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Commit b2c903b8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

exec: simplify the new ->sighand allocation 



de_thread() pre-allocates newsighand to make sure that exec() can't fail after
killing all sub-threads. Imho, this buys nothing, but complicates the code:

	- this is (mostly) needed to handle CLONE_SIGHAND without CLONE_THREAD
	  tasks, this is very unlikely (if ever used) case

	- unless we already have some serious problems, GFP_KERNEL allocation
	  should not fail

	- ENOMEM still can happen after de_thread(), ->sighand is not the last
	  object we have to allocate

Change the code to allocate the new ->sighand on demand.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0840a90d

fs/exec.c

+9 −15
Original line number Diff line number Diff line
@@ -747,7 +747,7 @@ static int exec_mmap(struct mm_struct *mm) 
static int de_thread(struct task_struct *tsk)

{

	struct signal_struct *sig = tsk->signal;

	struct sighand_struct *newsighand, *oldsighand = tsk->sighand;

	struct sighand_struct *oldsighand = tsk->sighand;

	spinlock_t *lock = &oldsighand->siglock;

	struct task_struct *leader = NULL;

	int count;
@@ -761,10 +761,6 @@ static int de_thread(struct task_struct *tsk) 
		return 0;

	}



	newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);

	if (!newsighand)

		return -ENOMEM;



	if (thread_group_empty(tsk))

		goto no_thread_group;
@@ -781,7 +777,6 @@ static int de_thread(struct task_struct *tsk) 
		 */

		spin_unlock_irq(lock);

		read_unlock(&tasklist_lock);

		kmem_cache_free(sighand_cachep, newsighand);

		return -EAGAIN;

	}
@@ -899,17 +894,16 @@ no_thread_group: 
	if (leader)

		release_task(leader);



	if (atomic_read(&oldsighand->count) == 1) {

	if (atomic_read(&oldsighand->count) != 1) {

		struct sighand_struct *newsighand;

		/*

		 * Now that we nuked the rest of the thread group,

		 * it turns out we are not sharing sighand any more either.

		 * So we can just keep it.

		 */

		kmem_cache_free(sighand_cachep, newsighand);

	} else {

		/*

		 * Move our state over to newsighand and switch it in.

		 * This ->sighand is shared with the CLONE_SIGHAND

		 * but not CLONE_THREAD task, switch to the new one.

		 */

		newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);

		if (!newsighand)

			return -ENOMEM;



		atomic_set(&newsighand->count, 1);

		memcpy(newsighand->action, oldsighand->action,

		       sizeof(newsighand->action));