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 <[email protected]> Reviewed-by: Ingo Molnar <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Lee Jones <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
dashbaord202401 · Feb 3, 2021 · 8d2b511 · 8d2b511
1 parent ad940f6
commit 8d2b511
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Showing 4 changed files with 46 additions and 33 deletions.
diff --git a/include/linux/compat.h b/include/linux/compat.h
@@ -306,8 +306,6 @@ 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
@@ -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
@@ -890,20 +890,7 @@ 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);
 
@@ -1511,14 +1498,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 #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
@@ -331,6 +331,12 @@ 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);
@@ -889,7 +895,7 @@ 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;
@@ -3166,7 +3172,7 @@ 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;
@@ -3229,6 +3235,24 @@ 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)
 {