Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Ma, XinjianX]

Hi Alexey,

When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
in kselftest failed with following message. 

If you confirm and fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot lkp@intel.com

```
# selftests: mqueue: mq_perf_tests
#
# Initial system state:
#       Using queue path:                       /mq_perf_tests
#       RLIMIT_MSGQUEUE(soft):                  819200
#       RLIMIT_MSGQUEUE(hard):                  819200
#       Maximum Message Size:                   8192
#       Maximum Queue Size:                     10
#       Nice value:                             0
#
# Adjusted system state for testing:
#       RLIMIT_MSGQUEUE(soft):                  (unlimited)
#       RLIMIT_MSGQUEUE(hard):                  (unlimited)
#       Maximum Message Size:                   16777216
#       Maximum Queue Size:                     65530
#       Nice value:                             -20
#       Continuous mode:                        (disabled)
#       CPUs to pin:                            3
# ./mq_perf_tests: mq_open() at 296: Too many open files
not ok 2 selftests: mqueue: mq_perf_tests # exit=1
```    

Test env:
rootfs: debian-10
gcc version: 9

------
Thanks 
Ma Xinjian

Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Eric W. Biederman]

"Ma, XinjianX" <xinjianx.ma@intel.com> writes:

> Hi Alexey,
>
> When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
> in kselftest failed with following message.

Which kernel was this run against?

Where can the mq_perf_tests that you ran and had problems with be found?

During your run were you using user namespaces as part of your test
environment?

The error message too many files corresponds to the error code EMFILES
which is the error code that is returned when the rlimit is reached.

One possibility is that your test environment was run in a user
namespace and so you wound up limited by rlimit of the user who created
the user namespace at the point of user namespace creation. 

At this point if you can give us enough information to look into this
and attempt to reproduce it that would be appreciated.

> If you confirm and fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot lkp@intel.com
>
> ```
> # selftests: mqueue: mq_perf_tests
> #
> # Initial system state:
> #       Using queue path:                       /mq_perf_tests
> #       RLIMIT_MSGQUEUE(soft):                  819200
> #       RLIMIT_MSGQUEUE(hard):                  819200
> #       Maximum Message Size:                   8192
> #       Maximum Queue Size:                     10
> #       Nice value:                             0
> #
> # Adjusted system state for testing:
> #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> #       Maximum Message Size:                   16777216
> #       Maximum Queue Size:                     65530
> #       Nice value:                             -20
> #       Continuous mode:                        (disabled)
> #       CPUs to pin:                            3
> # ./mq_perf_tests: mq_open() at 296: Too many open files
> not ok 2 selftests: mqueue: mq_perf_tests # exit=1
> ```    
>
> Test env:
> rootfs: debian-10
> gcc version: 9
>
> ------
> Thanks 
> Ma Xinjian

Eric

Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Alexey Gladkov]

On Tue, Aug 17, 2021 at 10:47:14AM -0500, Eric W. Biederman wrote:
> "Ma, XinjianX" <xinjianx.ma@intel.com> writes:
> 
> > Hi Alexey,
> >
> > When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
> > in kselftest failed with following message.
> 
> Which kernel was this run against?
> 
> Where can the mq_perf_tests that you ran and had problems with be found?
> 
> During your run were you using user namespaces as part of your test
> environment?
> 
> The error message too many files corresponds to the error code EMFILES
> which is the error code that is returned when the rlimit is reached.
> 
> One possibility is that your test environment was run in a user
> namespace and so you wound up limited by rlimit of the user who created
> the user namespace at the point of user namespace creation. 
> 
> At this point if you can give us enough information to look into this
> and attempt to reproduce it that would be appreciated.

I was able to reproduce it on master without using user namespace.
I suspect that the maximum value is not assigned here [1]:

set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/fork.c#n832

> > If you confirm and fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot lkp@intel.com
> >
> > ```
> > # selftests: mqueue: mq_perf_tests
> > #
> > # Initial system state:
> > #       Using queue path:                       /mq_perf_tests
> > #       RLIMIT_MSGQUEUE(soft):                  819200
> > #       RLIMIT_MSGQUEUE(hard):                  819200
> > #       Maximum Message Size:                   8192
> > #       Maximum Queue Size:                     10
> > #       Nice value:                             0
> > #
> > # Adjusted system state for testing:
> > #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> > #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> > #       Maximum Message Size:                   16777216
> > #       Maximum Queue Size:                     65530
> > #       Nice value:                             -20
> > #       Continuous mode:                        (disabled)
> > #       CPUs to pin:                            3
> > # ./mq_perf_tests: mq_open() at 296: Too many open files
> > not ok 2 selftests: mqueue: mq_perf_tests # exit=1
> > ```    
> >
> > Test env:
> > rootfs: debian-10
> > gcc version: 9
> >
> > ------
> > Thanks 
> > Ma Xinjian
> 
> Eric
> 

