[RFC PATCH 2/4] sysctl: ipc: use typed fields for IPC namespace sysctls
From: Alexey Gladkov
Date: Sat Aug 29 2026 - 12:15:56 EST
IPC sysctl registration clones the table and rewrites data and limit
pointers for each namespace. This allocates a full ctl_table array per
namespace and ties the fixup loop to the table layout.
Describe the table with ctl_field offsets into ipc_namespace instead.
Keep the auto_msgmni entry data-less because its handler selects the
effective value itself. This removes the per-namespace table allocation
while preserving the existing handlers and limits.
Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx>
---
ipc/ipc_sysctl.c | 188 +++++++++++++++++++++--------------------------
1 file changed, 82 insertions(+), 106 deletions(-)
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 9b087ebeb643..f017b4109cc8 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -13,7 +13,6 @@
#include <linux/capability.h>
#include <linux/ipc_namespace.h>
#include <linux/msg.h>
-#include <linux/slab.h>
#include <linux/cred.h>
#include "util.h"
@@ -41,6 +40,8 @@ static int proc_ipc_auto_msgmni(const struct ctl_table *table, int write,
memcpy(&ipc_table, table, sizeof(ipc_table));
ipc_table.data = &dummy;
+ ipc_table.extra1 = SYSCTL_ZERO;
+ ipc_table.extra2 = SYSCTL_ONE;
if (write)
pr_info_once("writing to auto_msgmni has no effect");
@@ -72,110 +73,129 @@ static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,
int ipc_mni = IPCMNI;
int ipc_mni_shift = IPCMNI_SHIFT;
int ipc_min_cycle = RADIX_TREE_MAP_SIZE;
+static unsigned int ipc_mni_max = IPCMNI;
+static unsigned int ipc_uint_max = INT_MAX;
-static const struct ctl_table ipc_sysctls[] = {
+static const struct sysctl_field ipc_sysctls[] = {
{
.procname = "shmmax",
- .data = &init_ipc_ns.shm_ctlmax,
- .maxlen = sizeof(init_ipc_ns.shm_ctlmax),
.mode = 0644,
- .proc_handler = proc_doulongvec_minmax,
+ .type = SYSCTL_FIELD_SIZE_T,
+ .data_offset = SYSCTL_FIELD_SIZE_T_OFFSET(struct ipc_namespace,
+ shm_ctlmax),
},
{
.procname = "shmall",
- .data = &init_ipc_ns.shm_ctlall,
- .maxlen = sizeof(init_ipc_ns.shm_ctlall),
.mode = 0644,
- .proc_handler = proc_doulongvec_minmax,
+ .type = SYSCTL_FIELD_SIZE_T,
+ .data_offset = SYSCTL_FIELD_SIZE_T_OFFSET(struct ipc_namespace,
+ shm_ctlall),
},
{
.procname = "shmmni",
- .data = &init_ipc_ns.shm_ctlmni,
- .maxlen = sizeof(init_ipc_ns.shm_ctlmni),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = &ipc_mni,
+ .type = SYSCTL_FIELD_INT_MINMAX,
+ .data_offset = SYSCTL_FIELD_INT_OFFSET(struct ipc_namespace,
+ shm_ctlmni),
+ .int_limits = {
+ .min_value = SYSCTL_ZERO,
+ .max_value = &ipc_mni,
+ },
},
{
.procname = "shm_rmid_forced",
- .data = &init_ipc_ns.shm_rmid_forced,
- .maxlen = sizeof(init_ipc_ns.shm_rmid_forced),
.mode = 0644,
+ .type = SYSCTL_FIELD_INT_MINMAX,
