From: Jan Beulich <jbeulich@suse.com>
To: "Jürgen Groß" <jgross@suse.com>
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
"Julien Grall" <julien@xen.org>, "Wei Liu" <wl@xen.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
xen-devel@lists.xenproject.org,
"Daniel De Graaf" <dgdegra@tycho.nsa.gov>,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v6 04/12] xen: add basic hypervisor filesystem support
Date: Fri, 6 Mar 2020 09:19:09 +0100 [thread overview]
Message-ID: <db9f4d33-8059-4e27-c44a-cef59d0a5144@suse.com> (raw)
In-Reply-To: <c799989e-fc68-15f9-4d1f-3e1d8d452fcc@suse.com>
On 06.03.2020 07:06, Jürgen Groß wrote:
> On 04.03.20 16:21, Jan Beulich wrote:
>> On 04.03.2020 16:14, Jürgen Groß wrote:
>>> On 04.03.20 16:07, Jan Beulich wrote:
>>>> On 04.03.2020 15:39, Jürgen Groß wrote:
>>>>> On 04.03.20 14:03, Jan Beulich wrote:
>>>>>> On 04.03.2020 13:00, Jürgen Groß wrote:
>>>>>>> It is perfectly valid to write a shorter string into a character
>>>>>>> array. I could drop the blob here, but in the end I think allowing
>>>>>>> for a blob to change the size should be fine.
>>>>>>
>>>>>> But shouldn't this then also adjust the recorded size?
>>>>>
>>>>> No, this is the max size of the buffer (you can have a look at patch 9
>>>>> where the size is set to the provided space for custom and string
>>>>> parameters).
>>>>
>>>> If I'm not mistaken it is hypfs_read_leaf() which processes read
>>>> requests for strings. Yet that copies entry->size bytes, not the
>>>> potentially smaller strlen()-bounded payload. Things would be
>>>
>>> There is no risk of leaking problematic data here.
>>
>> I didn't think of leaks, but rather of consumers looking at the
>> size and strlen() and getting confused about the mismatch.
>
> I think telling the maximum possible write length is mandatory.
>
> So either I can add a comment to the header saying that for strings
> and blobs the length is the maximum value and the content is to be
> self-descriptive regarding its true length (which is the case for
> strings due to the terminating 0 byte), or I need two size fields:
> one for the actual size and one for the maximum allowed size for
> writes (this could then replace the writable flag with "0" for "not
> writable").
Personally I'd prefer the latter, but I could also live with a
comment. The self-descriptive part may, for blobs or gzip-ed
data, be problematic though.
Jan
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next prev parent reply other threads:[~2020-03-06 8:19 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 12:46 [Xen-devel] [PATCH v6 00/12] Add hypervisor sysfs-like support Juergen Gross
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 01/12] xen: allow only sizeof(bool) variables for boolean_param() Juergen Gross
2020-03-03 16:40 ` Jan Beulich
2020-03-09 11:43 ` Julien Grall
2020-03-09 11:55 ` Jan Beulich
2020-03-09 13:01 ` Jürgen Groß
2020-03-09 13:06 ` Jan Beulich
2020-03-09 14:06 ` Jürgen Groß
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 02/12] xen: add a generic way to include binary files as variables Juergen Gross
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 03/12] docs: add feature document for Xen hypervisor sysfs-like support Juergen Gross
2020-03-09 11:48 ` Julien Grall
2020-03-25 14:05 ` Jürgen Groß
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 04/12] xen: add basic hypervisor filesystem support Juergen Gross
2020-03-03 16:59 ` Jan Beulich
2020-03-04 12:00 ` Jürgen Groß
2020-03-04 13:03 ` Jan Beulich
2020-03-04 14:39 ` Jürgen Groß
2020-03-04 15:07 ` Jan Beulich
2020-03-04 15:14 ` Jürgen Groß
2020-03-04 15:21 ` Jan Beulich
2020-03-06 6:06 ` Jürgen Groß
2020-03-06 8:19 ` Jan Beulich [this message]
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 05/12] libs: add libxenhypfs Juergen Gross
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 06/12] tools: add xenfs tool Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 07/12] xen: provide version information in hypfs Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 08/12] xen: add /buildinfo/config entry to hypervisor filesystem Juergen Gross
2020-03-04 10:49 ` Jan Beulich
2020-03-04 12:06 ` Jürgen Groß
2020-03-04 13:04 ` Jan Beulich
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 09/12] xen: add runtime parameter access support to hypfs Juergen Gross
2020-03-04 11:32 ` Jan Beulich
2020-03-04 15:07 ` Jürgen Groß
2020-03-04 15:19 ` Jan Beulich
2020-03-04 16:31 ` Jürgen Groß
2020-03-04 16:56 ` Jan Beulich
2020-03-05 6:01 ` Jürgen Groß
2020-03-05 8:26 ` Jan Beulich
2020-03-06 6:42 ` Jürgen Groß
2020-03-06 8:20 ` Jan Beulich
2020-03-06 8:47 ` Jürgen Groß
2020-03-06 9:04 ` Jan Beulich
2020-03-06 9:20 ` Jürgen Groß
2020-03-06 9:22 ` Jan Beulich
2020-03-06 9:27 ` Jürgen Groß
2020-03-23 10:38 ` Julien Grall
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 10/12] tools/libxl: use libxenhypfs for setting xen runtime parameters Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 11/12] tools/libxc: remove xc_set_parameters() Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 12/12] xen: remove XEN_SYSCTL_set_parameter support Juergen Gross
2020-03-04 11:45 ` Jan Beulich
2020-03-04 14:40 ` Jürgen Groß
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