-- 
Rgrds, legion

RE: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Ma, XinjianX]

> -----Original Message-----
> From: Alexey Gladkov <legion@kernel.org>
> Sent: Wednesday, August 18, 2021 9:11 PM
> To: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Ma, XinjianX <xinjianx.ma@intel.com>; linux-kselftest@vger.kernel.org;
> lkp <lkp@intel.com>; akpm@linux-foundation.org; axboe@kernel.dk;
> christian.brauner@ubuntu.com; containers@lists.linux-foundation.org;
> jannh@google.com; keescook@chromium.org; kernel-
> hardening@lists.openwall.com; linux-kernel@vger.kernel.org; linux-
> mm@kvack.org; oleg@redhat.com; torvalds@linux-foundation.org
> Subject: Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of
> ucounts
> 
> On Tue, Aug 17, 2021 at 10:47:14AM -0500, Eric W. Biederman wrote:
> > "Ma, XinjianX" <xinjianx.ma@intel.com> writes:
> >
> > > Hi Alexey,
> > >
> > > When lkp team run kernel selftests, we found after these series of
> > > patches, testcase mqueue: mq_perf_tests in kselftest failed with
> following message.
> >
> > Which kernel was this run against?
> >
> > Where can the mq_perf_tests that you ran and had problems with be
> found?
> >
> > During your run were you using user namespaces as part of your test
> > environment?
> >
> > The error message too many files corresponds to the error code EMFILES
> > which is the error code that is returned when the rlimit is reached.
> >
> > One possibility is that your test environment was run in a user
> > namespace and so you wound up limited by rlimit of the user who
> > created the user namespace at the point of user namespace creation.
> >
> > At this point if you can give us enough information to look into this
> > and attempt to reproduce it that would be appreciated.
> 
> I was able to reproduce it on master without using user namespace.
> I suspect that the maximum value is not assigned here [1]:
> 
> set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,
> task_rlimit(&init_task, RLIMIT_MSGQUEUE));
> 
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kerne
> l/fork.c#n832
Thank you for confirming the issue. And will you plan to fix this issue?
If it's your plan, kindly add following tag as appropriate
Reported-by: kernel test robot <xinjianx.ma@intel.com>


> 
> > > If you confirm and fix the issue, kindly add following tag as
> > > appropriate
> > > Reported-by: kernel test robot lkp@intel.com
> > >
> > > ```
> > > # selftests: mqueue: mq_perf_tests
> > > #
> > > # Initial system state:
> > > #       Using queue path:                       /mq_perf_tests
> > > #       RLIMIT_MSGQUEUE(soft):                  819200
> > > #       RLIMIT_MSGQUEUE(hard):                  819200
> > > #       Maximum Message Size:                   8192
> > > #       Maximum Queue Size:                     10
> > > #       Nice value:                             0
> > > #
> > > # Adjusted system state for testing:
> > > #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> > > #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> > > #       Maximum Message Size:                   16777216
> > > #       Maximum Queue Size:                     65530
> > > #       Nice value:                             -20
> > > #       Continuous mode:                        (disabled)
> > > #       CPUs to pin:                            3
> > > # ./mq_perf_tests: mq_open() at 296: Too many open files not ok 2
> > > selftests: mqueue: mq_perf_tests # exit=1
> > > ```
> > >
> > > Test env:
> > > rootfs: debian-10
> > > gcc version: 9
> > >
> > > ------
> > > Thanks
> > > Ma Xinjian
> >
> > Eric
> >
> 
> --
> Rgrds, legion

Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Eric W. Biederman]

Alexey Gladkov <legion@kernel.org> writes:

