[v2] Allow to change ipc/mq sysctls inside ipc namespace

[PATCH v2 1/3] sysctl: Allow change system v ipc sysctls inside ipc namespace

Posted by Alexey Gladkov 3 years, 6 months ago

Rootless containers are not allowed to modify kernel IPC parameters.

All default limits are set to such high values that in fact there are no
limits at all. All limits are not inherited and are initialized to
default values when a new ipc_namespace is created.

For new ipc_namespace:

size_t       ipc_ns.shm_ctlmax = SHMMAX; // (ULONG_MAX - (1UL << 24))
size_t       ipc_ns.shm_ctlall = SHMALL; // (ULONG_MAX - (1UL << 24))
int          ipc_ns.shm_ctlmni = IPCMNI; // (1 << 15)
int          ipc_ns.shm_rmid_forced = 0;
unsigned int ipc_ns.msg_ctlmax = MSGMAX; // 8192
unsigned int ipc_ns.msg_ctlmni = MSGMNI; // 32000
unsigned int ipc_ns.msg_ctlmnb = MSGMNB; // 16384

The shm_tot (total amount of shared pages) has also ceased to be
global, it is located in ipc_namespace and is not inherited from
anywhere.

In such conditions, it cannot be said that these limits limit anything.
The real limiter for them is cgroups.

If we allow rootless containers to change these parameters, then it can
only be reduced.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
 ipc/ipc_sysctl.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index ef313ecfb53a..a6a9d7f680dd 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -190,25 +190,53 @@ static int set_is_seen(struct ctl_table_set *set)
 	return &current->nsproxy->ipc_ns->ipc_set == set;
 }
 
+static void ipc_set_ownership(struct ctl_table_header *head,
+			      struct ctl_table *table,
+			      kuid_t *uid, kgid_t *gid)
+{
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
+
+	kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+	kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+	*uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+	*gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
 static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)
 {
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
 	int mode = table->mode;
+	kuid_t ns_root_uid;
+	kgid_t ns_root_gid;
 
-#ifdef CONFIG_CHECKPOINT_RESTORE
-	struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+	ipc_set_ownership(head, table, &ns_root_uid, ns_root_gid);
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
 	if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&
 	    checkpoint_restore_ns_capable(ns->user_ns))
 		mode = 0666;
+	else
 #endif
-	return mode;
+	if (uid_eq(current_euid(), ns_root_uid))
+		mode >>= 6;
+
+	else if (in_egroup_p(ns_root_gid))
+		mode >>= 3;
+
+	mode &= 7;
+
+	return (mode << 6) | (mode << 3) | mode;
 }
 
 static struct ctl_table_root set_root = {
 	.lookup = set_lookup,
 	.permissions = ipc_permissions,
+	.set_ownership = ipc_set_ownership,
 };
 
 bool setup_ipc_sysctls(struct ipc_namespace *ns)
-- 
2.33.4

Re: [PATCH v2 1/3] sysctl: Allow change system v ipc sysctls inside ipc namespace

Posted by kernel test robot 3 years, 6 months ago

Hi Alexey,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on kees/for-next/pstore linus/master v6.0-rc6 next-20220920]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexey-Gladkov/sysctl-Allow-change-system-v-ipc-sysctls-inside-ipc-namespace/20220921-030939
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: hexagon-randconfig-r041-20220921 (https://download.01.org/0day-ci/archive/20220921/202209211737.0Bu0F40t-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/eb972fb9aad60123519d8dd32df26cb58985ce4a
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Alexey-Gladkov/sysctl-Allow-change-system-v-ipc-sysctls-inside-ipc-namespace/20220921-030939
        git checkout eb972fb9aad60123519d8dd32df26cb58985ce4a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> ipc/ipc_sysctl.c:215:47: error: passing 'kgid_t' to parameter of incompatible type 'kgid_t *'; take the address with &
           ipc_set_ownership(head, table, &ns_root_uid, ns_root_gid);
                                                        ^~~~~~~~~~~
                                                        &
   ipc/ipc_sysctl.c:195:31: note: passing argument to parameter 'gid' here
                                 kuid_t *uid, kgid_t *gid)
                                                      ^
>> ipc/ipc_sysctl.c:225:13: error: call to undeclared function 'current_euid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           if (uid_eq(current_euid(), ns_root_uid))
                      ^
   ipc/ipc_sysctl.c:225:13: note: did you mean 'current_work'?
   include/linux/workqueue.h:467:28: note: 'current_work' declared here
   extern struct work_struct *current_work(void);
                              ^
>> ipc/ipc_sysctl.c:225:13: error: passing 'int' to parameter of incompatible type 'kuid_t'
           if (uid_eq(current_euid(), ns_root_uid))
                      ^~~~~~~~~~~~~~
   include/linux/uidgid.h:61:34: note: passing argument to parameter 'left' here
   static inline bool uid_eq(kuid_t left, kuid_t right)
                                    ^
>> ipc/ipc_sysctl.c:228:11: error: call to undeclared function 'in_egroup_p'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           else if (in_egroup_p(ns_root_gid))
                    ^
   4 errors generated.


