[PATCH RFC 3/4] ipc: Use sysctl context to register ipc namespaces
From: Joel Granados
Date: Thu Sep 24 2026 - 10:48:42 EST
Replace the ipc_sysctls array copy with a sysctl context kept in the
ctl_table_header. Flag each entry with CTL_TABLE_F_CTX_DATA to overlay
the ctl_table entry before calling the proc_handler. auto_msgmni is left
unflagged. Its NULL ->data is handled by its custom proc_handler.
proc_ipc_{dointvec_minmax_orphans,sem_dointvec} and ipc_permissions are
handed a resolved entry, so they keep seeing the namespace entry.
Signed-off-by: Joel Granados <joel.granados@xxxxxxxxxx>
---
ipc/ipc_sysctl.c | 68 +++++++++++++-------------------------------------------
1 file changed, 16 insertions(+), 52 deletions(-)
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index d038d944257f60b3a35b72492c73c41774a73da4..5d73487bb81c027da1ec2b1fa18dfde8242a223f 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"
@@ -79,6 +78,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.shm_ctlmax,
.maxlen = sizeof(init_ipc_ns.shm_ctlmax),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_doulongvec_minmax,
},
{
@@ -86,6 +86,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.shm_ctlall,
.maxlen = sizeof(init_ipc_ns.shm_ctlall),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_doulongvec_minmax,
},
{
@@ -93,6 +94,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.shm_ctlmni,
.maxlen = sizeof(init_ipc_ns.shm_ctlmni),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = &ipc_mni,
@@ -102,6 +104,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.shm_rmid_forced,
.maxlen = sizeof(init_ipc_ns.shm_rmid_forced),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_ipc_dointvec_minmax_orphans,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
@@ -111,6 +114,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.msg_ctlmax,
.maxlen = sizeof(init_ipc_ns.msg_ctlmax),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
@@ -120,6 +124,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.msg_ctlmni,
.maxlen = sizeof(init_ipc_ns.msg_ctlmni),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = &ipc_mni,
@@ -138,6 +143,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.msg_ctlmnb,
.maxlen = sizeof(init_ipc_ns.msg_ctlmnb),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
@@ -147,6 +153,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.sem_ctls,
.maxlen = 4*sizeof(int),
.mode = 0644,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_ipc_sem_dointvec,
},
#ifdef CONFIG_CHECKPOINT_RESTORE
@@ -155,6 +162,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
.maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
.mode = 0444,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
@@ -164,6 +172,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
.maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
.mode = 0444,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
@@ -173,6 +182,7 @@ static const struct ctl_table ipc_sysctls[] = {
.data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
.maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
.mode = 0444,
+ .flags = CTL_TABLE_F_CTX_DATA,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
@@ -244,57 +254,15 @@ static struct ctl_table_root set_root = {
bool setup_ipc_sysctls(struct ipc_namespace *ns)
{
- struct ctl_table *tbl;
+ struct sysctl_context ctx = SYSCTL_CTX(ns, &init_ipc_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_table_ctx(&ns->ipc_set, "kernel",
+ ipc_sysctls,
+ ARRAY_SIZE(ipc_sysctls),
+ &ctx);
if (!ns->ipc_sysctls) {
- kfree(tbl);
retire_sysctl_set(&ns->ipc_set);
return false;
}
@@ -304,12 +272,8 @@ 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)
--
2.50.1