The semaphore undo list is a set of adjustments to be made to semaphores
held by a task on exit. Right now, we do not checkpoint or restore this
list which could cause undesirable behavior by a restarted process on exit.
Signed-off-by: Dan Smith <danms@xxxxxxxxxx>
---
include/linux/checkpoint.h | 5 +
include/linux/checkpoint_hdr.h | 18 +++
ipc/sem.c | 332 +++++++++++++++++++++++++++++++++++++++-
kernel/checkpoint/process.c | 16 ++
4 files changed, 365 insertions(+), 6 deletions(-)
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 0437de2..285689a 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -275,6 +275,11 @@ extern int ckpt_collect_fs(struct ckpt_ctx *ctx, struct task_struct *t);
extern int checkpoint_obj_fs(struct ckpt_ctx *ctx, struct task_struct *t);
extern int restore_obj_fs(struct ckpt_ctx *ctx, int fs_objref);
+/* per-task semaphore undo */
+int checkpoint_obj_sem_undo(struct ckpt_ctx *ctx, struct task_struct *t);
+int restore_obj_sem_undo(struct ckpt_ctx *ctx, int sem_undo_objref);
+int ckpt_collect_sem_undo(struct ckpt_ctx *ctx, struct task_struct *t);
+
/* memory */
extern void ckpt_pgarr_free(struct ckpt_ctx *ctx);
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index f4f9577..b48fa37 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -167,6 +167,10 @@ enum {
#define CKPT_HDR_IPC_MSG_MSG CKPT_HDR_IPC_MSG_MSG
CKPT_HDR_IPC_SEM,
#define CKPT_HDR_IPC_SEM CKPT_HDR_IPC_SEM
+ CKPT_HDR_TASK_SEM_UNDO_LIST,
+#define CKPT_HDR_TASK_SEM_UNDO_LIST CKPT_HDR_TASK_SEM_UNDO_LIST
+ CKPT_HDR_TASK_SEM_UNDO,
+#define CKPT_HDR_TASK_SEM_UNDO CKPT_HDR_TASK_SEM_UNDO
CKPT_HDR_SIGHAND = 601,
#define CKPT_HDR_SIGHAND CKPT_HDR_SIGHAND
@@ -273,6 +277,8 @@ enum obj_type {
#define CKPT_OBJ_NET_NS CKPT_OBJ_NET_NS
CKPT_OBJ_NETDEV,
#define CKPT_OBJ_NETDEV CKPT_OBJ_NETDEV
+ CKPT_OBJ_SEM_UNDO,
+#define CKPT_OBJ_SEM_UNDO CKPT_OBJ_SEM_UNDO
CKPT_OBJ_MAX
#define CKPT_OBJ_MAX CKPT_OBJ_MAX
};
@@ -461,6 +467,17 @@ struct ckpt_hdr_ns {
__s32 net_objref;
} __attribute__((aligned(8)));
+struct ckpt_hdr_task_sem_undo_list {
+ struct ckpt_hdr h;
+ __u32 count;
+};
+
+struct ckpt_hdr_task_sem_undo {
+ struct ckpt_hdr h;
+ __u32 semid;
+ __u32 semadj_count;
+};
+
/* cannot include <linux/tty.h> from userspace, so define: */
#define CKPT_NEW_UTS_LEN 64
#ifdef __KERNEL__
@@ -487,6 +504,7 @@ struct ckpt_hdr_task_objs {
__s32 files_objref;
__s32 mm_objref;
__s32 fs_objref;
+ __s32 sem_undo_objref;
__s32 sighand_objref;
__s32 signal_objref;
} __attribute__((aligned(8)));
diff --git a/ipc/sem.c b/ipc/sem.c
index 37da85e..fdad527 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -132,12 +132,49 @@ void sem_exit_ns(struct ipc_namespace *ns)
}
#endif
+static int obj_sem_undo_grab(void *ptr)
+{
+ struct sem_undo_list *ulp = ptr;
+
+ atomic_inc(&ulp->refcnt);
+ return 0;
+}
+
+static void obj_sem_undo_drop(void *ptr, int lastref)
+{
+ struct sem_undo_list *ulp = ptr;
+
+ atomic_dec(&ulp->refcnt);
+}
+
+static int obj_sem_undo_users(void *ptr)
+{
+ struct sem_undo_list *ulp = ptr;
+
+ return atomic_read(&ulp->refcnt);
+}
+
+static void *restore_sem_undo(struct ckpt_ctx *ctx);