> On Tue, Aug 17, 2021 at 10:47:14AM -0500, Eric W. Biederman wrote:
>> "Ma, XinjianX" <xinjianx.ma@intel.com> writes:
>> 
>> > Hi Alexey,
>> >
>> > When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
>> > in kselftest failed with following message.
>> 
>> Which kernel was this run against?
>> 
>> Where can the mq_perf_tests that you ran and had problems with be found?
>> 
>> During your run were you using user namespaces as part of your test
>> environment?
>> 
>> The error message too many files corresponds to the error code EMFILES
>> which is the error code that is returned when the rlimit is reached.
>> 
>> One possibility is that your test environment was run in a user
>> namespace and so you wound up limited by rlimit of the user who created
>> the user namespace at the point of user namespace creation. 
>> 
>> At this point if you can give us enough information to look into this
>> and attempt to reproduce it that would be appreciated.
>
> I was able to reproduce it on master without using user namespace.
> I suspect that the maximum value is not assigned here [1]:
>
> set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/fork.c#n832

The rlimits for init_task are set to INIT_RLIMITS.
In INIT_RLIMITS RLIMIT_MSGQUEUE is set to MQ_MAX_BYTES

So that definitely means that as the code is current constructed the
rlimit can not be effectively raised.

So it looks like we are just silly and preventing the initial rlimits
from being raised.

So we probably want to do something like:

diff --git a/kernel/fork.c b/kernel/fork.c
index bc94b2cc5995..557ce0083ba3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -825,13 +825,13 @@ void __init fork_init(void)
 	init_task.signal->rlim[RLIMIT_SIGPENDING] =
 		init_task.signal->rlim[RLIMIT_NPROC];
 
+	/* For non-rlimit ucounts make their default limit max_threads/2 */
 	for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
 		init_user_ns.ucount_max[i] = max_threads/2;
 
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, task_rlimit(&init_task, RLIMIT_NPROC));
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING));
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, task_rlimit(&init_task, RLIMIT_MEMLOCK));
+	/* In init_user_ns default rlimit to be the only limit */
+	for (; i < UCOUNT_COUNTS; i++)
+		set_rlimit_ucount_max(&init_user_ns, i, RLIMIT_INFINITY);
 
 #ifdef CONFIG_VMAP_STACK
 	cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",


Eric

Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Alexey Gladkov]

On Thu, Aug 19, 2021 at 10:10:26AM -0500, Eric W. Biederman wrote:
> Alexey Gladkov <legion@kernel.org> writes:
> 
> > On Tue, Aug 17, 2021 at 10:47:14AM -0500, Eric W. Biederman wrote:
> >> "Ma, XinjianX" <xinjianx.ma@intel.com> writes:
> >> 
> >> > Hi Alexey,
> >> >
> >> > When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
> >> > in kselftest failed with following message.
> >> 
> >> Which kernel was this run against?
> >> 
> >> Where can the mq_perf_tests that you ran and had problems with be found?
> >> 
> >> During your run were you using user namespaces as part of your test
> >> environment?
> >> 
> >> The error message too many files corresponds to the error code EMFILES
> >> which is the error code that is returned when the rlimit is reached.
> >> 
> >> One possibility is that your test environment was run in a user
> >> namespace and so you wound up limited by rlimit of the user who created
> >> the user namespace at the point of user namespace creation. 
> >> 
> >> At this point if you can give us enough information to look into this
> >> and attempt to reproduce it that would be appreciated.
> >
> > I was able to reproduce it on master without using user namespace.
> > I suspect that the maximum value is not assigned here [1]:
> >
> > set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));
> >
> > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/fork.c#n832
> 
> The rlimits for init_task are set to INIT_RLIMITS.
> In INIT_RLIMITS RLIMIT_MSGQUEUE is set to MQ_MAX_BYTES
> 
> So that definitely means that as the code is current constructed the
> rlimit can not be effectively raised.
> 
> So it looks like we are just silly and preventing the initial rlimits
> from being raised.
> 
> So we probably want to do something like:

Damn, you are faster than me! :)

> diff --git a/kernel/fork.c b/kernel/fork.c
> index bc94b2cc5995..557ce0083ba3 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -825,13 +825,13 @@ void __init fork_init(void)
>  	init_task.signal->rlim[RLIMIT_SIGPENDING] =
>  		init_task.signal->rlim[RLIMIT_NPROC];
>  
> +	/* For non-rlimit ucounts make their default limit max_threads/2 */
>  	for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
>  		init_user_ns.ucount_max[i] = max_threads/2;
>  
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, task_rlimit(&init_task, RLIMIT_NPROC));
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING));
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, task_rlimit(&init_task, RLIMIT_MEMLOCK));
> +	/* In init_user_ns default rlimit to be the only limit */
> +	for (; i < UCOUNT_COUNTS; i++)
> +		set_rlimit_ucount_max(&init_user_ns, i, RLIMIT_INFINITY);

s/RLIMIT_INFINITY/RLIM_INFINITY/

>  
>  #ifdef CONFIG_VMAP_STACK
>  	cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
> 

Acked-by: Alexey Gladkov <legion@kernel.org>

I cannot complete this test on my laptop. On 4Gb, the test ends with
oom-killer. But with this patch, the test definitely passes the moment of
the previous fall.

