Update Linux to v5.10.109
Sourced from [1]
[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.109.tar.xz
Change-Id: I19bca9fc6762d4e63bcf3e4cba88bbe560d9c76c
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/ipc/sem.c b/ipc/sem.c
index fe12ea8..7d9c06b 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -205,15 +205,38 @@
*
* Memory ordering:
* Most ordering is enforced by using spin_lock() and spin_unlock().
- * The special case is use_global_lock:
+ *
+ * Exceptions:
+ * 1) use_global_lock: (SEM_BARRIER_1)
* Setting it from non-zero to 0 is a RELEASE, this is ensured by
- * using smp_store_release().
+ * using smp_store_release(): Immediately after setting it to 0,
+ * a simple op can start.
* Testing if it is non-zero is an ACQUIRE, this is ensured by using
* smp_load_acquire().
* Setting it from 0 to non-zero must be ordered with regards to
* this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
* is inside a spin_lock() and after a write from 0 to non-zero a
* spin_lock()+spin_unlock() is done.
+ *
+ * 2) queue.status: (SEM_BARRIER_2)
+ * Initialization is done while holding sem_lock(), so no further barrier is
+ * required.
+ * Setting it to a result code is a RELEASE, this is ensured by both a
+ * smp_store_release() (for case a) and while holding sem_lock()
+ * (for case b).
+ * The AQUIRE when reading the result code without holding sem_lock() is
+ * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
+ * (case a above).
+ * Reading the result code while holding sem_lock() needs no further barriers,
+ * the locks inside sem_lock() enforce ordering (case b above)
+ *
+ * 3) current->state:
+ * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
+ * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
+ * happen immediately after calling wake_q_add. As wake_q_add_safe() is called
+ * when holding sem_lock(), no further barriers are required.
+ *
+ * See also ipc/mqueue.c for more details on the covered races.
*/
#define sc_semmsl sem_ctls[0]
@@ -344,12 +367,8 @@
return;
}
if (sma->use_global_lock == 1) {
- /*
- * Immediately after setting use_global_lock to 0,
- * a simple op can start. Thus: all memory writes
- * performed by the current operation must be visible
- * before we set use_global_lock to 0.
- */
+
+ /* See SEM_BARRIER_1 for purpose/pairing */
smp_store_release(&sma->use_global_lock, 0);
} else {
sma->use_global_lock--;
@@ -400,7 +419,7 @@
*/
spin_lock(&sem->lock);
- /* pairs with smp_store_release() */
+ /* see SEM_BARRIER_1 for purpose/pairing */
if (!smp_load_acquire(&sma->use_global_lock)) {
/* fast path successful! */
return sops->sem_num;
@@ -566,8 +585,7 @@
/*
* Called with sem_ids.rwsem and ipcp locked.
*/
-static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
- struct ipc_params *params)
+static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
{
struct sem_array *sma;
@@ -766,15 +784,14 @@
static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
struct wake_q_head *wake_q)
{
- wake_q_add(wake_q, q->sleeper);
- /*
- * Rely on the above implicit barrier, such that we can
- * ensure that we hold reference to the task before setting
- * q->status. Otherwise we could race with do_exit if the
- * task is awoken by an external event before calling
- * wake_up_process().
- */
- WRITE_ONCE(q->status, error);
+ struct task_struct *sleeper;
+
+ sleeper = get_task_struct(q->sleeper);
+
+ /* see SEM_BARRIER_2 for purpuse/pairing */
+ smp_store_release(&q->status, error);
+
+ wake_q_add_safe(wake_q, sleeper);
}
static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
@@ -1676,7 +1693,7 @@
case IPC_SET:
if (copy_semid_from_user(&semid64, p, version))
return -EFAULT;
- /* fall through */
+ fallthrough;
case IPC_RMID:
return semctl_down(ns, semid, cmd, &semid64);
default:
@@ -1790,7 +1807,7 @@
case IPC_SET:
if (copy_compat_semid_from_user(&semid64, p, version))
return -EFAULT;
- /* fallthru */
+ fallthrough;
case IPC_RMID:
return semctl_down(ns, semid, cmd, &semid64);
default:
@@ -2148,9 +2165,11 @@
}
do {
+ /* memory ordering ensured by the lock in sem_lock() */
WRITE_ONCE(queue.status, -EINTR);
queue.sleeper = current;
+ /* memory ordering is ensured by the lock in sem_lock() */
__set_current_state(TASK_INTERRUPTIBLE);
sem_unlock(sma, locknum);
rcu_read_unlock();
@@ -2173,13 +2192,8 @@
*/
error = READ_ONCE(queue.status);
if (error != -EINTR) {
- /*
- * User space could assume that semop() is a memory
- * barrier: Without the mb(), the cpu could
- * speculatively read in userspace stale data that was
- * overwritten by the previous owner of the semaphore.
- */
- smp_mb();
+ /* see SEM_BARRIER_2 for purpose/pairing */
+ smp_acquire__after_ctrl_dep();
goto out_free;
}
@@ -2189,6 +2203,9 @@
if (!ipc_valid_object(&sma->sem_perm))
goto out_unlock_free;
+ /*
+ * No necessity for any barrier: We are protect by sem_lock()
+ */
error = READ_ONCE(queue.status);
/*