+static int checkpoint_sem_undo(struct ckpt_ctx *ctx, void *ptr);
+
+static const struct ckpt_obj_ops ckpt_obj_sem_undo_ops = {
+ .obj_name = "IPC_SEM_UNDO",
+ .obj_type = CKPT_OBJ_SEM_UNDO,
+ .ref_drop = obj_sem_undo_drop,
+ .ref_grab = obj_sem_undo_grab,
+ .ref_users = obj_sem_undo_users,
+ .checkpoint = checkpoint_sem_undo,
+ .restore = restore_sem_undo,
+};
+
void __init sem_init (void)
{
sem_init_ns(&init_ipc_ns);
ipc_init_proc_interface("sysvipc/sem",
" key semid perms nsems uid gid cuid cgid otime ctime\n",
IPC_SEM_IDS, sysvipc_sem_proc_show);
+ register_checkpoint_obj(&ckpt_obj_sem_undo_ops);
+
}
/*
@@ -983,6 +1020,20 @@ asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
SYSCALL_ALIAS(sys_semctl, SyS_semctl);
#endif
+static struct sem_undo_list *alloc_undo_list(void)
+{
+ struct sem_undo_list *undo_list;
+
+ undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
+ if (undo_list == NULL)
+ return NULL;
+ spin_lock_init(&undo_list->lock);
+ atomic_set(&undo_list->refcnt, 1);
+ INIT_LIST_HEAD(&undo_list->list_proc);
+
+ return undo_list;
+}
+
/* If the task doesn't already have a undo_list, then allocate one
* here. We guarantee there is only one thread using this undo list,
* and current is THE ONE
@@ -1000,13 +1051,9 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
undo_list = current->sysvsem.undo_list;
if (!undo_list) {
- undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
- if (undo_list == NULL)
+ undo_list = alloc_undo_list();
+ if (!undo_list)
return -ENOMEM;
- spin_lock_init(&undo_list->lock);
- atomic_set(&undo_list->refcnt, 1);
- INIT_LIST_HEAD(&undo_list->list_proc);
-
current->sysvsem.undo_list = undo_list;
}
*undo_listp = undo_list;
@@ -1458,3 +1505,276 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
sma->sem_ctime);
}
#endif
+
+static int __get_task_semids(struct sem_undo_list *ulp, int *semids, int max)
+{
+ int count = 0;
+ struct sem_undo *un;
+
+ if (!ulp)
+ return 0;
+
+ spin_lock(&ulp->lock);
+ list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
+ if (count >= max) {
+ count = -E2BIG;
+ break;
+ }
+ semids[count++] = un->semid;
+ }
+ spin_unlock(&ulp->lock);
+
+ return count;
+}
+
+static int get_task_semids(struct sem_undo_list *ulp, int **semid_listp)
+{
+ int ret;
+ int max = 32;
+ int *semid_list = NULL;
+ retry:
+ *semid_listp = krealloc(semid_list, max * sizeof(int), GFP_KERNEL);
+ if (!*semid_listp) {
+ kfree(semid_list);
+ return -ENOMEM;
+ }
+ semid_list = *semid_listp;
+
+ ret = __get_task_semids(ulp, semid_list, max);
+ if (ret == -E2BIG) {
+ max *= 2;
+ goto retry;
+ } else if (ret < 0) {
+ kfree(semid_list);
+ *semid_listp = NULL;
+ }
+
+ return ret;
+}
+
+int checkpoint_sem_undo_adj(struct ckpt_ctx *ctx, struct sem_undo *un)
+{
+ int nsems;
+ int ret;
+ short *semadj = NULL;
+ struct sem_array *sma;
+ struct ckpt_hdr_task_sem_undo *h = NULL;
+
+ sma = sem_lock(ctx->root_nsproxy->ipc_ns, un->semid);
+ if (IS_ERR(sma)) {
+ ckpt_debug("unable to lock semid %i (wrong ns?)\n", un->semid);
+ return PTR_ERR(sma);
+ }
+
+ nsems = sma->sem_nsems;
+ sem_getref_and_unlock(sma);