-- 
Rgrds, legion

[PATCH] ucounts: Fix regression preventing increasing of rlimits in init_user_ns

[Eric W. Biederman]

"Ma, XinjianX" <xinjianx.ma@intel.com> reported:

> When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
> in kselftest failed with following message.
>
> # selftests: mqueue: mq_perf_tests
> #
> # Initial system state:
> #       Using queue path:                       /mq_perf_tests
> #       RLIMIT_MSGQUEUE(soft):                  819200
> #       RLIMIT_MSGQUEUE(hard):                  819200
> #       Maximum Message Size:                   8192
> #       Maximum Queue Size:                     10
> #       Nice value:                             0
> #
> # Adjusted system state for testing:
> #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> #       Maximum Message Size:                   16777216
> #       Maximum Queue Size:                     65530
> #       Nice value:                             -20
> #       Continuous mode:                        (disabled)
> #       CPUs to pin:                            3
> # ./mq_perf_tests: mq_open() at 296: Too many open files
> not ok 2 selftests: mqueue: mq_perf_tests # exit=1
> ```
>
> Test env:
> rootfs: debian-10
> gcc version: 9

After investigation the problem turned out to be that ucount_max for
the rlimits in init_user_ns was being set to the initial rlimit value.
The practical problem is that ucount_max provides a limit that
applications inside the user namespace can not exceed.  Which means in
practice that rlimits that have been converted to use the ucount
infrastructure were not able to exceend their initial rlimits.

Solve this by setting the relevant values of ucount_max to
RLIM_INIFINITY.  A limit in init_user_ns is pointless so the code
should allow the values to grow as large as possible without riscking
an underflow or an overflow.

As the ltp test case was a bit of a pain I have reproduced the rlimit failure
and tested the fix with the following little C program:
> #include <stdio.h>
> #include <fcntl.h>
> #include <sys/stat.h>
> #include <mqueue.h>
> #include <sys/time.h>
> #include <sys/resource.h>
> #include <errno.h>
> #include <string.h>
> #include <stdlib.h>
> #include <limits.h>
> #include <unistd.h>
>
> int main(int argc, char **argv)
> {
> 	struct mq_attr mq_attr;
> 	struct rlimit rlim;
> 	mqd_t mqd;
> 	int ret;
>
> 	ret = getrlimit(RLIMIT_MSGQUEUE, &rlim);
> 	if (ret != 0) {
> 		fprintf(stderr, "getrlimit(RLIMIT_MSGQUEUE) failed: %s\n", strerror(errno));
> 		exit(EXIT_FAILURE);
> 	}
> 	printf("RLIMIT_MSGQUEUE %lu %lu\n",
> 	       rlim.rlim_cur, rlim.rlim_max);
> 	rlim.rlim_cur = RLIM_INFINITY;
> 	rlim.rlim_max = RLIM_INFINITY;
> 	ret = setrlimit(RLIMIT_MSGQUEUE, &rlim);
> 	if (ret != 0) {
> 		fprintf(stderr, "setrlimit(RLIMIT_MSGQUEUE, RLIM_INFINITY) failed: %s\n", strerror(errno));
> 		exit(EXIT_FAILURE);
> 	}
>
> 	memset(&mq_attr, 0, sizeof(struct mq_attr));
> 	mq_attr.mq_maxmsg = 65536 - 1;
> 	mq_attr.mq_msgsize = 16*1024*1024 - 1;
>
> 	mqd = mq_open("/mq_rlimit_test", O_RDONLY|O_CREAT, 0600, &mq_attr);
> 	if (mqd == (mqd_t)-1) {
> 		fprintf(stderr, "mq_open failed: %s\n", strerror(errno));
> 		exit(EXIT_FAILURE);
> 	}
> 	ret = mq_close(mqd);
> 	if (ret) {
> 		fprintf(stderr, "mq_close failed; %s\n", strerror(errno));
> 		exit(EXIT_FAILURE);
> 	}
>
> 	return EXIT_SUCCESS;
> }

