Commit 7865aba3 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
Browse files

fork: Don't assign the stack pointer in dup_task_struct() 



All four versions of alloc_thread_stack_node() assign now
task_struct::stack in case the allocation was successful.

Let alloc_thread_stack_node() return an error code instead of the stack
pointer and remove the stack assignment in dup_task_struct().

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20220217102406.3697941-5-bigeasy@linutronix.de
parent 2bb0529c

kernel/fork.c

+16 −31
Original line number Diff line number Diff line
@@ -211,7 +211,7 @@ static int free_vm_stack_cache(unsigned int cpu) 
	return 0;

}



static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)

static int alloc_thread_stack_node(struct task_struct *tsk, int node)

{

	void *stack;

	int i;
@@ -232,7 +232,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 


		tsk->stack_vm_area = s;

		tsk->stack = s->addr;

		return s->addr;

		return 0;

	}



	/*
@@ -245,17 +245,16 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) 
				     THREADINFO_GFP & ~__GFP_ACCOUNT,

				     PAGE_KERNEL,

				     0, node, __builtin_return_address(0));



	if (!stack)

		return -ENOMEM;

	/*

	 * We can't call find_vm_area() in interrupt context, and

	 * free_thread_stack() can be called in interrupt context,

	 * so cache the vm_struct.

	 */

	if (stack) {

	tsk->stack_vm_area = find_vm_area(stack);

	tsk->stack = stack;

	}

	return stack;

	return 0;

}



static void free_thread_stack(struct task_struct *tsk)
@@ -282,16 +281,16 @@ static void free_thread_stack(struct task_struct *tsk) 


#  else /* !CONFIG_VMAP_STACK */



static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)

static int alloc_thread_stack_node(struct task_struct *tsk, int node)

{

	struct page *page = alloc_pages_node(node, THREADINFO_GFP,

					     THREAD_SIZE_ORDER);



	if (likely(page)) {

		tsk->stack = kasan_reset_tag(page_address(page));

		return tsk->stack;

		return 0;

	}

	return NULL;

	return -ENOMEM;

}



static void free_thread_stack(struct task_struct *tsk)
@@ -305,14 +304,13 @@ static void free_thread_stack(struct task_struct *tsk) 


static struct kmem_cache *thread_stack_cache;



static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,

						  int node)

static int alloc_thread_stack_node(struct task_struct *tsk, int node)

{

	unsigned long *stack;

	stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);

	stack = kasan_reset_tag(stack);

	tsk->stack = stack;

	return stack;

	return stack ? 0 : -ENOMEM;

}



static void free_thread_stack(struct task_struct *tsk)
@@ -332,13 +330,13 @@ void thread_stack_cache_init(void) 
# endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */

#else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */



static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)

static int alloc_thread_stack_node(struct task_struct *tsk, int node)

{

	unsigned long *stack;



	stack = arch_alloc_thread_stack_node(tsk, node);

	tsk->stack = stack;

	return stack;

	return stack ? 0 : -ENOMEM;

}



static void free_thread_stack(struct task_struct *tsk)
@@ -895,8 +893,6 @@ void set_task_stack_end_magic(struct task_struct *tsk) 
static struct task_struct *dup_task_struct(struct task_struct *orig, int node)

{

	struct task_struct *tsk;

	unsigned long *stack;

	struct vm_struct *stack_vm_area __maybe_unused;

	int err;



	if (node == NUMA_NO_NODE)
@@ -909,24 +905,13 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 
	if (err)

		goto free_tsk;



	stack = alloc_thread_stack_node(tsk, node);

	if (!stack)

	err = alloc_thread_stack_node(tsk, node);

	if (err)

		goto free_tsk;



	if (memcg_charge_kernel_stack(tsk))

		goto free_stack;



	stack_vm_area = task_stack_vm_area(tsk);



	/*

	 * arch_dup_task_struct() clobbers the stack-related fields.  Make

	 * sure they're properly initialized before using any stack-related

	 * functions again.

	 */

	tsk->stack = stack;

#ifdef CONFIG_VMAP_STACK

	tsk->stack_vm_area = stack_vm_area;

#endif

#ifdef CONFIG_THREAD_INFO_IN_TASK

	refcount_set(&tsk->stack_refcount, 1);

#endif