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_TASK_SEM_UNDO);
+ if (!h)
+ goto putref_abort;
+
+ semadj = kzalloc(nsems * sizeof(short), GFP_KERNEL);
+ if (!semadj)
+ goto putref_abort;
+
+ sem_lock_and_putref(sma);
+
+ h->semid = un->semid;
+ h->semadj_count = nsems;
+ memcpy(semadj, un->semadj, h->semadj_count * sizeof(short));
+
+ sem_unlock(sma);
+
+ ret = ckpt_write_obj(ctx, (struct ckpt_hdr *)h);
+ if (ret == 0)
+ ret = ckpt_write_buffer(ctx, semadj, nsems * sizeof(short));
+
+ kfree(semadj);
+
+ return ret;
+
+ putref_abort:
+ sem_putref(sma);
+ ckpt_hdr_put(ctx, h);
+
+ return -ENOMEM;
+}
+
+int write_sem_undo_list(struct ckpt_ctx *ctx, struct sem_undo_list *ulp,
+ int count, int *semids)
+{
+ int i;
+ int ret;
+
+ for (i = 0; i < count; i++) {
+ struct sem_undo *un;
+
+ spin_lock(&ulp->lock);
+ un = lookup_undo(ulp, semids[i]);
+ spin_unlock(&ulp->lock);
+
+ if (!un) {
+ ckpt_debug("unable to lookup semid %i\n", semids[i]);
+ return -EINVAL;
+ }
+
+ ret = checkpoint_sem_undo_adj(ctx, un);
+ ckpt_debug("checkpoint_sem_undo: %i\n", ret);
+ if (ret < 0)
+ return ret;
+ }
+
+ return 0;
+}
+
+static int checkpoint_sem_undo(struct ckpt_ctx *ctx, void *ptr)
+{
+ int ret;
+ int *semids = NULL;
+ struct sem_undo_list *ulp = ptr;
+ struct ckpt_hdr_task_sem_undo_list *h;
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_TASK_SEM_UNDO_LIST);
+ if (!h)
+ return -ENOMEM;
+
+ ret = get_task_semids(ulp, &semids);
+ if (ret < 0)
+ goto out;
+ h->count = ret;
+
+ ret = ckpt_write_obj(ctx, (struct ckpt_hdr *)h);
+ if (ret < 0)
+ goto out;
+
+ ret = write_sem_undo_list(ctx, ulp, h->count, semids);
+ out:
+ ckpt_hdr_put(ctx, h);
+ kfree(semids);
+
+ return ret;
+}
+
+int checkpoint_obj_sem_undo(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct sem_undo_list *ulp;
+ int sem_undo_objref = 0;
+
+ ulp = t->sysvsem.undo_list;
+ if (ulp)
+ sem_undo_objref = checkpoint_obj(ctx, ulp, CKPT_OBJ_SEM_UNDO);
+
+ return sem_undo_objref;
+}
+
+/* Count the number of sems for the given sem_undo->semid */
+static int sem_undo_nsems(struct sem_undo *un, struct ipc_namespace *ns)
+{
+ struct sem_array *sma;
+ int nsems;
+
+ sma = sem_lock(ns, un->semid);
+ if (IS_ERR(sma))
+ return PTR_ERR(sma);
+
+ nsems = sma->sem_nsems;
+ sem_unlock(sma);
+
+ return nsems;
+}
+
+static int restore_task_sem_undo_adj(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_task_sem_undo *h;
+ int len;
+ int ret = -ENOMEM;
+ struct sem_undo *un;
+ int nsems;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_TASK_SEM_UNDO);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ un = find_alloc_undo(current->nsproxy->ipc_ns, h->semid);
+ if (IS_ERR(un)) {
+ ret = PTR_ERR(un);
+ ckpt_debug("unable to find semid %i\n", h->semid);
+ goto out_nolock;
+ }
+
+ nsems = sem_undo_nsems(un, current->nsproxy->ipc_ns);
+ if (nsems != h->semadj_count) {
+ ckpt_err(ctx, -EINVAL,
+ "semid %i has nmsems=%i but %i undo adjustments\n",
+ h->semid, nsems, h->semadj_count);
+ goto out;
+ }
+
+ len = sizeof(short) * h->semadj_count;
+ ret = _ckpt_read_buffer(ctx, un->semadj, len);