Fixes: 6e52a9f0532f ("Reimplement RLIMIT_MSGQUEUE on top of ucounts")
Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts")
Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts")
Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts")
Reported-by: kernel test robot lkp@intel.com
Acked-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---

This is a simplified version of my previous change that I have tested
and will push out to linux-next and then to Linus shortly.

 kernel/fork.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index bc94b2cc5995..44f4c2d83763 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -828,10 +828,10 @@ void __init fork_init(void)
 	for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
 		init_user_ns.ucount_max[i] = max_threads/2;
 
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, task_rlimit(&init_task, RLIMIT_NPROC));
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING));
-	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, task_rlimit(&init_task, RLIMIT_MEMLOCK));
+	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,      RLIM_INFINITY);
+	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,   RLIM_INFINITY);
+	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
+	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,    RLIM_INFINITY);
 
 #ifdef CONFIG_VMAP_STACK
 	cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
-- 
2.20.1

RE: [PATCH] ucounts: Fix regression preventing increasing of rlimits in init_user_ns

[Ma, XinjianX]

> -----Original Message-----
> From: Eric W. Biederman <ebiederm@xmission.com>
> Sent: Tuesday, August 24, 2021 5:07 AM
> To: Alexey Gladkov <legion@kernel.org>
> Cc: Ma, XinjianX <xinjianx.ma@intel.com>; linux-kselftest@vger.kernel.org;
> lkp <lkp@intel.com>; akpm@linux-foundation.org; axboe@kernel.dk;
> christian.brauner@ubuntu.com; containers@lists.linux-foundation.org;
> jannh@google.com; keescook@chromium.org; kernel-
> hardening@lists.openwall.com; linux-kernel@vger.kernel.org; linux-
> mm@kvack.org; oleg@redhat.com; torvalds@linux-foundation.org
> Subject: [PATCH] ucounts: Fix regression preventing increasing of rlimits in
> init_user_ns
> 
> 
> "Ma, XinjianX" <xinjianx.ma@intel.com> reported:
> 
> > When lkp team run kernel selftests, we found after these series of
> > patches, testcase mqueue: mq_perf_tests in kselftest failed with following
> message.
> >
> > # selftests: mqueue: mq_perf_tests
> > #
> > # Initial system state:
> > #       Using queue path:                       /mq_perf_tests
> > #       RLIMIT_MSGQUEUE(soft):                  819200
> > #       RLIMIT_MSGQUEUE(hard):                  819200
> > #       Maximum Message Size:                   8192
> > #       Maximum Queue Size:                     10
> > #       Nice value:                             0
> > #
> > # Adjusted system state for testing:
> > #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> > #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> > #       Maximum Message Size:                   16777216
> > #       Maximum Queue Size:                     65530
> > #       Nice value:                             -20
> > #       Continuous mode:                        (disabled)
> > #       CPUs to pin:                            3
> > # ./mq_perf_tests: mq_open() at 296: Too many open files not ok 2
> > selftests: mqueue: mq_perf_tests # exit=1 ```
> >
> > Test env:
> > rootfs: debian-10
> > gcc version: 9
> 
> After investigation the problem turned out to be that ucount_max for the
> rlimits in init_user_ns was being set to the initial rlimit value.
> The practical problem is that ucount_max provides a limit that applications
> inside the user namespace can not exceed.  Which means in practice that
> rlimits that have been converted to use the ucount infrastructure were not
> able to exceend their initial rlimits.
> 
> Solve this by setting the relevant values of ucount_max to RLIM_INIFINITY.  A
> limit in init_user_ns is pointless so the code should allow the values to grow
> as large as possible without riscking an underflow or an overflow.
> 
> As the ltp test case was a bit of a pain I have reproduced the rlimit failure and
> tested the fix with the following little C program:
> > #include <stdio.h>
> > #include <fcntl.h>
> > #include <sys/stat.h>
> > #include <mqueue.h>
> > #include <sys/time.h>
> > #include <sys/resource.h>
> > #include <errno.h>
> > #include <string.h>
> > #include <stdlib.h>
> > #include <limits.h>
> > #include <unistd.h>
> >
> > int main(int argc, char **argv)
> > {
> > 	struct mq_attr mq_attr;
> > 	struct rlimit rlim;
> > 	mqd_t mqd;
> > 	int ret;
> >
> > 	ret = getrlimit(RLIMIT_MSGQUEUE, &rlim);
> > 	if (ret != 0) {
> > 		fprintf(stderr, "getrlimit(RLIMIT_MSGQUEUE) failed: %s\n",
> strerror(errno));
> > 		exit(EXIT_FAILURE);
> > 	}
> > 	printf("RLIMIT_MSGQUEUE %lu %lu\n",
> > 	       rlim.rlim_cur, rlim.rlim_max);
> > 	rlim.rlim_cur = RLIM_INFINITY;
> > 	rlim.rlim_max = RLIM_INFINITY;
> > 	ret = setrlimit(RLIMIT_MSGQUEUE, &rlim);
> > 	if (ret != 0) {
> > 		fprintf(stderr, "setrlimit(RLIMIT_MSGQUEUE, RLIM_INFINITY)
> failed: %s\n", strerror(errno));
> > 		exit(EXIT_FAILURE);
> > 	}
> >
> > 	memset(&mq_attr, 0, sizeof(struct mq_attr));
> > 	mq_attr.mq_maxmsg = 65536 - 1;
> > 	mq_attr.mq_msgsize = 16*1024*1024 - 1;
> >
> > 	mqd = mq_open("/mq_rlimit_test", O_RDONLY|O_CREAT, 0600,
> &mq_attr);
> > 	if (mqd == (mqd_t)-1) {
> > 		fprintf(stderr, "mq_open failed: %s\n", strerror(errno));
> > 		exit(EXIT_FAILURE);
> > 	}
> > 	ret = mq_close(mqd);
> > 	if (ret) {
> > 		fprintf(stderr, "mq_close failed; %s\n", strerror(errno));
> > 		exit(EXIT_FAILURE);
> > 	}
> >
> > 	return EXIT_SUCCESS;
> > }
> 
> Fixes: 6e52a9f0532f ("Reimplement RLIMIT_MSGQUEUE on top of ucounts")
> Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts")
> Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts")
> Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts")
> Reported-by: kernel test robot lkp@intel.com
Sorry, but <> around email address is needed 
Reported-by: kernel test robot <lkp@intel.com>

