Merge tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Borislav Petkov:
- Make sure sanity checks down in the mutex lock path happen on the
correct type of task so that they don't trigger falsely
- Use the write unsafe user access pairs when writing a futex value to
prevent an error on PowerPC which does user read and write accesses
differently
* tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking: Fix __clear_task_blocked_on() warning from __ww_mutex_wound() path
futex: Use user_write_access_begin/_end() in futex_put_value()
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2b27238..f8188b8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2152,6 +2152,8 @@ static inline struct mutex *__get_task_blocked_on(struct task_struct *p)
static inline void __set_task_blocked_on(struct task_struct *p, struct mutex *m)
{
+ struct mutex *blocked_on = READ_ONCE(p->blocked_on);
+
WARN_ON_ONCE(!m);
/* The task should only be setting itself as blocked */
WARN_ON_ONCE(p != current);
@@ -2162,8 +2164,8 @@ static inline void __set_task_blocked_on(struct task_struct *p, struct mutex *m)
* with a different mutex. Note, setting it to the same
* lock repeatedly is ok.
*/
- WARN_ON_ONCE(p->blocked_on && p->blocked_on != m);
- p->blocked_on = m;
+ WARN_ON_ONCE(blocked_on && blocked_on != m);
+ WRITE_ONCE(p->blocked_on, m);
}
static inline void set_task_blocked_on(struct task_struct *p, struct mutex *m)
@@ -2174,16 +2176,19 @@ static inline void set_task_blocked_on(struct task_struct *p, struct mutex *m)
static inline void __clear_task_blocked_on(struct task_struct *p, struct mutex *m)
{
- WARN_ON_ONCE(!m);
- /* Currently we serialize blocked_on under the mutex::wait_lock */
- lockdep_assert_held_once(&m->wait_lock);
- /*
- * There may be cases where we re-clear already cleared
- * blocked_on relationships, but make sure we are not
- * clearing the relationship with a different lock.
- */
- WARN_ON_ONCE(m && p->blocked_on && p->blocked_on != m);
- p->blocked_on = NULL;
+ if (m) {
+ struct mutex *blocked_on = READ_ONCE(p->blocked_on);
+
+ /* Currently we serialize blocked_on under the mutex::wait_lock */
+ lockdep_assert_held_once(&m->wait_lock);
+ /*
+ * There may be cases where we re-clear already cleared
+ * blocked_on relationships, but make sure we are not
+ * clearing the relationship with a different lock.
+ */
+ WARN_ON_ONCE(blocked_on && blocked_on != m);
+ }
+ WRITE_ONCE(p->blocked_on, NULL);
}
static inline void clear_task_blocked_on(struct task_struct *p, struct mutex *m)
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index c74eac5..2cd5709 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -319,13 +319,13 @@ static __always_inline int futex_put_value(u32 val, u32 __user *to)
{
if (can_do_masked_user_access())
to = masked_user_access_begin(to);
- else if (!user_read_access_begin(to, sizeof(*to)))
+ else if (!user_write_access_begin(to, sizeof(*to)))
return -EFAULT;
unsafe_put_user(val, to, Efault);
- user_read_access_end();
+ user_write_access_end();
return 0;
Efault:
- user_read_access_end();
+ user_write_access_end();
return -EFAULT;
}
diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
index 086fd54..31a785a 100644
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -342,8 +342,12 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
* When waking up the task to wound, be sure to clear the
* blocked_on pointer. Otherwise we can see circular
* blocked_on relationships that can't resolve.
+ *
+ * NOTE: We pass NULL here instead of lock, because we
+ * are waking the mutex owner, who may be currently
+ * blocked on a different mutex.
*/
- __clear_task_blocked_on(owner, lock);
+ __clear_task_blocked_on(owner, NULL);
wake_q_add(wake_q, owner);
}
return true;
