futex: Move futex exit handling into futex code

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>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/compat.h b/include/linux/compat.h
index fab35daf87596e1a4fdcd4b2cdd395dc686b3de3..6b9d38a7adcafe4abcacb5137b9bec426136b74f 100644 (file)
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -311,8 +311,6 @@ 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);

diff --git a/include/linux/futex.h b/include/linux/futex.h
index fb4e12cbe887e0119d12e5bfa89ef6d15626c4b0..63d353cedfcde0a0f152aad4f98630c37c6e63db 100644 (file)
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -1,6 +1,8 @@
 #ifndef _LINUX_FUTEX_H
 #define _LINUX_FUTEX_H
 
+#include <linux/sched.h>
+
 #include <uapi/linux/futex.h>
 
 struct inode;
@@ -53,14 +55,22 @@ union futex_key {
 #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
 
 #ifdef CONFIG_FUTEX
-extern void exit_robust_list(struct task_struct *curr);
-extern void exit_pi_state_list(struct task_struct *curr);
-#else
-static inline void exit_robust_list(struct task_struct *curr)
-{
-}
-static inline void exit_pi_state_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) { }
 #endif
 #endif

diff --git a/kernel/fork.c b/kernel/fork.c
index b64efec4a6e6e29d39b874be84b7c112792581f9..000447bfcfde584e9228fb4e5239ff6c091f4d21 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1085,20 +1085,7 @@ 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);
 
@@ -1706,14 +1693,8 @@ 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 220e3924869b0227e8cf011206583c65a7c60075..156b23f4b9aac70819c134a5501df986964f957e 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -339,6 +339,12 @@ 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)
 {
        atomic_inc(&key->private.mm->mm_count);
@@ -894,7 +900,7 @@ static struct task_struct * futex_find_get_task(pid_t pid)
  * 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;
@@ -3201,7 +3207,7 @@ 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;
@@ -3264,6 +3270,24 @@ void exit_robust_list(struct task_struct *curr)
                                   curr, pip);
 }
 
+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)
 {