> Acked-by: Alexey Gladkov <legion@kernel.org>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
> 
> This is a simplified version of my previous change that I have tested and will
> push out to linux-next and then to Linus shortly.
> 
>  kernel/fork.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/fork.c b/kernel/fork.c index bc94b2cc5995..44f4c2d83763
> 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -828,10 +828,10 @@ void __init fork_init(void)
>  	for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
>  		init_user_ns.ucount_max[i] = max_threads/2;
> 
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,
> task_rlimit(&init_task, RLIMIT_NPROC));
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,
> task_rlimit(&init_task, RLIMIT_MSGQUEUE));
> -	set_rlimit_ucount_max(&init_user_ns,
> UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING));
> -	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,
> task_rlimit(&init_task, RLIMIT_MEMLOCK));
> +	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,
> RLIM_INFINITY);
> +	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,
> RLIM_INFINITY);
> +	set_rlimit_ucount_max(&init_user_ns,
> UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
> +	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,
> RLIM_INFINITY);
> 
>  #ifdef CONFIG_VMAP_STACK
>  	cpuhp_setup_state(CPUHP_BP_PREPARE_DYN,
> "fork:vm_stack_cache",
> --
> 2.20.1

Re: [PATCH] ucounts: Fix regression preventing increasing of rlimits in init_user_ns

[Eric W. Biederman]

"Ma, XinjianX" <xinjianx.ma@intel.com> writes:

>> -----Original Message-----
>> From: Eric W. Biederman <ebiederm@xmission.com>
>> ...
>> Reported-by: kernel test robot lkp@intel.com
> Sorry, but <> around email address is needed 
> Reported-by: kernel test robot <lkp@intel.com>

The change is already tested and pushed out so I really don't want to
mess with it.  Especially as I am aiming to send it to Linus on
Wednesday after it has had a chance to pass through linux-next and
whatever automated tests are there.

What does copying and pasting the Reported-by: tag as included in
your original report cause to break?

At this point I suspect that the danger of fat fingering something
far outweighs whatever benefits might be gained by surrounding the
email address with <> marks.

Eric