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Commit 99cf9fa9 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Zubin Mithra
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UPSTREAM: sched/core: Add try_get_task_stack() and put_task_stack() 



There are a few places in the kernel that access stack memory
belonging to a different task.  Before we can start freeing task
stacks before the task_struct is freed, we need a way for those code
paths to pin the stack.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jann Horn <jann@thejh.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/17a434f50ad3d77000104f21666575e10a9c1fbd.1474003868.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>

Bug: 38331309
Change-Id: I414853e9b72ecb0967d5e1cbfc77b4929bf3f4f5
(cherry picked from commit c6c314a613cd7d03fb97713e0d642b493de42e69)
Signed-off-by: default avatarZubin Mithra <zsm@google.com>
parent 8bc69d46

include/linux/sched.h

+16 −0
Original line number Diff line number Diff line
@@ -2964,11 +2964,19 @@ static inline struct thread_info *task_thread_info(struct task_struct *task) 
{

	return &task->thread_info;

}



/*

 * When accessing the stack of a non-current task that might exit, use

 * try_get_task_stack() instead.  task_stack_page will return a pointer

 * that could get freed out from under you.

 */

static inline void *task_stack_page(const struct task_struct *task)

{

	return task->stack;

}



#define setup_thread_stack(new,old)	do { } while(0)



static inline unsigned long *end_of_stack(const struct task_struct *task)

{

	return task->stack;
@@ -3004,6 +3012,14 @@ static inline unsigned long *end_of_stack(struct task_struct *p) 
}



#endif



static inline void *try_get_task_stack(struct task_struct *tsk)

{

	return task_stack_page(tsk);

}



static inline void put_task_stack(struct task_struct *tsk) {}



#define task_stack_end_corrupted(task) \

		(*(end_of_stack(task)) != STACK_END_MAGIC)

init/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -33,6 +33,9 @@ config THREAD_INFO_IN_TASK 
	  make this work, an arch will need to remove all thread_info fields

	  except flags and fix any runtime bugs.



	  One subtle change that will be needed is to use try_get_task_stack()

	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().



menu "General setup"



config BROKEN