From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: Alexander Bulekov <alxndr@bu.edu>
Cc: Fam Zheng <fam@euphon.net>, Laurent Vivier <lvivier@redhat.com>,
Thomas Huth <thuth@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
Wainer dos Santos Moschetta <wainersm@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
Kevin Wolf <kwolf@redhat.com>, Bandan Das <bsd@redhat.com>,
Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Cleber Rosa <crosa@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Max Reitz <mreitz@redhat.com>
Subject: Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver
Date: Fri, 12 Feb 2021 15:32:47 +0100 [thread overview]
Message-ID: <2792857c-403a-c3f0-9635-e3b973347dd9@redhat.com> (raw)
In-Reply-To: <20210211154228.izwdqb33dxtnu65n@mozz.bu.edu>
On 2/11/21 4:42 PM, Alexander Bulekov wrote:
> On 210211 1526, Philippe Mathieu-Daudé wrote:
>> The null-co driver doesn't zeroize buffer in its default config,
>> because it is designed for testing and tests want to run fast.
>> However this confuses security researchers (access to uninit
>> buffers).
>>
>
> Interesting.. Is there an example bug report, where it raised alarms
> because of an un-zeroed null-co:// buffer?
No, but I found a similar mention here:
https://www.mail-archive.com/qemu-block@nongnu.org/msg52045.html
Example:
$ valgrind qemu-system-i386 -S -drive
file=null-co://,format=raw,file.read-zeroes=on
$ valgrind qemu-system-i386 -S -drive
file=null-co://,format=raw,file.read-zeroes=off
==4048219== Conditional jump or move depends on uninitialised value(s)
==4048219== at 0x4E19CC: guess_disk_lchs (hd-geometry.c:70)
==4048219== by 0x4E1C72: hd_geometry_guess (hd-geometry.c:131)
==4048219== by 0x4E0F0F: blkconf_geometry (block.c:183)
==4048219== by 0x563727: ide_dev_initfn (qdev.c:201)
==4048219== by 0x563AE4: ide_hd_realize (qdev.c:278)
==4048219== by 0x563320: ide_qdev_realize (qdev.c:124)
==4048219== by 0x8F8EAA: device_set_realized (qdev.c:761)
==4048219== by 0x902347: property_set_bool (object.c:2255)
==4048219== by 0x900441: object_property_set (object.c:1400)
==4048219== by 0x904467: object_property_set_qobject (qom-qobject.c:28)
==4048219== by 0x9007A4: object_property_set_bool (object.c:1470)
==4048219== by 0x8F7F3B: qdev_realize (qdev.c:389)
next prev parent reply other threads:[~2021-02-12 14:33 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 14:26 [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver Philippe Mathieu-Daudé
2021-02-11 14:26 ` [PATCH v2 1/2] block: Explicit null-co uses 'read-zeroes=false' Philippe Mathieu-Daudé
2021-02-11 16:29 ` Vladimir Sementsov-Ogievskiy
2021-02-11 19:19 ` Philippe Mathieu-Daudé
2021-02-11 22:40 ` Eric Blake
2021-02-11 23:49 ` Philippe Mathieu-Daudé
2021-02-12 11:34 ` Vladimir Sementsov-Ogievskiy
2021-02-12 19:06 ` Eric Blake
2021-02-11 14:26 ` [PATCH v2 2/2] block/null: Enable 'read-zeroes' mode by default Philippe Mathieu-Daudé
2021-02-11 16:22 ` Stefan Hajnoczi
2021-02-11 15:42 ` [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver Alexander Bulekov
2021-02-12 14:32 ` Philippe Mathieu-Daudé [this message]
2021-02-13 21:54 ` Fam Zheng
2021-02-19 11:07 ` Max Reitz
2021-02-19 14:09 ` Philippe Mathieu-Daudé
2021-02-22 17:35 ` Fam Zheng
2021-02-22 17:55 ` Philippe Mathieu-Daudé
2021-02-23 9:21 ` Fam Zheng
2021-02-23 16:01 ` Max Reitz
2021-02-23 17:21 ` Fam Zheng
2021-02-22 18:15 ` Daniel P. Berrangé
2021-02-22 18:36 ` Philippe Mathieu-Daudé
2021-02-23 8:44 ` Max Reitz
2021-02-23 9:29 ` Daniel P. Berrangé
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