[PATCH 4.14 187/209] futex: Move futex exit handling into futex code

Greg Kroah-Hartman
2019-12-04T18:20:05Z

From: Thomas Gleixner <tglx@linutronix.de>

commit ba31c1a48538992316cc71ce94fa9cd3e7b427c0 upstream.

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: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.049705556@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/compat.h | 2 --
include/linux/futex.h | 25 ++++++++++++++++---------
kernel/fork.c | 25 +++----------------------
kernel/futex.c | 33 +++++++++++++++++++++++++++++----
4 files changed, 48 insertions(+), 37 deletions(-)

--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -324,8 +324,6 @@ struct compat_kexec_segment;
struct compat_mq_attr;
struct compat_msgbuf;

-extern void compat_exit_robust_list(struct task_struct *curr);
-
asmlinkage long
compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
compat_size_t len);
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -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;
@@ -51,19 +53,24 @@ 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);
-#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;
+}

-#ifdef CONFIG_FUTEX_PI
-extern void exit_pi_state_list(struct task_struct *curr);
+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 exit_pi_state_list(struct task_struct *curr)
-{
-}
+static inline void futex_init_task(struct task_struct *tsk) { }
+static inline void futex_mm_release(struct task_struct *tsk) { }
#endif

#endif
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1135,20 +1135,7 @@ static int wait_for_vfork_done(struct ta
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);

@@ -1796,14 +1783,8 @@ static __latent_entropy struct task_stru
#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
*/
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -341,6 +341,12 @@ static inline bool should_fail_futex(boo
}
#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 struct task_struct *futex_find_ge
* 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_stru
}
raw_spin_unlock_irq(&curr->pi_lock);
}
-
+#else
+static inline void exit_pi_state_list(struct task_struct *curr) { }
#endif

/*
@@ -3611,7 +3618,7 @@ static inline int fetch_robust_entry(str
*
* 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;
@@ -3676,6 +3683,24 @@ void exit_robust_list(struct task_struct
}
}

+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)
{
@@ -3801,7 +3826,7 @@ static void __user *futex_uaddr(struct r
*
* 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;