vim +215 ipc/ipc_sysctl.c

   206	
   207	static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)
   208	{
   209		struct ipc_namespace *ns =
   210			container_of(head->set, struct ipc_namespace, ipc_set);
   211		int mode = table->mode;
   212		kuid_t ns_root_uid;
   213		kgid_t ns_root_gid;
   214	
 > 215		ipc_set_ownership(head, table, &ns_root_uid, ns_root_gid);
   216	
   217	#ifdef CONFIG_CHECKPOINT_RESTORE
   218		if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||
   219		     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||
   220		     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&
   221		    checkpoint_restore_ns_capable(ns->user_ns))
   222			mode = 0666;
   223		else
   224	#endif
 > 225		if (uid_eq(current_euid(), ns_root_uid))
   226			mode >>= 6;
   227	
 > 228		else if (in_egroup_p(ns_root_gid))
   229			mode >>= 3;
   230	
   231		mode &= 7;
   232	
   233		return (mode << 6) | (mode << 3) | mode;
   234	}
   235	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

[PATCH v3 0/3] Allow to change ipc/mq sysctls inside ipc namespace

Posted by Alexey Gladkov 3 years, 6 months ago

Right now ipc and mq limits count as per ipc namespace, but only real
root can change them. By default, the current values of these limits are
such that it can only be reduced. Since only root can change the values,
it is impossible to reduce these limits in the rootless container.

We can allow limit changes within ipc namespace because mq parameters
are limited by RLIMIT_MSGQUEUE and ipc parameters are not limited to
anything other than cgroups.

--

Alexey Gladkov (3):
  sysctl: Allow change system v ipc sysctls inside ipc namespace
  sysctl: Allow to change limits for posix messages queues
  docs: Add information about ipc sysctls limitations

 Documentation/admin-guide/sysctl/kernel.rst | 14 ++++++--
 ipc/ipc_sysctl.c                            | 36 +++++++++++++++++++--
 ipc/mq_sysctl.c                             | 36 +++++++++++++++++++++
 3 files changed, 81 insertions(+), 5 deletions(-)

-- 
2.33.4

[RESEND PATCH v3 0/3] Allow to change ipc/mq sysctls inside ipc namespace

Posted by Alexey Gladkov 2 years, 2 months ago

Right now ipc and mq limits count as per ipc namespace, but only real
root can change them. By default, the current values of these limits are
such that it can only be reduced. Since only root can change the values,
it is impossible to reduce these limits in the rootless container.

We can allow limit changes within ipc namespace because mq parameters
are limited by RLIMIT_MSGQUEUE and ipc parameters are not limited to
anything other than cgroups.

This is just a rebase of patches on v6.7-6264-g70d201a40823.

---

Alexey Gladkov (3):
  sysctl: Allow change system v ipc sysctls inside ipc namespace
  docs: Add information about ipc sysctls limitations
  sysctl: Allow to change limits for posix messages queues

 Documentation/admin-guide/sysctl/kernel.rst | 14 ++++++--
 ipc/ipc_sysctl.c                            | 37 +++++++++++++++++++--
 ipc/mq_sysctl.c                             | 36 ++++++++++++++++++++
 3 files changed, 82 insertions(+), 5 deletions(-)

-- 
2.43.0

[RESEND PATCH v3 1/3] sysctl: Allow change system v ipc sysctls inside ipc namespace

Posted by Alexey Gladkov 2 years, 2 months ago

Rootless containers are not allowed to modify kernel IPC parameters.

All default limits are set to such high values that in fact there are no
limits at all. All limits are not inherited and are initialized to
default values when a new ipc_namespace is created.

For new ipc_namespace:

size_t       ipc_ns.shm_ctlmax = SHMMAX; // (ULONG_MAX - (1UL << 24))
size_t       ipc_ns.shm_ctlall = SHMALL; // (ULONG_MAX - (1UL << 24))
int          ipc_ns.shm_ctlmni = IPCMNI; // (1 << 15)
int          ipc_ns.shm_rmid_forced = 0;
unsigned int ipc_ns.msg_ctlmax = MSGMAX; // 8192
unsigned int ipc_ns.msg_ctlmni = MSGMNI; // 32000
unsigned int ipc_ns.msg_ctlmnb = MSGMNB; // 16384

The shm_tot (total amount of shared pages) has also ceased to be
global, it is located in ipc_namespace and is not inherited from
anywhere.

