It happens that the new IPC id sequence number inrement mode can be
useful to reduce the chance of IPC id reuse even if the ipcmni_extend
boot command line parameter isn't specified. So a new ipcid_mode sysctl
parameter is added to control the sequence number generation mode -
legacy and delete modes.
In the legacy mode, the sequence number is incremented every time a new
ID is generated. In the delete mode, the number is incremented only if
one or more IDs have been previously deleted. The default is legacy for
non-ipcmni_extend and delete for ipcmni_extend. This new ipcid_mode
parameter is specific to each of the IPC namespaces.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
Documentation/sysctl/kernel.txt | 17 +++++++++++++++++
include/linux/ipc_namespace.h | 12 ++++++++++++
ipc/ipc_sysctl.c | 10 ++++++++++
ipc/msg.c | 3 ++-
ipc/namespace.c | 2 ++
ipc/sem.c | 3 ++-
ipc/shm.c | 3 ++-
ipc/util.c | 10 ++++++----
ipc/util.h | 3 ++-
9 files changed, 55 insertions(+), 8 deletions(-)
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 37a6795..91bada1 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -41,6 +41,7 @@ show up in /proc/sys/kernel:
- hung_task_check_interval_secs
- hung_task_warnings
- hyperv_record_panic_msg
+- ipcid_mode
- kexec_load_disabled
- kptr_restrict
- l2cr [ PPC only ]
@@ -398,6 +399,22 @@ Controls whether the panic kmsg data should be reported to Hyper-V.
==============================================================
+ipcid_mode:
+
+Controls how the IPC ids returned by msgget(), semget() and shmget()
+are being generated.
+
+0: legacy mode
+1: delete mode
+
+There are two components in an IPC id - an integer identifier and a
+sequence number. In the legacy mode, the sequence number is incremented
+every time a new id is generated. In the delete mode, the sequence number
+is only incremented if one or more ids have been previously deleted. The
+delete mode reduces the chance that a given id will be reused again.
+
+==============================================================
+
kexec_load_disabled:
A toggle indicating if the kexec_load syscall has been disabled. This
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 7d5f553..79d9d50 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -26,6 +26,15 @@ struct ipc_ids {
struct rhashtable key_ht;
};
+/*
+ * IPC id generation mode for controlling how the IPC id returned by
+ * {msg,sem,shm}get() is being generated.
+ */
+enum ipc_id_mode {
+ ipc_id_legacy, /* Sequence # incremented on every allocation */
+ ipc_id_delete, /* Sequence # incremented only if an ID was deleted */
+};
+
struct ipc_namespace {
refcount_t count;
struct ipc_ids ids[3];
@@ -39,6 +48,9 @@ struct ipc_namespace {
atomic_t msg_bytes;
atomic_t msg_hdrs;
+ /* IPC id generation mode */
+ unsigned int ipcid_mode;
+
size_t shm_ctlmax;
size_t shm_ctlall;
unsigned long shm_tot;
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index d9ac6ca..4c30e62 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -200,6 +200,15 @@ static int proc_ipc_sem_dointvec(struct ctl_table *table, int write,
.mode = 0644,
.proc_handler = proc_ipc_sem_dointvec,
},
+ {
+ .procname = "ipcid_mode",
+ .data = &init_ipc_ns.ipcid_mode,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_ipc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
#ifdef CONFIG_CHECKPOINT_RESTORE
{
.procname = "sem_next_id",
@@ -254,6 +263,7 @@ static int __init ipc_mni_extend(char *str)
ipc_mni = IPCMNI_EXTEND;
ipc_mni_shift = IPCMNI_EXTEND_SHIFT;
ipc_mni_extended = true;
+ init_ipc_ns.ipcid_mode = ipc_id_delete;
pr_info("IPCMNI extended to %d.\n", ipc_mni);
return 0;
}
diff --git a/ipc/msg.c b/ipc/msg.c
index 0833c64..b401ba2 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -161,7 +161,8 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
INIT_LIST_HEAD(&msq->q_senders);
/* ipc_addid() locks msq upon success. */
- retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
+ retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni,
+ ns->ipcid_mode);
if (retval < 0) {
ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
return retval;
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 2160779..8b62cbd0 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -55,6 +55,8 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
ns->user_ns = get_user_ns(user_ns);
ns->ucounts = ucounts;
+ ns->ipcid_mode = ipc_mni_extended ? ipc_id_delete : ipc_id_legacy;
+
err = mq_init_ns(ns);
if (err)
goto fail_put;
diff --git a/ipc/sem.c b/ipc/sem.c
index 745dc61..51af634 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -553,7 +553,8 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
sma->sem_ctime = ktime_get_real_seconds();
/* ipc_addid() locks sma upon success. */
- retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
+ retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni,
+ ns->ipcid_mode);
if (retval < 0) {
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
return retval;
diff --git a/ipc/shm.c b/ipc/shm.c
index 0842411..182ae4c 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -676,7 +676,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
shp->shm_creator = current;
/* ipc_addid() locks shp upon success. */
- error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
+ error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni,
+ ns->ipcid_mode);
if (error < 0)
goto no_id;
diff --git a/ipc/util.c b/ipc/util.c
index 6ae0007..04c8e31 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -195,7 +195,8 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
* The caller must own kern_ipc_perm.lock.of the new object.
* On error, the function returns a (negative) error code.
*/
-static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
+static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new,
+ int idmode)
{
int idx, next_id = -1;
@@ -222,7 +223,7 @@ static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
*/
if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
- if (!ipc_mni_extended || ids->deleted) {
+ if (idmode == ipc_id_legacy || ids->deleted) {
ids->seq++;
if (ids->seq > IPCID_SEQ_MAX)
ids->seq = 0;
@@ -255,7 +256,8 @@ static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
*
* Called with writer ipc_ids.rwsem held.
*/
-int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
+int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit,
+ int idmode)
{
kuid_t euid;
kgid_t egid;
@@ -282,7 +284,7 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
new->deleted = false;
- idx = ipc_idr_alloc(ids, new);
+ idx = ipc_idr_alloc(ids, new, idmode);
idr_preload_end();
if (idx >= 0 && new->key != IPC_PRIVATE) {
diff --git a/ipc/util.h b/ipc/util.h
index 1f19729..c8f2d0ed 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -129,7 +129,8 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
#define IPCID_SEQ_MAX (INT_MAX >> IPCMNI_SEQ_SHIFT)
/* must be called with ids->rwsem acquired for writing */
-int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
+int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit,
+ int idmode);
/* must be called with both locks acquired. */
void ipc_rmid(struct ipc_ids *, struct kern_ipc_perm *);
--
1.8.3.1
