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Subject[tip: locking/core] futex: Move futex exit handling into futex code
The following commit has been merged into the locking/core branch of tip:

Commit-ID: 01e06025a2f81d7b797916a1b34731c6de0cf2e3
Gitweb: https://git.kernel.org/tip/01e06025a2f81d7b797916a1b34731c6de0cf2e3
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 06 Nov 2019 22:55:36 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Fri, 15 Nov 2019 19:10:49 +01:00

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.

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

---
include/linux/compat.h | 2 --
include/linux/futex.h | 27 ++++++++++++++-------------
kernel/fork.c | 25 +++----------------------
kernel/futex.c | 33 +++++++++++++++++++++++++++++----
4 files changed, 46 insertions(+), 41 deletions(-)

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 16dafd9..c4c389c 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -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)
diff --git a/include/linux/futex.h b/include/linux/futex.h
index ccaef00..2ffbb9c 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -48,15 +48,24 @@ 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 +74,4 @@ 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
diff --git a/kernel/fork.c b/kernel/fork.c
index bcdf531..bd7c218 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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
*/
diff --git a/kernel/futex.c b/kernel/futex.c
index 49eaf5b..f8f00d4 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -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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