linux-kernel - Re: [PATCH] iouring:added boundary value check for io_uring

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Message-ID: <37ed354a-6b69-4e24-9557-5ca62179b76a@gmail.com>
Date: Sat, 20 Jan 2024 19:39:22 +0530
From: Subramanya Swamy <subramanya.swamy.linux@...il.com>
To: Jeff Moyer <jmoyer@...hat.com>
Cc: corbet@....net, axboe@...nel.dk, asml.silence@...il.com,
 ribalda@...omium.org, rostedt@...dmis.org, bhe@...hat.com,
 akpm@...ux-foundation.org, matteorizzo@...gle.com, ardb@...nel.org,
 alexghiti@...osinc.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, io-uring@...r.kernel.org
Subject: Re: [PATCH] iouring:added boundary value check for io_uring_group
 systl

Hi Jeff,

            Thank you for reviewing the patch.

On 16/01/24 23:16, Jeff Moyer wrote:
> Subramanya Swamy <subramanya.swamy.linux@...il.com> writes:
>
>> /proc/sys/kernel/io_uring_group takes gid as input
>> added boundary value check to accept gid in range of
>> 0<=gid<=4294967294 & Documentation is updated for same
> Thanks for the patch.  You're right, the current code artificially
> limits the maximum group id.
>
>> Signed-off-by: Subramanya Swamy <subramanya.swamy.linux@...il.com>
>> ---
>>   Documentation/admin-guide/sysctl/kernel.rst | 9 ++++-----
>>   io_uring/io_uring.c                         | 8 ++++++--
>>   2 files changed, 10 insertions(+), 7 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
>> index 6584a1f9bfe3..3f96007aa971 100644
>> --- a/Documentation/admin-guide/sysctl/kernel.rst
>> +++ b/Documentation/admin-guide/sysctl/kernel.rst
>> @@ -469,11 +469,10 @@ shrinks the kernel's attack surface.
>>   io_uring_group
>>   ==============
>>   
>> -When io_uring_disabled is set to 1, a process must either be
>> -privileged (CAP_SYS_ADMIN) or be in the io_uring_group group in order
>> -to create an io_uring instance.  If io_uring_group is set to -1 (the
>> -default), only processes with the CAP_SYS_ADMIN capability may create
>> -io_uring instances.
>> +When io_uring_disabled is set to 1, only processes with the
>> +CAP_SYS_ADMIN may create io_uring instances or process must be in the
>> +io_uring_group group in order to create an io_uring_instance.
>> +io_uring_group is set to 0.This is the default setting.
> You are changing the default from an invalid group to the root group.  I
> guess that's ok, but I'd rather keep it the way it is.  The text is a
> bit repetitive.  Why not just this?
>
> "When io_uring_disabled is set to 1, a process must either be
>   privileged (CAP_SYS_ADMIN) or be in the io_uring_group group in order
>   to create an io_uring instance."

Yes this looks neat , will add in v2

>> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
>> index 09b6d860deba..0ed91b69643d 100644
>> --- a/io_uring/io_uring.c
>> +++ b/io_uring/io_uring.c
>> @@ -146,7 +146,9 @@ static void io_queue_sqe(struct io_kiocb *req);
>>   struct kmem_cache *req_cachep;
>>   
>>   static int __read_mostly sysctl_io_uring_disabled;
>> -static int __read_mostly sysctl_io_uring_group = -1;
>> +static unsigned int __read_mostly sysctl_io_uring_group;
>> +static unsigned int min_gid;
>> +static unsigned int max_gid  = 4294967294;  /*4294967294 is the max guid*/
> Right, INVALID_GID is -1.
>
>>   #ifdef CONFIG_SYSCTL
>>   static struct ctl_table kernel_io_uring_disabled_table[] = {
>> @@ -164,7 +166,9 @@ static struct ctl_table kernel_io_uring_disabled_table[] = {
>>   		.data		= &sysctl_io_uring_group,
>>   		.maxlen		= sizeof(gid_t),
>>   		.mode		= 0644,
>> -		.proc_handler	= proc_dointvec,
>> +		.proc_handler	= proc_douintvec_minmax,
>> +		.extra1         = &min_gid,
> This should be SYSCTL_ZERO.

will change this to SYSCTL_ZERO in v2

>> +		.extra2         = &max_gid,
>>   	},
>>   	{},
>>   };
> Thanks!
> Jeff
>
-- 
Best Regards
Subramanya