In such conditions, it cannot be said that these limits limit anything.
The real limiter for them is cgroups.

If we allow rootless containers to change these parameters, then it can
only be reduced.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/e2d84d3ec0172cfff759e6065da84ce0cc2736f8.1663756794.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 ipc/ipc_sysctl.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 8c62e443f78b..01c4a50d22b2 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -14,6 +14,7 @@
 #include <linux/ipc_namespace.h>
 #include <linux/msg.h>
 #include <linux/slab.h>
+#include <linux/cred.h>
 #include "util.h"
 
 static int proc_ipc_dointvec_minmax_orphans(struct ctl_table *table, int write,
@@ -190,25 +191,57 @@ static int set_is_seen(struct ctl_table_set *set)
 	return &current->nsproxy->ipc_ns->ipc_set == set;
 }
 
+static void ipc_set_ownership(struct ctl_table_header *head,
+			      struct ctl_table *table,
+			      kuid_t *uid, kgid_t *gid)
+{
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
+
+	kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+	kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+	*uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+	*gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
 static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)
 {
 	int mode = table->mode;
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
-	struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
 
 	if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&
 	    checkpoint_restore_ns_capable(ns->user_ns))
 		mode = 0666;
+	else
 #endif
-	return mode;
+	{
+		kuid_t ns_root_uid;
+		kgid_t ns_root_gid;
+
+		ipc_set_ownership(head, table, &ns_root_uid, &ns_root_gid);
+
+		if (uid_eq(current_euid(), ns_root_uid))
+			mode >>= 6;
+
+		else if (in_egroup_p(ns_root_gid))
+			mode >>= 3;
+	}
+
+	mode &= 7;
+
+	return (mode << 6) | (mode << 3) | mode;
 }
 
 static struct ctl_table_root set_root = {
 	.lookup = set_lookup,
 	.permissions = ipc_permissions,
+	.set_ownership = ipc_set_ownership,
 };
 
 bool setup_ipc_sysctls(struct ipc_namespace *ns)
-- 
2.43.0

[RESEND PATCH v3 2/3] docs: Add information about ipc sysctls limitations

Posted by Alexey Gladkov 2 years, 2 months ago

After 25b21cb2f6d6 ("[PATCH] IPC namespace core") and 4e9823111bdc
("[PATCH] IPC namespace - shm") the shared memory page count stopped
being global and started counting per ipc namespace. The documentation
and shmget(2) still says that shmall is a global option.

shmget(2):

SHMALL System-wide limit on the total amount of shared memory, measured
in units of the system page size. On Linux, this limit can be read and
modified via /proc/sys/kernel/shmall.

I think the changes made in 2006 should be documented.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lkml.kernel.org/r/ede20ddf7be48b93e8084c3be2e920841ee1a641.1663756794.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 Documentation/admin-guide/sysctl/kernel.rst | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 6584a1f9bfe3..bc578663619d 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -594,6 +594,9 @@ default (``MSGMNB``).
 ``msgmni`` is the maximum number of IPC queues. 32000 by default
 (``MSGMNI``).
 
+All of these parameters are set per ipc namespace. The maximum number of bytes
+in POSIX message queues is limited by ``RLIMIT_MSGQUEUE``. This limit is
+respected hierarchically in the each user namespace.
 
 msg_next_id, sem_next_id, and shm_next_id (System V IPC)
 ========================================================
@@ -1274,15 +1277,20 @@ are doing anyway :)
 shmall
 ======
 
-This parameter sets the total amount of shared memory pages that
-can be used system wide. Hence, ``shmall`` should always be at least
-``ceil(shmmax/PAGE_SIZE)``.
+This parameter sets the total amount of shared memory pages that can be used
+inside ipc namespace. The shared memory pages counting occurs for each ipc
+namespace separately and is not inherited. Hence, ``shmall`` should always be at
+least ``ceil(shmmax/PAGE_SIZE)``.
 
 If you are not sure what the default ``PAGE_SIZE`` is on your Linux
 system, you can run the following command::
 
 	# getconf PAGE_SIZE
 
+To reduce or disable the ability to allocate shared memory, you must create a
+new ipc namespace, set this parameter to the required value and prohibit the
+creation of a new ipc namespace in the current user namespace or cgroups can
+be used.
 
 shmmax
 ======
-- 
2.43.0

[RESEND PATCH v3 3/3] sysctl: Allow to change limits for posix messages queues

Posted by Alexey Gladkov 2 years, 2 months ago

All parameters of posix messages queues (queues_max/msg_max/msgsize_max)
end up being limited by RLIMIT_MSGQUEUE. The code in mqueue_get_inode is
where that limiting happens.

