Blob Blame Raw
From a32c9e8da011b25ba9a056bc41c990694b730566 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Wed, 13 Dec 2017 13:38:51 +0100
Subject: [PATCH 20/41] dump: Fix dump-guest-memory termination and
 use-after-close
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

RH-Author: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: <20171213133912.26176-21-marcandre.lureau@redhat.com>
Patchwork-id: 78374
O-Subject: [RHEL-7.5 qemu-kvm PATCH v3 20/41] dump: Fix dump-guest-memory termination and use-after-close
Bugzilla: 1411490
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: Gonglei <arei.gonglei@huawei.com>

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>

(cherry picked from commit 08a655be71d0a130a5d9bf7816d096ec31c4f055)
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 dump.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/dump.c b/dump.c
index 099346a..83b6d20 100644
--- a/dump.c
+++ b/dump.c
@@ -610,10 +610,9 @@ 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;
@@ -629,11 +628,9 @@ 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)
-- 
1.8.3.1