Re: [PATCH] ucounts: add missing data type changes

From: Sven Schnelle
Date: Wed Jul 21 2021 - 08:34:19 EST


Alexey Gladkov <legion@xxxxxxxxxx> 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@xxxxxxxxxxxxx>
>> ---
>> 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
>>