.proc_handler = proc_ipc_dointvec_minmax_orphans,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_ONE,
+ .data_offset = SYSCTL_FIELD_INT_OFFSET(struct ipc_namespace,
+ shm_rmid_forced),
+ .int_limits = {
+ .min_value = SYSCTL_ZERO,
+ .max_value = SYSCTL_ONE,
+ },
},
{
.procname = "msgmax",
- .data = &init_ipc_ns.msg_ctlmax,
- .maxlen = sizeof(init_ipc_ns.msg_ctlmax),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_INT_MAX,
+ .type = SYSCTL_FIELD_UINT_MINMAX,
+ .data_offset = SYSCTL_FIELD_UINT_OFFSET(struct ipc_namespace,
+ msg_ctlmax),
+ .uint_limits = {
+ .min_value = SYSCTL_UINT_ZERO,
+ .max_value = &ipc_uint_max,
+ },
},
{
.procname = "msgmni",
- .data = &init_ipc_ns.msg_ctlmni,
- .maxlen = sizeof(init_ipc_ns.msg_ctlmni),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = &ipc_mni,
+ .type = SYSCTL_FIELD_UINT_MINMAX,
+ .data_offset = SYSCTL_FIELD_UINT_OFFSET(struct ipc_namespace,
+ msg_ctlmni),
+ .uint_limits = {
+ .min_value = SYSCTL_UINT_ZERO,
+ .max_value = &ipc_mni_max,
+ },
},
{
.procname = "auto_msgmni",
- .data = NULL,
- .maxlen = sizeof(int),
.mode = 0644,
+ .type = SYSCTL_FIELD_NO_DATA,
.proc_handler = proc_ipc_auto_msgmni,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_ONE,
+ .maxlen = sizeof(int),
},
{
- .procname = "msgmnb",
- .data = &init_ipc_ns.msg_ctlmnb,
- .maxlen = sizeof(init_ipc_ns.msg_ctlmnb),
+ .procname = "msgmnb",
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_INT_MAX,
+ .type = SYSCTL_FIELD_UINT_MINMAX,
+ .data_offset = SYSCTL_FIELD_UINT_OFFSET(struct ipc_namespace,
+ msg_ctlmnb),
+ .uint_limits = {
+ .min_value = SYSCTL_UINT_ZERO,
+ .max_value = &ipc_uint_max,
+ },
},
{
.procname = "sem",
- .data = &init_ipc_ns.sem_ctls,
- .maxlen = 4*sizeof(int),
.mode = 0644,
+ .type = SYSCTL_FIELD_INT,
.proc_handler = proc_ipc_sem_dointvec,
+ .maxlen = 4 * sizeof(int),
+ .data_offset = SYSCTL_FIELD_INT_OFFSET(struct ipc_namespace,
+ sem_ctls[0]),
},
#ifdef CONFIG_CHECKPOINT_RESTORE
{
.procname = "sem_next_id",
- .data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
- .maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
.mode = 0444,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_INT_MAX,
+ .type = SYSCTL_FIELD_INT_MINMAX,
+ .data_offset = SYSCTL_FIELD_INT_OFFSET(struct ipc_namespace,
+ ids[IPC_SEM_IDS].next_id),
+ .int_limits = {
+ .min_value = SYSCTL_ZERO,
+ .max_value = SYSCTL_INT_MAX,
+ },
},
{
.procname = "msg_next_id",
- .data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
- .maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
.mode = 0444,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_INT_MAX,
+ .type = SYSCTL_FIELD_INT_MINMAX,
+ .data_offset = SYSCTL_FIELD_INT_OFFSET(struct ipc_namespace,
+ ids[IPC_MSG_IDS].next_id),
+ .int_limits = {
+ .min_value = SYSCTL_ZERO,
+ .max_value = SYSCTL_INT_MAX,
+ },
},
{
.procname = "shm_next_id",
