linux-kernel - Re: [PATCH] ucounts: add missing data type changes

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Message-ID: <yt9dtuknaluh.fsf@linux.ibm.com>
Date:   Wed, 21 Jul 2021 14:32:38 +0200
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     Alexey Gladkov <legion@...nel.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ucounts: add missing data type changes

Alexey Gladkov <legion@...nel.org> writes:

> On Wed, Jul 21, 2021 at 01:58:00PM +0200, Sven Schnelle wrote:
>> commit f9c82a4ea89c3 ("Increase size of ucounts to atomic_long_t")
>> changed the data type of ucounts/ucounts_max to long, but missed to
>> adjust a few other places. This is noticeable on big endian platforms
>> from user space because the /proc/sys/user/max_*_names files all
>> contain 0.
>
> I didn't increase them because I didn't want to increase the maximum
> number of namespaces.
>
> Your patch not only fixes the described problem, but also increases the
> maximum number of namespaces.
>
>> Fixes: f9c82a4ea89c ("Increase size of ucounts to atomic_long_t")
>> Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
>> ---
>>  fs/notify/fanotify/fanotify_user.c | 11 +++++++----
>>  kernel/ucount.c                    | 18 ++++++++++--------
>>  kernel/user_namespace.c            |  2 +-
>>  3 files changed, 18 insertions(+), 13 deletions(-)
>> 
>> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
>> index 64864fb40b40..995379ddce86 100644
>> --- a/fs/notify/fanotify/fanotify_user.c
>> +++ b/fs/notify/fanotify/fanotify_user.c
>> @@ -54,22 +54,25 @@ static int fanotify_max_queued_events __read_mostly;
>>  
>>  #include <linux/sysctl.h>
>>  
>> +static unsigned long long_max = LONG_MAX;
>
> I think this should be INT_MAX.

Thanks. I'll change the code to use SYSCTL_INT_MAX instead and send a
v2.

>>  struct ctl_table fanotify_table[] = {
>>  	{
>>  		.procname	= "max_user_groups",
>>  		.data	= &init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS],
>> -		.maxlen		= sizeof(int),
>> +		.maxlen		= sizeof(long),
>>  		.mode		= 0644,
>> -		.proc_handler	= proc_dointvec_minmax,
>> +		.proc_handler	= proc_doulongvec_minmax,
>>  		.extra1		= SYSCTL_ZERO,
>> +		.extra2		= &long_max,
>>  	},
>>  	{
>>  		.procname	= "max_user_marks",
>>  		.data	= &init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS],
>> -		.maxlen		= sizeof(int),
>> +		.maxlen		= sizeof(long),
>>  		.mode		= 0644,
>> -		.proc_handler	= proc_dointvec_minmax,
>> +		.proc_handler	= proc_doulongvec_minmax,
>>  		.extra1		= SYSCTL_ZERO,
>> +		.extra2		= &long_max,
>>  	},
>>  	{
>>  		.procname	= "max_queued_events",
>> diff --git a/kernel/ucount.c b/kernel/ucount.c
>> index 87799e2379bd..681ea1b1a06f 100644
>> --- a/kernel/ucount.c
>> +++ b/kernel/ucount.c
>> @@ -58,14 +58,16 @@ static struct ctl_table_root set_root = {
>>  	.permissions = set_permissions,
>>  };
>>  
>> -#define UCOUNT_ENTRY(name)				\
>> -	{						\
>> -		.procname	= name,			\
>> -		.maxlen		= sizeof(int),		\
>> -		.mode		= 0644,			\
>> -		.proc_handler	= proc_dointvec_minmax,	\
>> -		.extra1		= SYSCTL_ZERO,		\
>> -		.extra2		= SYSCTL_INT_MAX,	\
>> +static unsigned long long_max = LONG_MAX;
>> +
>> +#define UCOUNT_ENTRY(name)					\
>> +	{							\
>> +		.procname	= name,				\
>> +		.maxlen		= sizeof(long),			\
>> +		.mode		= 0644,				\
>> +		.proc_handler	= proc_doulongvec_minmax,	\
>> +		.extra1		= SYSCTL_ZERO,			\
>> +		.extra2		= &long_max,			\
>>  	}
>>  static struct ctl_table user_table[] = {
>>  	UCOUNT_ENTRY("max_user_namespaces"),
>> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
>> index ef82d401dde8..d8ad4c261253 100644
>> --- a/kernel/user_namespace.c
>> +++ b/kernel/user_namespace.c
>> @@ -120,7 +120,7 @@ int create_user_ns(struct cred *new)
>>  	ns->group = group;
>>  	INIT_WORK(&ns->work, free_user_ns);
>>  	for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) {
>> -		ns->ucount_max[i] = INT_MAX;
>> +		ns->ucount_max[i] = LONG_MAX;

Guess this should also stay at INT_MAX?

>>  	}
>>  	set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC));
>>  	set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
>> -- 
>> 2.25.1
>>