On Mon, Mar 15, 2021 at 06:16:28PM -0700, Li Li wrote:
> From: Marco Ballesio <bal...@google.com>
>
> Frozen tasks can't process binder transactions, so a way is required to
> inform transmitting ends of communication failures due to the frozen
> state of their receiving counterparts. Additionally, races are possible
> between transitions to frozen state and binder transactions enqueued to
> a specific process.
>
> Implement BINDER_FREEZE ioctl for user space to inform the binder driver
> about the intention to freeze or unfreeze a process. When the ioctl is
> called, block the caller until any pending binder transactions toward
> the target process are flushed. Return an error to transactions to
> processes marked as frozen.
>
> Signed-off-by: Marco Ballesio <bal...@google.com>
> Co-developed-by: Todd Kjos <tk...@google.com>
> Signed-off-by: Todd Kjos <tk...@google.com>
> Signed-off-by: Li Li <dua...@google.com>
> ---
> drivers/android/binder.c | 139 ++++++++++++++++++++++++++--
> drivers/android/binder_internal.h | 12 +++
> include/uapi/linux/android/binder.h | 13 +++
> 3 files changed, 154 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index c119736ca56a..b93ca53bb90f 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -1506,6 +1506,12 @@ static void binder_free_transaction(struct
> binder_transaction *t)
>
> if (target_proc) {
> binder_inner_proc_lock(target_proc);
> + target_proc->outstanding_txns--;
> + if (target_proc->outstanding_txns < 0)
> + pr_warn("%s: Unexpected outstanding_txns %d\n",
> + __func__, target_proc->outstanding_txns);
> + if (!target_proc->outstanding_txns && target_proc->is_frozen)
> + wake_up_interruptible_all(&target_proc->freeze_wait);
> if (t->buffer)
> t->buffer->transaction = NULL;
> binder_inner_proc_unlock(target_proc);
> @@ -2331,10 +2337,11 @@ static int binder_fixup_parent(struct
> binder_transaction *t,
> * If the @thread parameter is not NULL, the transaction is always queued
> * to the waitlist of that specific thread.
> *
> - * Return: true if the transactions was successfully queued
> - * false if the target process or thread is dead
> + * Return: 0 if the transaction was successfully queued
> + * BR_DEAD_REPLY if the target process or thread is dead
> + * BR_FROZEN_REPLY if the target process or thread is frozen
> */
> -static bool binder_proc_transaction(struct binder_transaction *t,
> +static int binder_proc_transaction(struct binder_transaction *t,
> struct binder_proc *proc,
> struct binder_thread *thread)
> {
> @@ -2354,10 +2361,11 @@ static bool binder_proc_transaction(struct
> binder_transaction *t,
>
> binder_inner_proc_lock(proc);
>
> - if (proc->is_dead || (thread && thread->is_dead)) {
> + if ((proc->is_frozen && !oneway) || proc->is_dead ||
> + (thread && thread->is_dead)) {
> binder_inner_proc_unlock(proc);
> binder_node_unlock(node);
> - return false;
> + return proc->is_frozen ? BR_FROZEN_REPLY : BR_DEAD_REPLY;
> }
>
> if (!thread && !pending_async)
> @@ -2373,10 +2381,11 @@ static bool binder_proc_transaction(struct
> binder_transaction *t,
> if (!pending_async)
> binder_wakeup_thread_ilocked(proc, thread, !oneway /* sync */);
>
> + proc->outstanding_txns++;
> binder_inner_proc_unlock(proc);
> binder_node_unlock(node);
>
> - return true;
> + return 0;
> }
>
> /**
> @@ -3013,13 +3022,16 @@ static void binder_transaction(struct binder_proc
> *proc,
> if (reply) {
> binder_enqueue_thread_work(thread, tcomplete);
> binder_inner_proc_lock(target_proc);
> - if (target_thread->is_dead) {
> + if (target_thread->is_dead || target_proc->is_frozen) {
> + return_error = target_thread->is_dead ?
