Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751445AbdIPFM0 (ORCPT ); Sat, 16 Sep 2017 01:12:26 -0400 Received: from mail-it0-f45.google.com ([209.85.214.45]:46475 "EHLO mail-it0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbdIPFMI (ORCPT ); Sat, 16 Sep 2017 01:12:08 -0400 X-Google-Smtp-Source: AOwi7QBLMl3dNj36FXuGSpEVs1KA8EpyE5rcPHe+qsaWCDUGHIs6CmTaftk9SGsJ08NLsM98ZSt4rQ== From: Sherry Yang To: linux-kernel@vger.kernel.org Cc: tkjos@google.com, maco@google.com, Sherry Yang , Greg Kroah-Hartman , =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Riley Andrews , devel@driverdev.osuosl.org (open list:ANDROID DRIVERS) Subject: [PATCH 2/2] android: binder: Don't get mm from task Date: Sat, 16 Sep 2017 01:11:57 -0400 Message-Id: <20170916051158.96588-3-sherryy@android.com> X-Mailer: git-send-email 2.11.0 (Apple Git-81) In-Reply-To: <20170916051158.96588-1-sherryy@android.com> References: <20170916051158.96588-1-sherryy@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3248 Lines: 106 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 Signed-off-by: Sherry Yang --- drivers/android/binder_alloc.c | 22 +++++++++------------- drivers/android/binder_alloc.h | 1 - 2 files changed, 9 insertions(+), 14 deletions(-) diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index b87ecf77f9d1..e283670695db 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 (need_mm) - mm = get_task_mm(alloc->tsk); + if (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) { @@ -718,6 +713,7 @@ 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; @@ -793,6 +789,8 @@ 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", @@ -887,7 +885,6 @@ 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); } /** @@ -924,9 +921,9 @@ 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; } @@ -961,7 +958,7 @@ 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: @@ -1000,7 +997,6 @@ 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); diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h index a3a3602c689c..2dd33b6df104 100644 --- a/drivers/android/binder_alloc.h +++ b/drivers/android/binder_alloc.h @@ -100,7 +100,6 @@ struct binder_lru_page { */ struct binder_alloc { struct mutex mutex; - struct task_struct *tsk; struct vm_area_struct *vma; struct mm_struct *vma_vm_mm; void *buffer; -- 2.11.0 (Apple Git-81)