dump: Fix dump-guest-memory termination and use-after-close

dump_iterate() dumps blocks in a loop.  Eventually, get_next_block()
returns "no more".  We then call dump_completed().  But we neglect to
break the loop!  Broken in commit 4c7e251a.

Because of that, we dump the last block again.  This attempts to write
to s->fd, which fails if we're lucky.  The error makes dump_iterate()
return failure.  It's the only way it can ever return.

Theoretical: if we're not so lucky, something else has opened something
for writing and got the same fd.  dump_iterate() then keeps looping,
messing up the something else's output, until a write fails, or the
process mercifully terminates.

The obvious fix is to restore the return lost in commit 4c7e251a.  But
the root cause of the bug is needlessly opaque loop control.  Replace it
by a clean do ... while loop.

This makes the badly chosen return values of get_next_block() more
visible.  Cleaning that up is outside the scope of this bug fix.

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/dump.c b/dump.c
index 06a49155a2d4a593784edd2bce86ed72f8d16261..9c7dad8f865af3b778589dd0847e450ba9a75b9d 100644 (file)
--- a/dump.c
+++ b/dump.c
@@ -604,10 +604,9 @@ static void dump_iterate(DumpState *s, Error **errp)
 {
     GuestPhysBlock *block;
     int64_t size;
-    int ret;
     Error *local_err = NULL;
 
-    while (1) {
+    do {
         block = s->next_block;
 
         size = block->target_end - block->target_start;
@@ -623,11 +622,9 @@ static void dump_iterate(DumpState *s, Error **errp)
             return;
         }
 
-        ret = get_next_block(s, block);
-        if (ret == 1) {
-            dump_completed(s);
-        }
-    }
+    } while (!get_next_block(s, block));
+
+    dump_completed(s);
 }
 
 static void create_vmcore(DumpState *s, Error **errp)