov, int64_t pos)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int64_t vmstate_offset = qcow2_vm_state_offset(s);
+    int ret;
+
+    /* Incoming requests must be OK */
+    bdrv_check_qiov_request(pos, qiov->size, qiov, 0, &error_abort);
+
+    if (INT64_MAX - pos < vmstate_offset) {
+        return -EIO;
+    }
+
+    pos += vmstate_offset;
+    ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return pos;
+}
+
 static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
                               int64_t pos)
 {
-    BDRVQcow2State *s = bs->opaque;
+    int64_t offset = qcow2_check_vmstate_request(bs, qiov, pos);
+    if (offset < 0) {
+        return offset;
+    }

     BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
-    return bs->drv->bdrv_co_pwritev_part(bs, qcow2_vm_state_offset(s) + pos,
-                                         qiov->size, qiov, 0, 0);
+    return bs->drv->bdrv_co_pwritev_part(bs, offset, qiov->size, qiov, 0, 0);
 }

 static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
                               int64_t pos)
 {
-    BDRVQcow2State *s = bs->opaque;
+    int64_t offset = qcow2_check_vmstate_request(bs, qiov, pos);
+    if (offset < 0) {
+        return offset;
+    }

     BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
-    return bs->drv->bdrv_co_preadv_part(bs, qcow2_vm_state_offset(s) + pos,
-                                        qiov->size, qiov, 0, 0);
+    return bs->drv->bdrv_co_preadv_part(bs, offset, qiov->size, qiov, 0, 0);
 }

 /*
-- 
2.31.1