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Subject[PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC()
Those functions that use NODEMASK_ALLOC() can't propogate errno
to users, but will fail silently.

Since all of them are called with cgroup_mutex held, here we use
a global nodemask_t variable.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/cpuset.c | 45 +++++++++++++++------------------------------
1 files changed, 15 insertions(+), 30 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 70c9ca2..cc414ac 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -79,6 +79,15 @@ int number_of_cpusets __read_mostly;
struct cgroup_subsys cpuset_subsys;
struct cpuset;

+/*
+ * In functions that can't propogate errno to users, to avoid declaring a
+ * nodemask_t variable, and avoid using NODEMASK_ALLOC that can return
+ * -ENOMEM, we use this global cpuset_mems.
+ *
+ * It should be used with cgroup_lock held.
+ */
+static nodemask_t cpuset_mems;
+
/* See "Frequency meter" comments, below. */

struct fmeter {
@@ -1015,17 +1024,11 @@ static void cpuset_change_nodemask(struct task_struct *p,
struct cpuset *cs;
int migrate;
const nodemask_t *oldmem = scan->data;
- NODEMASK_ALLOC(nodemask_t, newmems, GFP_KERNEL);
-
- if (!newmems)
- return;

cs = cgroup_cs(scan->cg);
- guarantee_online_mems(cs, newmems);
-
- cpuset_change_task_nodemask(p, newmems);
+ guarantee_online_mems(cs, &cpuset_mems);

- NODEMASK_FREE(newmems);
+ cpuset_change_task_nodemask(p, &cpuset_mems);

mm = get_task_mm(p);
if (!mm)
@@ -1096,13 +1099,10 @@ static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
const char *buf)
{
- NODEMASK_ALLOC(nodemask_t, oldmem, GFP_KERNEL);
+ nodemask_t *oldmem = &cpuset_mems;
int retval;
struct ptr_heap heap;

- if (!oldmem)
- return -ENOMEM;
-
/*
* top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
* it's read-only
@@ -1152,7 +1152,6 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,

heap_free(&heap);
done:
- NODEMASK_FREE(oldmem);
return retval;
}

@@ -1438,10 +1437,7 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
struct mm_struct *mm;
struct cpuset *cs = cgroup_cs(cont);
struct cpuset *oldcs = cgroup_cs(oldcont);
- NODEMASK_ALLOC(nodemask_t, to, GFP_KERNEL);
-
- if (to == NULL)
- goto alloc_fail;
+ nodemask_t *to = &cpuset_mems;

if (cs == &top_cpuset) {
cpumask_copy(cpus_attach, cpu_possible_mask);
@@ -1470,9 +1466,6 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
cpuset_migrate_mm(mm, &oldcs->mems_allowed, to);
mmput(mm);
}
-
-alloc_fail:
- NODEMASK_FREE(to);
}

/* The various types of files and directories in a cpuset file system */
@@ -2051,10 +2044,7 @@ static void scan_for_empty_cpusets(struct cpuset *root)
struct cpuset *cp; /* scans cpusets being updated */
struct cpuset *child; /* scans child cpusets of cp */
struct cgroup *cont;
- NODEMASK_ALLOC(nodemask_t, oldmems, GFP_KERNEL);
-
- if (oldmems == NULL)
- return;
+ nodemask_t *oldmems = &cpuset_mems;

list_add_tail((struct list_head *)&root->stack_list, &queue);

@@ -2090,7 +2080,6 @@ static void scan_for_empty_cpusets(struct cpuset *root)
update_tasks_nodemask(cp, oldmems, NULL);
}
}
- NODEMASK_FREE(oldmems);
}

/*
@@ -2132,10 +2121,7 @@ void cpuset_update_active_cpus(void)
static int cpuset_track_online_nodes(struct notifier_block *self,
unsigned long action, void *arg)
{
- NODEMASK_ALLOC(nodemask_t, oldmems, GFP_KERNEL);
-
- if (oldmems == NULL)
- return NOTIFY_DONE;
+ nodemask_t *oldmems = &cpuset_mems;

cgroup_lock();
switch (action) {
@@ -2158,7 +2144,6 @@ static int cpuset_track_online_nodes(struct notifier_block *self,
}
cgroup_unlock();

- NODEMASK_FREE(oldmems);
return NOTIFY_OK;
}
#endif
--
1.7.3.1

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