- .data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
- .maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
.mode = 0444,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_INT_MAX,
+ .type = SYSCTL_FIELD_INT_MINMAX,
+ .data_offset = SYSCTL_FIELD_INT_OFFSET(struct ipc_namespace,
+ ids[IPC_SHM_IDS].next_id),
+ .int_limits = {
+ .min_value = SYSCTL_ZERO,
+ .max_value = SYSCTL_INT_MAX,
+ },
},
#endif
};
@@ -244,57 +264,16 @@ static struct ctl_table_root set_root = {
bool setup_ipc_sysctls(struct ipc_namespace *ns)
{
- struct ctl_table *tbl;
+ struct sysctl_context ctx = {
+ .type = SYSCTL_CONTEXT_IPC_NS,
+ .object_size = sizeof(*ns),
+ .ns.ipc_ns = ns,
+ };
setup_sysctl_set(&ns->ipc_set, &set_root, set_is_seen);
-
- tbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL);
- if (tbl) {
- int i;
-
- for (i = 0; i < ARRAY_SIZE(ipc_sysctls); i++) {
- if (tbl[i].data == &init_ipc_ns.shm_ctlmax)
- tbl[i].data = &ns->shm_ctlmax;
-
- else if (tbl[i].data == &init_ipc_ns.shm_ctlall)
- tbl[i].data = &ns->shm_ctlall;
-
- else if (tbl[i].data == &init_ipc_ns.shm_ctlmni)
- tbl[i].data = &ns->shm_ctlmni;
-
- else if (tbl[i].data == &init_ipc_ns.shm_rmid_forced)
- tbl[i].data = &ns->shm_rmid_forced;
-
- else if (tbl[i].data == &init_ipc_ns.msg_ctlmax)
- tbl[i].data = &ns->msg_ctlmax;
-
- else if (tbl[i].data == &init_ipc_ns.msg_ctlmni)
- tbl[i].data = &ns->msg_ctlmni;
-
- else if (tbl[i].data == &init_ipc_ns.msg_ctlmnb)
- tbl[i].data = &ns->msg_ctlmnb;
-
- else if (tbl[i].data == &init_ipc_ns.sem_ctls)
- tbl[i].data = &ns->sem_ctls;
-#ifdef CONFIG_CHECKPOINT_RESTORE
- else if (tbl[i].data == &init_ipc_ns.ids[IPC_SEM_IDS].next_id)
- tbl[i].data = &ns->ids[IPC_SEM_IDS].next_id;
-
- else if (tbl[i].data == &init_ipc_ns.ids[IPC_MSG_IDS].next_id)
- tbl[i].data = &ns->ids[IPC_MSG_IDS].next_id;
-
- else if (tbl[i].data == &init_ipc_ns.ids[IPC_SHM_IDS].next_id)
- tbl[i].data = &ns->ids[IPC_SHM_IDS].next_id;
-#endif
- else
- tbl[i].data = NULL;
- }
-
- ns->ipc_sysctls = __register_sysctl_table(&ns->ipc_set, "kernel", tbl,
- ARRAY_SIZE(ipc_sysctls));
- }
+ ns->ipc_sysctls =
+ register_sysctl_fields(&ns->ipc_set, "kernel", ipc_sysctls, &ctx);
if (!ns->ipc_sysctls) {
- kfree(tbl);
retire_sysctl_set(&ns->ipc_set);
return false;
}
@@ -304,12 +283,8 @@ bool setup_ipc_sysctls(struct ipc_namespace *ns)
void retire_ipc_sysctls(struct ipc_namespace *ns)
{
- const struct ctl_table *tbl;
-
- tbl = ns->ipc_sysctls->ctl_table_arg;
unregister_sysctl_table(ns->ipc_sysctls);
retire_sysctl_set(&ns->ipc_set);
- kfree(tbl);
}
static int __init ipc_sysctl_init(void)
@@ -326,6 +301,7 @@ device_initcall(ipc_sysctl_init);
static int __init ipc_mni_extend(char *str)
{
ipc_mni = IPCMNI_EXTEND;
+ ipc_mni_max = IPCMNI_EXTEND;
ipc_mni_shift = IPCMNI_EXTEND_SHIFT;
ipc_min_cycle = IPCMNI_EXTEND_MIN_CYCLE;
pr_info("IPCMNI extended to %d.\n", ipc_mni);
--
2.55.0