diff options
author | Sherry Yang <sherryy@android.com> | 2017-10-20 20:58:58 -0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-21 10:14:20 +0200 |
commit | a0c2baaf81bd53dc76fccdddc721ba7dbb62be21 (patch) | |
tree | 0104ebfb31019168be252bc006e4689674cd8dcf /drivers/android/binder_alloc.c | |
parent | 9d35593b4f0b89ab0c194349c7d357b3b159e99a (diff) | |
download | op-kernel-dev-a0c2baaf81bd53dc76fccdddc721ba7dbb62be21.zip op-kernel-dev-a0c2baaf81bd53dc76fccdddc721ba7dbb62be21.tar.gz |
android: binder: Don't get mm from task
Use binder_alloc struct's mm_struct rather than getting
a reference to the mm struct through get_task_mm to
avoid a potential deadlock between lru lock, task lock and
dentry lock, since a thread can be holding the task lock
and the dentry lock while trying to acquire the lru lock.
Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android/binder_alloc.c')
-rw-r--r-- | drivers/android/binder_alloc.c | 22 |
1 files changed, 9 insertions, 13 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 064f5e3..e12072b 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -215,17 +215,12 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, } } - if (!vma && need_mm) - mm = get_task_mm(alloc->tsk); + if (!vma && need_mm && mmget_not_zero(alloc->vma_vm_mm)) + mm = alloc->vma_vm_mm; if (mm) { down_write(&mm->mmap_sem); vma = alloc->vma; - if (vma && mm != alloc->vma_vm_mm) { - pr_err("%d: vma mm and task mm mismatch\n", - alloc->pid); - vma = NULL; - } } if (!vma && need_mm) { @@ -720,6 +715,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, barrier(); alloc->vma = vma; alloc->vma_vm_mm = vma->vm_mm; + mmgrab(alloc->vma_vm_mm); return 0; @@ -795,6 +791,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc) vfree(alloc->buffer); } mutex_unlock(&alloc->mutex); + if (alloc->vma_vm_mm) + mmdrop(alloc->vma_vm_mm); binder_alloc_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d buffers %d, pages %d\n", @@ -889,7 +887,6 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc) void binder_alloc_vma_close(struct binder_alloc *alloc) { WRITE_ONCE(alloc->vma, NULL); - WRITE_ONCE(alloc->vma_vm_mm, NULL); } /** @@ -926,9 +923,9 @@ enum lru_status binder_alloc_free_page(struct list_head *item, page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE; vma = alloc->vma; if (vma) { - mm = get_task_mm(alloc->tsk); - if (!mm) - goto err_get_task_mm_failed; + if (!mmget_not_zero(alloc->vma_vm_mm)) + goto err_mmget; + mm = alloc->vma_vm_mm; if (!down_write_trylock(&mm->mmap_sem)) goto err_down_write_mmap_sem_failed; } @@ -963,7 +960,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item, err_down_write_mmap_sem_failed: mmput_async(mm); -err_get_task_mm_failed: +err_mmget: err_page_already_freed: mutex_unlock(&alloc->mutex); err_get_alloc_mutex_failed: @@ -1002,7 +999,6 @@ struct shrinker binder_shrinker = { */ void binder_alloc_init(struct binder_alloc *alloc) { - alloc->tsk = current->group_leader; alloc->pid = current->group_leader->pid; mutex_init(&alloc->mutex); INIT_LIST_HEAD(&alloc->buffers); |