Subject: [merged] kthread-make-kthread_create-killable.patch removed from -mm tree
To: penguin-kernel@xxxxxxxxxxxxxxxxxxx,oleg@xxxxxxxxxx,rientjes@xxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 13 Nov 2013 12:36:56 -0800
The patch titled
Subject: kthread: make kthread_create() killable
has been removed from the -mm tree. Its filename was
kthread-make-kthread_create-killable.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: kthread: make kthread_create() killable
Any user process callers of wait_for_completion() except global init
process might be chosen by the OOM killer while waiting for completion()
call by some other process which does memory allocation. See
CVE-2012-4398 "kernel: request_module() OOM local DoS" can happen.
When such users are chosen by the OOM killer when they are waiting for
completion() in TASK_UNINTERRUPTIBLE, the system will be kept stressed due
to memory starvation because the OOM killer cannot kill such users.
kthread_create() is one of such users and this patch fixes the problem for
kthreadd by making kthread_create() killable - the same approach used for
fixing CVE-2012-4398.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kthread.c | 73 +++++++++++++++++++++++++++++++++------------
1 file changed, 55 insertions(+), 18 deletions(-)
diff -puN kernel/kthread.c~kthread-make-kthread_create-killable kernel/kthread.c
--- a/kernel/kthread.c~kthread-make-kthread_create-killable
+++ a/kernel/kthread.c
@@ -33,7 +33,7 @@ struct kthread_create_info
/* Result passed back to kthread_create() from kthreadd. */
struct task_struct *result;
- struct completion done;
+ struct completion *done;
struct list_head list;
};
@@ -178,6 +178,7 @@ static int kthread(void *_create)
struct kthread_create_info *create = _create;
int (*threadfn)(void *data) = create->threadfn;
void *data = create->data;
+ struct completion *done;
struct kthread self;
int ret;
@@ -187,10 +188,16 @@ static int kthread(void *_create)
init_completion(&self.parked);
current->vfork_done = &self.exited;
+ /* If user was SIGKILLed, I release the structure. */
+ done = xchg(&create->done, NULL);
+ if (!done) {
+ kfree(create);
+ do_exit(-EINTR);
+ }
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_UNINTERRUPTIBLE);
create->result = current;
- complete(&create->done);
+ complete(done);
schedule();
ret = -EINTR;
@@ -223,8 +230,15 @@ static void create_kthread(struct kthrea
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
if (pid < 0) {
+ /* If user was SIGKILLed, I release the structure. */
+ struct completion *done = xchg(&create->done, NULL);
+
+ if (!done) {
+ kfree(create);
+ return;
+ }
create->result = ERR_PTR(pid);
- complete(&create->done);
+ complete(done);
}
}
@@ -255,36 +269,59 @@ struct task_struct *kthread_create_on_no
const char namefmt[],
...)
{
- struct kthread_create_info create;
-
- create.threadfn = threadfn;
- create.data = data;
- create.node = node;
- init_completion(&create.done);
+ DECLARE_COMPLETION_ONSTACK(done);
+ struct task_struct *task;
+ struct kthread_create_info *create = kmalloc(sizeof(*create),
+ GFP_KERNEL);
+
+ if (!create)
+ return ERR_PTR(-ENOMEM);
+ create->threadfn = threadfn;
+ create->data = data;
+ create->node = node;
+ create->done = &done;
spin_lock(&kthread_create_lock);
- list_add_tail(&create.list, &kthread_create_list);
+ list_add_tail(&create->list, &kthread_create_list);
spin_unlock(&kthread_create_lock);
wake_up_process(kthreadd_task);
- wait_for_completion(&create.done);
-
- if (!IS_ERR(create.result)) {
+ /*
+ * Wait for completion in killable state, for I might be chosen by
+ * the OOM killer while kthreadd is trying to allocate memory for
+ * new kernel thread.
+ */
+ if (unlikely(wait_for_completion_killable(&done))) {
+ /*
+ * If I was SIGKILLed before kthreadd (or new kernel thread)
+ * calls complete(), leave the cleanup of this structure to
+ * that thread.
+ */
+ if (xchg(&create->done, NULL))
+ return ERR_PTR(-ENOMEM);
+ /*
+ * kthreadd (or new kernel thread) will call complete()
+ * shortly.
+ */
+ wait_for_completion(&done);
+ }
+ task = create->result;
+ if (!IS_ERR(task)) {
static const struct sched_param param = { .sched_priority = 0 };
va_list args;
va_start(args, namefmt);
- vsnprintf(create.result->comm, sizeof(create.result->comm),
- namefmt, args);
+ vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
va_end(args);
/*
* root may have changed our (kthreadd's) priority or CPU mask.
* The kernel thread should not inherit these properties.
*/
- sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
- set_cpus_allowed_ptr(create.result, cpu_all_mask);
+ sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
+ set_cpus_allowed_ptr(task, cpu_all_mask);
}
- return create.result;
+ kfree(create);
+ return task;
}
EXPORT_SYMBOL(kthread_create_on_node);
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
seq_file-introduce-seq_setwidth-and-seq_pad.patch
seq_file-remove-%n-usage-from-seq_file-users.patch
vsprintf-ignore-%n-again.patch
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