+ if (ret < 0)
+ goto out;
+
+ ckpt_debug("semid %i restored with %i adjustments\n",
+ h->semid, h->semadj_count);
+ out:
+ rcu_read_unlock(); /* was taken by find_alloc_undo() */
+ out_nolock:
+ ckpt_hdr_put(ctx, h);
+
+ return ret;
+}
+
+static void *restore_sem_undo(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_task_sem_undo_list *h;
+ struct sem_undo_list *ulp = NULL;
+ int i;
+ int ret = 0;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_TASK_SEM_UNDO_LIST);
+ if (IS_ERR(h))
+ return ERR_PTR(PTR_ERR(h));
+
+ ulp = alloc_undo_list();
+ if (!ulp) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0; i < h->count; i++) {
+ ret = restore_task_sem_undo_adj(ctx);
+ if (ret < 0)
+ goto out;
+ }
+ out:
+ ckpt_hdr_put(ctx, h);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ else
+ return ulp;
+}
+
+int restore_obj_sem_undo(struct ckpt_ctx *ctx, int sem_undo_objref)
+{
+ struct sem_undo_list *ulp;
+
+ if (!sem_undo_objref)
+ return 0; /* Task had no undo list */
+
+ ulp = ckpt_obj_try_fetch(ctx, sem_undo_objref, CKPT_OBJ_SEM_UNDO);
+ if (IS_ERR(ulp))
+ return PTR_ERR(ulp);
+
+ return 0;
+}
+
+int ckpt_collect_sem_undo(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct sem_undo_list *ulp = t->sysvsem.undo_list;
+
+ if (ulp)
+ return ckpt_obj_collect(ctx, ulp, CKPT_OBJ_SEM_UNDO);
+ else
+ return 0;
+}
diff --git a/kernel/checkpoint/process.c b/kernel/checkpoint/process.c
index 936675a..2d50ac9 100644
--- a/kernel/checkpoint/process.c
+++ b/kernel/checkpoint/process.c
@@ -236,6 +236,7 @@ static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
int files_objref;
int mm_objref;
int fs_objref;
+ int sem_undo_objref;
int sighand_objref;
int signal_objref;
int first, ret;
@@ -283,6 +284,12 @@ static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
return fs_objref;
}
+ sem_undo_objref = checkpoint_obj_sem_undo(ctx, t);
+ if (sem_undo_objref < 0) {
+ ckpt_err(ctx, sem_undo_objref, "%(T)process sem_undo\n");
+ return sem_undo_objref;
+ }
+
sighand_objref = checkpoint_obj_sighand(ctx, t);
ckpt_debug("sighand: objref %d\n", sighand_objref);
if (sighand_objref < 0) {
@@ -311,6 +318,7 @@ static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
h->files_objref = files_objref;
h->mm_objref = mm_objref;
h->fs_objref = fs_objref;
+ h->sem_undo_objref = sem_undo_objref;
h->sighand_objref = sighand_objref;
h->signal_objref = signal_objref;
ret = ckpt_write_obj(ctx, &h->h);
@@ -492,6 +500,9 @@ int ckpt_collect_task(struct ckpt_ctx *ctx, struct task_struct *t)
ret = ckpt_collect_fs(ctx, t);
if (ret < 0)
return ret;
+ ret = ckpt_collect_sem_undo(ctx, t);
+ if (ret < 0)
+ return ret;
ret = ckpt_collect_sighand(ctx, t);
return ret;
@@ -679,6 +690,11 @@ static int restore_task_objs(struct ckpt_ctx *ctx)
if (ret < 0)
return ret;
+ ret = restore_obj_sem_undo(ctx, h->sem_undo_objref);
+ ckpt_debug("sem_undo: ret %d\n", ret);
+ if (ret < 0)
+ return ret;
+
ret = restore_obj_sighand(ctx, h->sighand_objref);
ckpt_debug("sighand: ret %d (%p)\n", ret, current->sighand);
if (ret < 0)
--
1.7.1.1
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