[Qemu-devel] [PULL 2.7 2/4] migration: mmap error check fix

[Amit Shah <amit.shah@redhat.com>]

From: Evgeny Yakovlev <eyakovlev@virtuozzo.com>

mmap man page:
"On success, mmap() returns a pointer to the mapped area. On error, the
value MAP_FAILED (that is, (void *) -1) is returned, and errno  is  set
to indicate the cause of the error."

The check in postcopy_get_tmp_page is definitely wrong and should be
fixed.

Signed-off-by: Evgeny Yakovlev <eyakovlev@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Amit Shah <amit.shah@redhat.com>
Message-Id: <1469785705-16670-1-git-send-email-den@openvz.org>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 migration/postcopy-ram.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index abe8c60..9b04778 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -604,7 +604,8 @@ void *postcopy_get_tmp_page(MigrationIncomingState *mis)
         mis->postcopy_tmp_page = mmap(NULL, getpagesize(),
                              PROT_READ | PROT_WRITE, MAP_PRIVATE |
                              MAP_ANONYMOUS, -1, 0);
-        if (!mis->postcopy_tmp_page) {
+        if (mis->postcopy_tmp_page == MAP_FAILED) {
+            mis->postcopy_tmp_page = NULL;
             error_report("%s: %s", __func__, strerror(errno));
             return NULL;
         }
-- 
2.7.4