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Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'n
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From: |
Philippe Mathieu-Daudé |
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Subject: |
Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver |
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Date: |
Fri, 12 Feb 2021 15:32:47 +0100 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 |
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)
- [PATCH v2 1/2] block: Explicit null-co uses 'read-zeroes=false', (continued)
- [PATCH v2 1/2] block: Explicit null-co uses 'read-zeroes=false', Philippe Mathieu-Daudé, 2021/02/11
- [PATCH v2 2/2] block/null: Enable 'read-zeroes' mode by default, Philippe Mathieu-Daudé, 2021/02/11
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Alexander Bulekov, 2021/02/11
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver,
Philippe Mathieu-Daudé <=
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Fam Zheng, 2021/02/13
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Max Reitz, 2021/02/19
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Philippe Mathieu-Daudé, 2021/02/19
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Fam Zheng, 2021/02/22
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Philippe Mathieu-Daudé, 2021/02/22
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Fam Zheng, 2021/02/23
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Max Reitz, 2021/02/23
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Fam Zheng, 2021/02/23
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Daniel P . Berrangé, 2021/02/22
- Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver, Philippe Mathieu-Daudé, 2021/02/22