> + BR_DEAD_REPLY : BR_FROZEN_REPLY;
> binder_inner_proc_unlock(target_proc);
> goto err_dead_proc_or_thread;
> }
> BUG_ON(t->buffer->async_transaction != 0);
> binder_pop_transaction_ilocked(target_thread, in_reply_to);
> binder_enqueue_thread_work_ilocked(target_thread, &t->work);
> + target_proc->outstanding_txns++;
> binder_inner_proc_unlock(target_proc);
> wake_up_interruptible_sync(&target_thread->wait);
> binder_free_transaction(in_reply_to);
> @@ -3038,7 +3050,9 @@ static void binder_transaction(struct binder_proc *proc,
> t->from_parent = thread->transaction_stack;
> thread->transaction_stack = t;
> binder_inner_proc_unlock(proc);
> - if (!binder_proc_transaction(t, target_proc, target_thread)) {
> + return_error = binder_proc_transaction(t,
> + target_proc, target_thread);
> + if (return_error) {
> binder_inner_proc_lock(proc);
> binder_pop_transaction_ilocked(thread, t);
> binder_inner_proc_unlock(proc);
> @@ -3048,7 +3062,8 @@ static void binder_transaction(struct binder_proc *proc,
> BUG_ON(target_node == NULL);
> BUG_ON(t->buffer->async_transaction != 1);
> binder_enqueue_thread_work(thread, tcomplete);
> - if (!binder_proc_transaction(t, target_proc, NULL))
> + return_error = binder_proc_transaction(t, target_proc, NULL);
> + if (return_error)
> goto err_dead_proc_or_thread;
> }
> if (target_thread)
> @@ -3065,7 +3080,6 @@ static void binder_transaction(struct binder_proc *proc,
> return;
>
> err_dead_proc_or_thread:
> - return_error = BR_DEAD_REPLY;
> return_error_line = __LINE__;
> binder_dequeue_work(proc, tcomplete);
> err_translate_failed:
> @@ -4298,6 +4312,9 @@ static void binder_free_proc(struct binder_proc *proc)
>
> BUG_ON(!list_empty(&proc->todo));
> BUG_ON(!list_empty(&proc->delivered_death));
> + if (proc->outstanding_txns)
> + pr_warn("%s: Unexpected outstanding_txns %d\n",
> + __func__, proc->outstanding_txns);
> device = container_of(proc->context, struct binder_device, context);
> if (refcount_dec_and_test(&device->ref)) {
> kfree(proc->context->name);
> @@ -4359,6 +4376,7 @@ static int binder_thread_release(struct binder_proc
> *proc,
> (t->to_thread == thread) ? "in" : "out");
>
> if (t->to_thread == thread) {
> + thread->proc->outstanding_txns--;
> t->to_proc = NULL;
> t->to_thread = NULL;
> if (t->buffer) {
> @@ -4609,6 +4627,45 @@ static int binder_ioctl_get_node_debug_info(struct
> binder_proc *proc,
> return 0;
> }
>
> +static int binder_ioctl_freeze(struct binder_freeze_info *info,
> + struct binder_proc *target_proc)
> +{
> + int ret = 0;
> +
> + if (!info->enable) {
> + binder_inner_proc_lock(target_proc);
> + target_proc->is_frozen = false;
> + binder_inner_proc_unlock(target_proc);
> + return 0;
> + }
> +
> + /*
> + * Freezing the target. Prevent new transactions by
> + * setting frozen state. If timeout specified, wait
> + * for transactions to drain.
> + */
> + binder_inner_proc_lock(target_proc);
> + target_proc->is_frozen = true;
> + binder_inner_proc_unlock(target_proc);
> +
> + if (info->timeout_ms > 0)
> + ret = wait_event_interruptible_timeout(
> + target_proc->freeze_wait,
> + (!target_proc->outstanding_txns),
> + msecs_to_jiffies(info->timeout_ms));
> +
> + if (!ret && target_proc->outstanding_txns)
> + ret = -EAGAIN;
> +
> + if (ret < 0) {
> + binder_inner_proc_lock(target_proc);
> + target_proc->is_frozen = false;
> + binder_inner_proc_unlock(target_proc);
> + }
> +
> + return ret;
> +}
> +
> static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long
> arg)
> {
> int ret;
> @@ -4727,6 +4784,66 @@ static long binder_ioctl(struct file *filp, unsigned
> int cmd, unsigned long arg)
> }
> break;
> }
> + case BINDER_FREEZE: {
> + struct binder_freeze_info info;
> + struct binder_proc **target_procs = NULL, *target_proc;
> + int target_procs_count = 0, i = 0;
> +
> + ret = 0;
> +
> + if (copy_from_user(&info, ubuf, sizeof(info))) {
This is not at all a blocker to this I just want to point out that if
you wanted to you could ensure that this API is extensible with
guaranteed forward- and backward compatibility by switching to the
copy_struct_from_user() API that Aleksa and I added and that is nowadays
used in a bunch of syscalls (openat2((), clone3(), mount_setattr(),
sched_setattr() etc.). For the seccomp notifier work we did we extended
this concept to ioctls(), see
kernel/seccomp.c:
static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct seccomp_filter *filter = file->private_data;
void __user *buf = (void __user *)arg;
/* Fixed-size ioctls */
switch (cmd) {
case SECCOMP_IOCTL_NOTIF_RECV:
return seccomp_notify_recv(filter, buf);
case SECCOMP_IOCTL_NOTIF_SEND:
return seccomp_notify_send(filter, buf);
case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR:
case SECCOMP_IOCTL_NOTIF_ID_VALID:
return seccomp_notify_id_valid(filter, buf);
}
/* Extensible Argument ioctls */
#define EA_IOCTL(cmd) ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
switch (EA_IOCTL(cmd)) {
case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD):
return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd));
default:
return -EINVAL;
}
}
Christian
