Commit ba31c1a4 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

futex: Move futex exit handling into futex code 



The futex exit handling is #ifdeffed into mm_release() which is not pretty
to begin with. But upcoming changes to address futex exit races need to add
more functionality to this exit code.

Split it out into a function, move it into futex code and make the various
futex exit functions static.

Preparatory only and no functional change.

Folded build fix from Borislav.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.049705556@linutronix.de
parent ca16d5be

include/linux/compat.h

+0 −2
Original line number Diff line number Diff line
@@ -410,8 +410,6 @@ struct compat_kexec_segment; 
struct compat_mq_attr;

struct compat_msgbuf;



extern void compat_exit_robust_list(struct task_struct *curr);



#define BITS_PER_COMPAT_LONG    (8*sizeof(compat_long_t))



#define BITS_TO_COMPAT_LONGS(bits) DIV_ROUND_UP(bits, BITS_PER_COMPAT_LONG)

include/linux/futex.h

+16 −13
Original line number Diff line number Diff line
@@ -2,7 +2,9 @@ 
#ifndef _LINUX_FUTEX_H

#define _LINUX_FUTEX_H



#include <linux/sched.h>

#include <linux/ktime.h>



#include <uapi/linux/futex.h>



struct inode;
@@ -48,15 +50,24 @@ union futex_key { 
#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }



#ifdef CONFIG_FUTEX

extern void exit_robust_list(struct task_struct *curr);



long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,

	      u32 __user *uaddr2, u32 val2, u32 val3);

#else

static inline void exit_robust_list(struct task_struct *curr)

static inline void futex_init_task(struct task_struct *tsk)

{

	tsk->robust_list = NULL;

#ifdef CONFIG_COMPAT

	tsk->compat_robust_list = NULL;

#endif

	INIT_LIST_HEAD(&tsk->pi_state_list);

	tsk->pi_state_cache = NULL;

}



void futex_mm_release(struct task_struct *tsk);



long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,

	      u32 __user *uaddr2, u32 val2, u32 val3);

#else

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

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

static inline long do_futex(u32 __user *uaddr, int op, u32 val,

			    ktime_t *timeout, u32 __user *uaddr2,

			    u32 val2, u32 val3)
@@ -65,12 +76,4 @@ static inline long do_futex(u32 __user *uaddr, int op, u32 val, 
}

#endif



#ifdef CONFIG_FUTEX_PI

extern void exit_pi_state_list(struct task_struct *curr);

#else

static inline void exit_pi_state_list(struct task_struct *curr)

{

}

#endif



#endif

kernel/fork.c

+3 −22
Original line number Diff line number Diff line
@@ -1286,20 +1286,7 @@ static int wait_for_vfork_done(struct task_struct *child, 
void mm_release(struct task_struct *tsk, struct mm_struct *mm)

{

	/* Get rid of any futexes when releasing the mm */

#ifdef CONFIG_FUTEX

	if (unlikely(tsk->robust_list)) {

		exit_robust_list(tsk);

		tsk->robust_list = NULL;

	}

#ifdef CONFIG_COMPAT

	if (unlikely(tsk->compat_robust_list)) {

		compat_exit_robust_list(tsk);

		tsk->compat_robust_list = NULL;

	}

#endif

	if (unlikely(!list_empty(&tsk->pi_state_list)))

		exit_pi_state_list(tsk);

#endif

	futex_mm_release(tsk);



	uprobe_free_utask(tsk);
@@ -2062,14 +2049,8 @@ static __latent_entropy struct task_struct *copy_process( 
#ifdef CONFIG_BLOCK

	p->plug = NULL;

#endif

#ifdef CONFIG_FUTEX

	p->robust_list = NULL;

#ifdef CONFIG_COMPAT

	p->compat_robust_list = NULL;

#endif

	INIT_LIST_HEAD(&p->pi_state_list);

	p->pi_state_cache = NULL;

#endif

	futex_init_task(p);



	/*

	 * sigaltstack should be cleared when sharing the same VM

	 */

kernel/futex.c

+29 −4
Original line number Diff line number Diff line
@@ -325,6 +325,12 @@ static inline bool should_fail_futex(bool fshared) 
}

#endif /* CONFIG_FAIL_FUTEX */



#ifdef CONFIG_COMPAT

static void compat_exit_robust_list(struct task_struct *curr);

#else

static inline void compat_exit_robust_list(struct task_struct *curr) { }

#endif



static inline void futex_get_mm(union futex_key *key)

{

	mmgrab(key->private.mm);
@@ -890,7 +896,7 @@ static void put_pi_state(struct futex_pi_state *pi_state) 
 * Kernel cleans up PI-state, but userspace is likely hosed.

 * (Robust-futex cleanup is separate and might save the day for userspace.)

 */

void exit_pi_state_list(struct task_struct *curr)

static void exit_pi_state_list(struct task_struct *curr)

{

	struct list_head *next, *head = &curr->pi_state_list;

	struct futex_pi_state *pi_state;
@@ -960,7 +966,8 @@ void exit_pi_state_list(struct task_struct *curr) 
	}

	raw_spin_unlock_irq(&curr->pi_lock);

}



#else

static inline void exit_pi_state_list(struct task_struct *curr) { }

#endif



/*
@@ -3588,7 +3595,7 @@ static inline int fetch_robust_entry(struct robust_list __user **entry, 
 *

 * We silently return on any sign of list-walking problem.

 */

void exit_robust_list(struct task_struct *curr)

static void exit_robust_list(struct task_struct *curr)

{

	struct robust_list_head __user *head = curr->robust_list;

	struct robust_list __user *entry, *next_entry, *pending;
@@ -3653,6 +3660,24 @@ void exit_robust_list(struct task_struct *curr) 
	}

}



void futex_mm_release(struct task_struct *tsk)

{

	if (unlikely(tsk->robust_list)) {

		exit_robust_list(tsk);

		tsk->robust_list = NULL;

	}



#ifdef CONFIG_COMPAT

	if (unlikely(tsk->compat_robust_list)) {

		compat_exit_robust_list(tsk);

		tsk->compat_robust_list = NULL;

	}

#endif



	if (unlikely(!list_empty(&tsk->pi_state_list)))

		exit_pi_state_list(tsk);

}



long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,

		u32 __user *uaddr2, u32 val2, u32 val3)

{
@@ -3780,7 +3805,7 @@ static void __user *futex_uaddr(struct robust_list __user *entry, 
 *

 * We silently return on any sign of list-walking problem.

 */

void compat_exit_robust_list(struct task_struct *curr)

static void compat_exit_robust_list(struct task_struct *curr)

{

	struct compat_robust_list_head __user *head = curr->compat_robust_list;

	struct robust_list __user *entry, *next_entry, *pending;

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