Merge tag 'locking_urgent_for_v6.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

torvalds · torvalds · commit 753a0f61b909 · 2025-06-29T08:09:13.000-07:00
Pull locking fix from Borislav Petkov:

 - Make sure the new futex phash is not copied during fork in order to
   avoid a double-free

* tag 'locking_urgent_for_v6.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Initialize futex_phash_new during fork().
diff --git a/include/linux/futex.h b/include/linux/futex.h
@@ -89,6 +89,7 @@ void futex_hash_free(struct mm_struct *mm);
 static inline void futex_mm_init(struct mm_struct *mm)
 {
 	RCU_INIT_POINTER(mm->futex_phash, NULL);
+	mm->futex_phash_new = NULL;
 	mutex_init(&mm->futex_hash_lock);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -89,6 +89,7 @@ void futex_hash_free(struct mm_struct *mm);`
`89`	`89`	`static inline void futex_mm_init(struct mm_struct *mm)`
`90`	`90`	`{`
`91`	`91`	`RCU_INIT_POINTER(mm->futex_phash, NULL);`
	`92`	`+ mm->futex_phash_new = NULL;`
`92`	`93`	`mutex_init(&mm->futex_hash_lock);`
`93`	`94`	`}`
`94`	`95`