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vmdk: Use g_random_int to generate CID

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This replaces two "time(NULL)" invocations with "g_random_int()".
According to VMDK spec, CID "is a random 32‐bit value updated the first
time the content of the virtual disk is modified after the virtual disk
is opened". Using "seconds since epoch" is just a "lame way" to generate
it, and not completely safe because of the low precision.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Don Koch <dkoch@verizon.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 1417649314-13704-2-git-send-email-famz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Fam Zheng 2014-12-04 07:28:29 +08:00 committed by Kevin Wolf
parent 3ba235a022
commit e5dc64b8ff
1 changed files with 3 additions and 2 deletions
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5
block/vmdk.c
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@ -28,6 +28,7 @@
#include "qemu/module.h"
#include "migration/migration.h"
#include <zlib.h>
#include <glib.h>
#define VMDK3_MAGIC (('C' << 24) | ('O' << 16) | ('W' << 8) | 'D')
#define VMDK4_MAGIC (('K' << 24) | ('D' << 16) | ('M' << 8) | 'V')
@ -1538,7 +1539,7 @@ static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
/* update CID on the first write every time the virtual disk is
* opened */
if (!s->cid_updated) {
ret = vmdk_write_cid(bs, time(NULL));
ret = vmdk_write_cid(bs, g_random_int());
if (ret < 0) {
return ret;
}
@ -1922,7 +1923,7 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
}
/* generate descriptor file */
desc = g_strdup_printf(desc_template,
(uint32_t)time(NULL),
g_random_int(),
parent_cid,
fmt,
parent_desc_line,