[Qemu-devel] [PATCHv4] migration: catch unknown flags in ram_load

[Peter Lieven]

if a saved vm has unknown flags in the memory data qemu
currently simply ignores this flag and continues which
yields in an unpredictable result.

This patch catches all unknown flags and aborts the
loading of the vm. Additionally error reports are thrown
if the migration aborts abnormally.

Signed-off-by: Peter Lieven <address@hidden>
---
v3->v4: - throw error reports where possible [Amit]
        - removed the rework of the last case it missed
          BLOCK_MIG_FLAG_EOS and threw an error.
v2->v3: - reworked last case in the if statement
        - added an error_report in case of an unknown flag [David]
v1->v2: rework loop from do ... while to while [Juan]
 
 arch_init.c |   42 +++++++++++++++++++++++-------------------
 migration.c |    2 +-
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 9f1a174..4ee782f 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -1041,17 +1041,15 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
 {
     ram_addr_t addr;
     int flags, ret = 0;
-    int error;
     static uint64_t seq_iter;
 
     seq_iter++;
 
     if (version_id != 4) {
         ret = -EINVAL;
-        goto done;
     }
 
-    do {
+    while (!ret) {
         addr = qemu_get_be64(f);
 
         flags = addr & ~TARGET_PAGE_MASK;
@@ -1079,7 +1077,6 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
                                          " in != " RAM_ADDR_FMT, id, length,
                                          block->length);
                             ret =  -EINVAL;
-                            goto done;
                         }
                         break;
                     }
@@ -1089,21 +1086,22 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
                     error_report("Unknown ramblock \"%s\", cannot "
                                  "accept migration", id);
                     ret = -EINVAL;
-                    goto done;
+                }
+                if (ret) {
+                    break;
                 }
 
                 total_ram_bytes -= length;
             }
-        }
-
-        if (flags & RAM_SAVE_FLAG_COMPRESS) {
+        } else if (flags & RAM_SAVE_FLAG_COMPRESS) {
             void *host;
             uint8_t ch;
 
             host = host_from_stream_offset(f, addr, flags);
             if (!host) {
+                error_report("Illegal RAM offset %" PRIx64, addr);
                 ret = -EINVAL;
-                goto done;
+                break;
             }
 
             ch = qemu_get_byte(f);
@@ -1113,33 +1111,39 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
 
             host = host_from_stream_offset(f, addr, flags);
             if (!host) {
+                error_report("Illegal RAM offset %" PRIx64, addr);
                 ret = -EINVAL;
-                goto done;
+                break;
             }
 
             qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
         } else if (flags & RAM_SAVE_FLAG_XBZRLE) {
             void *host = host_from_stream_offset(f, addr, flags);
             if (!host) {
+                error_report("Illegal RAM offset %" PRIx64, addr);
                 ret = -EINVAL;
-                goto done;
+                break;
             }
 
             if (load_xbzrle(f, addr, host) < 0) {
+                error_report("Failed to decompress XBZRLE page at %" PRIx64,
+                             addr);
                 ret = -EINVAL;
-                goto done;
+                break;
             }
         } else if (flags & RAM_SAVE_FLAG_HOOK) {
             ram_control_load_hook(f, flags);
+        } else if (flags & RAM_SAVE_FLAG_EOS) {
+            /* normal exit */
+            break;
+        } else {
+            error_report("Unknown migration flags: %#x", flags);
+            ret = -EINVAL;
+            break;
         }
-        error = qemu_file_get_error(f);
-        if (error) {
-            ret = error;
-            goto done;
-        }
-    } while (!(flags & RAM_SAVE_FLAG_EOS));
+        ret = qemu_file_get_error(f);
+    }
 
-done:
     DPRINTF("Completed load of VM with exit code %d seq iteration "
             "%" PRIu64 "\n", ret, seq_iter);
     return ret;
diff --git a/migration.c b/migration.c
index 3fc03d6..3ebe9fb 100644
--- a/migration.c
+++ b/migration.c
@@ -98,7 +98,7 @@ static void process_incoming_migration_co(void *opaque)
     qemu_fclose(f);
     free_xbzrle_decoded_buf();
     if (ret < 0) {
-        fprintf(stderr, "load of migration failed\n");
+        error_report("load of migration failed: %s", strerror(-ret));
         exit(EXIT_FAILURE);
     }
     qemu_announce_self();
-- 
1.7.9.5