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: Wed, 4 Mar 2020 16:21:41 +0100 [thread overview]
Message-ID: <db0355a2-c00e-b84e-64d7-55a6dc7d0859@suse.com> (raw)
In-Reply-To: <d6c474e3-f2a5-5f7c-01e8-cb6ad7533ebd@suse.com>
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:
>>>>> On 03.03.20 17:59, Jan Beulich wrote:
>>>>>> On 26.02.2020 13:46, Juergen Gross wrote:
>>>>>>> --- /dev/null
>>>>>>> +++ b/xen/common/hypfs.c
>>>>>>> @@ -0,0 +1,349 @@
>>>>>>> +/******************************************************************************
>>>>>>> + *
>>>>>>> + * hypfs.c
>>>>>>> + *
>>>>>>> + * Simple sysfs-like file system for the hypervisor.
>>>>>>> + */
>>>>>>> +
>>>>>>> +#include <xen/err.h>
>>>>>>> +#include <xen/guest_access.h>
>>>>>>> +#include <xen/hypercall.h>
>>>>>>> +#include <xen/hypfs.h>
>>>>>>> +#include <xen/lib.h>
>>>>>>> +#include <xen/rwlock.h>
>>>>>>> +#include <public/hypfs.h>
>>>>>>> +
>>>>>>> +#ifdef CONFIG_COMPAT
>>>>>>> +#include <compat/hypfs.h>
>>>>>>> +CHECK_hypfs_direntry;
>>>>>>> +#undef CHECK_hypfs_direntry
>>>>>>> +#define CHECK_hypfs_direntry struct xen_hypfs_direntry
>>>>>>
>>>>>> I'm struggling to see why you need this #undef and #define.
>>>>>
>>>>> Without those I get:
>>>>>
>>>>> In file included from /home/gross/xen/unstable/xen/include/compat/xen.h:3:0,
>>>>> from /home/gross/xen/unstable/xen/include/xen/shared.h:6,
>>>>> from /home/gross/xen/unstable/xen/include/xen/sched.h:8,
>>>>> from /home/gross/xen/unstable/xen/include/asm/paging.h:29,
>>>>> from
>>>>> /home/gross/xen/unstable/xen/include/asm/guest_access.h:1,
>>>>> from
>>>>> /home/gross/xen/unstable/xen/include/xen/guest_access.h:1,
>>>>> from hypfs.c:9:
>>>>> /home/gross/xen/unstable/xen/include/xen/compat.h:134:32: error:
>>>>> redefinition of ‘__checkFstruct_hypfs_direntry__flags’
>>>>> #define CHECK_NAME_(k, n, tag) __check ## tag ## k ## _ ## n
>>>>> ^
>>>>> /home/gross/xen/unstable/xen/include/xen/compat.h:166:34: note: in
>>>>> definition of macro ‘CHECK_FIELD_COMMON_’
>>>>> static inline int __maybe_unused name(k xen_ ## n *x, k compat_ ## n *c) \
>>>>> ^~~~
>>>>> /home/gross/xen/unstable/xen/include/xen/compat.h:176:28: note: in
>>>>> expansion of macro ‘CHECK_NAME_’
>>>>> CHECK_FIELD_COMMON_(k, CHECK_NAME_(k, n ## __ ## f, F), n, f)
>>>>> ^~~~~~~~~~~
>>>>> /home/gross/xen/unstable/xen/include/compat/xlat.h:775:5: note: in
>>>>> expansion of macro ‘CHECK_FIELD_’
>>>>> CHECK_FIELD_(struct, hypfs_direntry, flags); \
>>>>> ^~~~~~~~~~~~
>>>>> /home/gross/xen/unstable/xen/include/compat/xlat.h:782:5: note: in
>>>>> expansion of macro ‘CHECK_hypfs_direntry’
>>>>> CHECK_hypfs_direntry; \
>>>>> ^~~~~~~~~~~~~~~~~~~~
>>>>> hypfs.c:19:1: note: in expansion of macro ‘CHECK_hypfs_dirlistentry’
>>>>> CHECK_hypfs_dirlistentry;
>>>>> ^~~~~~~~~~~~~~~~~~~~~~~~
>>>>> /home/gross/xen/unstable/xen/include/xen/compat.h:134:32: note: previous
>>>>> definition of ‘__checkFstruct_hypfs_direntry__flags’ was here
>>>>> #define CHECK_NAME_(k, n, tag) __check ## tag ## k ## _ ## n
>>>>> ^
>>>>> /home/gross/xen/unstable/xen/include/xen/compat.h:166:34: note: in
>>>>> definition of macro ‘CHECK_FIELD_COMMON_’
>>>>> static inline int __maybe_unused name(k xen_ ## n *x, k compat_ ## n *c) \
>>>>> ^~~~
>>>>> /home/gross/xen/unstable/xen/include/xen/compat.h:176:28: note: in
>>>>> expansion of macro ‘CHECK_NAME_’
>>>>> CHECK_FIELD_COMMON_(k, CHECK_NAME_(k, n ## __ ## f, F), n, f)
>>>>> ^~~~~~~~~~~
>>>>> /home/gross/xen/unstable/xen/include/compat/xlat.h:775:5: note: in
>>>>> expansion of macro ‘CHECK_FIELD_’
>>>>> CHECK_FIELD_(struct, hypfs_direntry, flags); \
>>>>> ^~~~~~~~~~~~
>>>>> hypfs.c:18:1: note: in expansion of macro ‘CHECK_hypfs_direntry’
>>>>> CHECK_hypfs_direntry;
>>>>
>>>> Which suggests to me that the explicit CHECK_hypfs_direntry invocation
>>>> is unneeded, as it's getting verified as part of the invocation of
>>>> CHECK_hypfs_dirlistentry.
>>>
>>> Ah, right. This is working. Will change.
>>>
>>>>
>>>>>>> +int hypfs_write_leaf(struct hypfs_entry_leaf *leaf,
>>>>>>> + XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
>>>>>>> +{
>>>>>>> + char *buf;
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + if ( ulen > leaf->e.size )
>>>>>>> + return -ENOSPC;
>>>>>>> +
>>>>>>> + if ( leaf->e.type != XEN_HYPFS_TYPE_STRING &&
>>>>>>> + leaf->e.type != XEN_HYPFS_TYPE_BLOB && ulen != leaf->e.size )
>>>>>>> + return -EDOM;
>>>>>>
>>>>>> Why the exception of string and blob? My concern about the
>>>>>> meaning of a partially written entry (without its size having
>>>>>> changed) remains.
>>>>>
>>>>> 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.
Jan
>> even worse for BLOB-type entries, where one couldn't even look
>> for a nul terminator to determine actual payload size.
>
> Right, this would probably require a blob-specific read function, in
> case the blob is of variable length.
>
>
> Juergen
>
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next prev parent reply other threads:[~2020-03-04 15:21 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 [this message]
2020-03-06 6:06 ` Jürgen Groß
2020-03-06 8:19 ` Jan Beulich
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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