The RLIMIT_MSGQUEUE is bound to the user namespace and is counted
hierarchically.

We can allow root in the user namespace to modify the posix messages
queues parameters.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/7eb21211c8622e91d226e63416b1b93c079f60ee.1663756794.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 ipc/mq_sysctl.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index ebb5ed81c151..21fba3a6edaf 100644
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -12,6 +12,7 @@
 #include <linux/stat.h>
 #include <linux/capability.h>
 #include <linux/slab.h>
+#include <linux/cred.h>
 
 static int msg_max_limit_min = MIN_MSGMAX;
 static int msg_max_limit_max = HARD_MSGMAX;
@@ -76,8 +77,43 @@ static int set_is_seen(struct ctl_table_set *set)
 	return &current->nsproxy->ipc_ns->mq_set == set;
 }
 
+static void mq_set_ownership(struct ctl_table_header *head,
+			     struct ctl_table *table,
+			     kuid_t *uid, kgid_t *gid)
+{
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, mq_set);
+
+	kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+	kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+	*uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+	*gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
+static int mq_permissions(struct ctl_table_header *head, struct ctl_table *table)
+{
+	int mode = table->mode;
+	kuid_t ns_root_uid;
+	kgid_t ns_root_gid;
+
+	mq_set_ownership(head, table, &ns_root_uid, &ns_root_gid);
+
+	if (uid_eq(current_euid(), ns_root_uid))
+		mode >>= 6;
+
+	else if (in_egroup_p(ns_root_gid))
+		mode >>= 3;
+
+	mode &= 7;
+
+	return (mode << 6) | (mode << 3) | mode;
+}
+
 static struct ctl_table_root set_root = {
 	.lookup = set_lookup,
+	.permissions = mq_permissions,
+	.set_ownership = mq_set_ownership,
 };
 
 bool setup_mq_sysctls(struct ipc_namespace *ns)
-- 
2.43.0

[PATCH v3 1/3] sysctl: Allow change system v ipc sysctls inside ipc namespace

Posted by Alexey Gladkov 3 years, 6 months ago

Rootless containers are not allowed to modify kernel IPC parameters.

All default limits are set to such high values that in fact there are no
limits at all. All limits are not inherited and are initialized to
default values when a new ipc_namespace is created.

For new ipc_namespace:

size_t       ipc_ns.shm_ctlmax = SHMMAX; // (ULONG_MAX - (1UL << 24))
size_t       ipc_ns.shm_ctlall = SHMALL; // (ULONG_MAX - (1UL << 24))
int          ipc_ns.shm_ctlmni = IPCMNI; // (1 << 15)
int          ipc_ns.shm_rmid_forced = 0;
unsigned int ipc_ns.msg_ctlmax = MSGMAX; // 8192
unsigned int ipc_ns.msg_ctlmni = MSGMNI; // 32000
unsigned int ipc_ns.msg_ctlmnb = MSGMNB; // 16384

The shm_tot (total amount of shared pages) has also ceased to be
global, it is located in ipc_namespace and is not inherited from
anywhere.

In such conditions, it cannot be said that these limits limit anything.
The real limiter for them is cgroups.

If we allow rootless containers to change these parameters, then it can
only be reduced.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
 ipc/ipc_sysctl.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index ef313ecfb53a..31282e0a630d 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -190,25 +190,57 @@ static int set_is_seen(struct ctl_table_set *set)
 	return &current->nsproxy->ipc_ns->ipc_set == set;
 }
 
+static void ipc_set_ownership(struct ctl_table_header *head,
+			      struct ctl_table *table,
+			      kuid_t *uid, kgid_t *gid)
+{
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
+
+	kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+	kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+	*uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+	*gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
 static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)
 {
 	int mode = table->mode;
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
-	struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
 
 	if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&
 	    checkpoint_restore_ns_capable(ns->user_ns))
 		mode = 0666;
+	else
 #endif
-	return mode;
+	{
+		kuid_t ns_root_uid;
+		kgid_t ns_root_gid;
+
+		ipc_set_ownership(head, table, &ns_root_uid, &ns_root_gid);
+
+		if (uid_eq(current_euid(), ns_root_uid))
+			mode >>= 6;
+
+		else if (in_egroup_p(ns_root_gid))
+			mode >>= 3;
+	}
+
+	mode &= 7;
+
+	return (mode << 6) | (mode << 3) | mode;
 }
 
 static struct ctl_table_root set_root = {
 	.lookup = set_lookup,
 	.permissions = ipc_permissions,
+	.set_ownership = ipc_set_ownership,
 };
 
 bool setup_ipc_sysctls(struct ipc_namespace *ns)
-- 
2.33.4

[PATCH v3 2/3] sysctl: Allow to change limits for posix messages queues

Posted by Alexey Gladkov 3 years, 6 months ago

All parameters of posix messages queues (queues_max/msg_max/msgsize_max)
end up being limited by RLIMIT_MSGQUEUE. The code in mqueue_get_inode is
where that limiting happens.

