From: Shreeya Patel <shreeya.patel@collabora.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: tytso@mit.edu, adilger.kernel@dilger.ca, jaegeuk@kernel.org,
chao@kernel.org, krisman@collabora.com, drosen@google.com,
yuchao0@huawei.com, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-fsdevel@vger.kernel.org, kernel@collabora.com,
andre.almeida@collabora.com
Subject: Re: [PATCH v4 5/5] fs: unicode: Add utf8 module and a unicode layer
Date: Fri, 26 Mar 2021 02:56:01 +0530 [thread overview]
Message-ID: <cb4e2292-51dc-70af-1b5f-b8312f94d82f@collabora.com> (raw)
In-Reply-To: <2db48ab8-1297-e044-dcec-6c8b8875fdb0@collabora.com>
On 26/03/21 1:56 am, Shreeya Patel wrote:
>
> On 26/03/21 1:10 am, Eric Biggers wrote:
>> On Thu, Mar 25, 2021 at 05:38:11AM +0530, Shreeya Patel wrote:
>>> Also, indirect calls using function pointers are easily exploitable by
>>> speculative execution attacks, hence use static_call() in unicode.h and
>>> unicode-core.c files inorder to prevent these attacks by making direct
>>> calls and also to improve the performance of function pointers.
>> I don't think you need to worry about avoiding indirect calls to prevent
>> speculative execution attacks. That's what the mitigations like
>> Retpoline are
>> for. Instead my concern was just that indirect calls are *slow*,
>> especially
>> when those mitigations are enabled. Some of the casefolding
>> operations are
>> called a lot (e.g., repeatedly during path resolution), and it would be
>> desirable to avoid adding more overhead there.
>>
>>> diff --git a/fs/unicode/Kconfig b/fs/unicode/Kconfig
>>> index 2c27b9a5cd6c..2961b0206b4d 100644
>>> --- a/fs/unicode/Kconfig
>>> +++ b/fs/unicode/Kconfig
>>> @@ -8,7 +8,16 @@ config UNICODE
>>> Say Y here to enable UTF-8 NFD normalization and NFD+CF
>>> casefolding
>>> support.
>>> +# UTF-8 encoding can be compiled as a module using UNICODE_UTF8
>>> option.
>>> +# Having UTF-8 encoding as a module will avoid carrying large
>>> +# database table present in utf8data.h_shipped into the kernel
>>> +# by being able to load it only when it is required by the filesystem.
>>> +config UNICODE_UTF8
>>> + tristate "UTF-8 module"
>>> + depends on UNICODE
>>> + default m
>>> +
>> The help for UNICODE still says that it enables UTF-8 support. But
>> now there is
>> a separate option that people will need to remember to enable.
>>
>> Please document each of these options properly.
>>
>> Perhaps EXT4_FS and F2FS_FS just should select UNICODE_UTF8 if
>> UNICODE, so that
>> UNICODE_UTF8 doesn't have to be a user-selectable symbol?
>
>
> It is not a user-selectable symbol. It depends on UNICODE and if
> someone enables it,
> by default UNICODE_UTF8 will be enabled as a module.
>
>
Sorry, I think I misunderstood when you said EXT4_FS and F2FS_FS should
select
UNICODE_UTF8 if UNICODE is enabled. I now get it that you don't want
them to be deselectable.
I'll make this change. Thanks
>>> +DEFINE_STATIC_CALL(validate, unicode_validate_static_call);
>>> +EXPORT_STATIC_CALL(validate);
>> Global symbols can't have generic names like "validate". Please add an
>> appropriate prefix like "unicode_".
>>
>> Also, the thing called "unicode_validate_static_call" isn't actually
>> a static
>> call as the name suggests, but rather the default function used by
>> the static
>> call. It should be called something like unicode_validate_default.
>>
>> Likewise for all the others.
>
>
> Thanks for your reviews, I'll make the change suggested by you in v5.
>
>
>>
>> - Eric
>>
prev parent reply other threads:[~2021-03-25 21:27 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 0:08 [PATCH v4 0/5] Make UTF-8 encoding loadable Shreeya Patel
2021-03-25 0:08 ` [PATCH v4 1/5] fs: unicode: Use strscpy() instead of strncpy() Shreeya Patel
2021-03-25 0:08 ` [PATCH v4 2/5] fs: Check if utf8 encoding is loaded before calling utf8_unload() Shreeya Patel
2021-03-25 19:21 ` Eric Biggers
2021-03-25 19:31 ` Gabriel Krisman Bertazi
2021-03-25 19:43 ` Eric Biggers
2021-03-25 0:08 ` [PATCH v4 3/5] fs: unicode: Rename function names from utf8 to unicode Shreeya Patel
2021-03-25 19:24 ` Eric Biggers
2021-03-25 0:08 ` [PATCH v4 4/5] fs: unicode: Rename utf8-core file to unicode-core Shreeya Patel
2021-03-25 0:08 ` [PATCH v4 5/5] fs: unicode: Add utf8 module and a unicode layer Shreeya Patel
2021-03-25 19:40 ` Eric Biggers
2021-03-25 20:26 ` Shreeya Patel
2021-03-25 21:26 ` Shreeya Patel [this message]
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