The RLIMIT_MSGQUEUE is bound to the user namespace and is counted
hierarchically.

We can allow root in the user namespace to modify the posix messages
queues parameters.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
 ipc/mq_sysctl.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index fbf6a8b93a26..ff1054fbbacc 100644
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -12,6 +12,7 @@
 #include <linux/stat.h>
 #include <linux/capability.h>
 #include <linux/slab.h>
+#include <linux/cred.h>
 
 static int msg_max_limit_min = MIN_MSGMAX;
 static int msg_max_limit_max = HARD_MSGMAX;
@@ -76,8 +77,43 @@ static int set_is_seen(struct ctl_table_set *set)
 	return &current->nsproxy->ipc_ns->mq_set == set;
 }
 
+static void mq_set_ownership(struct ctl_table_header *head,
+			     struct ctl_table *table,
+			     kuid_t *uid, kgid_t *gid)
+{
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, mq_set);
+
+	kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+	kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+	*uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+	*gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
+static int mq_permissions(struct ctl_table_header *head, struct ctl_table *table)
+{
+	int mode = table->mode;
+	kuid_t ns_root_uid;
+	kgid_t ns_root_gid;
+
+	mq_set_ownership(head, table, &ns_root_uid, &ns_root_gid);
+
+	if (uid_eq(current_euid(), ns_root_uid))
+		mode >>= 6;
+
+	if (in_egroup_p(ns_root_gid))
+		mode >>= 3;
+
+	mode &= 7;
+
+	return (mode << 6) | (mode << 3) | mode;
+}
+
 static struct ctl_table_root set_root = {
 	.lookup = set_lookup,
+	.permissions = mq_permissions,
+	.set_ownership = mq_set_ownership,
 };
 
 bool setup_mq_sysctls(struct ipc_namespace *ns)
-- 
2.33.4

[PATCH v3 3/3] docs: Add information about ipc sysctls limitations

Posted by Alexey Gladkov 3 years, 6 months ago

After 25b21cb2f6d6 ("[PATCH] IPC namespace core") and 4e9823111bdc
("[PATCH] IPC namespace - shm") the shared memory page count stopped
being global and started counting per ipc namespace. The documentation
and shmget(2) still says that shmall is a global option.

shmget(2):

SHMALL System-wide limit on the total amount of shared memory, measured
in units of the system page size. On Linux, this limit can be read and
modified via /proc/sys/kernel/shmall.

I think the changes made in 2006 should be documented.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 Documentation/admin-guide/sysctl/kernel.rst | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index ee6572b1edad..c8b89bd8f004 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -541,6 +541,9 @@ default (``MSGMNB``).
 ``msgmni`` is the maximum number of IPC queues. 32000 by default
 (``MSGMNI``).
 
+All of these parameters are set per ipc namespace. The maximum number of bytes
+in POSIX message queues is limited by ``RLIMIT_MSGQUEUE``. This limit is
+respected hierarchically in the each user namespace.
 
 msg_next_id, sem_next_id, and shm_next_id (System V IPC)
 ========================================================
@@ -1181,15 +1184,20 @@ are doing anyway :)
 shmall
 ======
 
-This parameter sets the total amount of shared memory pages that
-can be used system wide. Hence, ``shmall`` should always be at least
-``ceil(shmmax/PAGE_SIZE)``.
+This parameter sets the total amount of shared memory pages that can be used
+inside ipc namespace. The shared memory pages counting occurs for each ipc
+namespace separately and is not inherited. Hence, ``shmall`` should always be at
+least ``ceil(shmmax/PAGE_SIZE)``.
 
 If you are not sure what the default ``PAGE_SIZE`` is on your Linux
 system, you can run the following command::
 
 	# getconf PAGE_SIZE
 
+To reduce or disable the ability to allocate shared memory, you must create a
+new ipc namespace, set this parameter to the required value and prohibit the
+creation of a new ipc namespace in the current user namespace or cgroups can
+be used.
 
 shmmax
 ======
-- 
2.33.4