Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755288AbaDTC2W (ORCPT ); Sat, 19 Apr 2014 22:28:22 -0400 Received: from g2t2353.austin.hp.com ([15.217.128.52]:57934 "EHLO g2t2353.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755236AbaDTC04 (ORCPT ); Sat, 19 Apr 2014 22:26:56 -0400 From: Davidlohr Bueso To: akpm@linux-foundation.org Cc: zeus@gnu.org, aswin@hp.com, davidlohr@hp.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Inki Dae , Joonyoung Shim , David Airlie , dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org Subject: [PATCH 6/6] drm/exynos: call find_vma with the mmap_sem held Date: Sat, 19 Apr 2014 19:26:31 -0700 Message-Id: <1397960791-16320-7-git-send-email-davidlohr@hp.com> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1397960791-16320-1-git-send-email-davidlohr@hp.com> References: <1397960791-16320-1-git-send-email-davidlohr@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jonathan Gonzalez V Performing vma lookups without taking the mm->mmap_sem is asking for trouble. While doing the search, the vma in question can be modified or even removed before returning to the caller. Take the lock (exclusively) in order to avoid races while iterating through the vmacache and/or rbtree. This patch is completely *untested*. Signed-off-by: Jonathan Gonzalez V Signed-off-by: Davidlohr Bueso Cc: Inki Dae Cc: Joonyoung Shim Cc: David Airlie Cc: dri-devel@lists.freedesktop.org Cc: linux-samsung-soc@vger.kernel.org --- drivers/gpu/drm/exynos/exynos_drm_g2d.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c index 6c1885e..8001587 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c @@ -467,14 +467,17 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev, goto err_free; } + down_read(¤t->mm->mmap_sem); vma = find_vma(current->mm, userptr); if (!vma) { + up_read(¤t->mm->mmap_sem); DRM_ERROR("failed to get vm region.\n"); ret = -EFAULT; goto err_free_pages; } if (vma->vm_end < userptr + size) { + up_read(¤t->mm->mmap_sem); DRM_ERROR("vma is too small.\n"); ret = -EFAULT; goto err_free_pages; @@ -482,6 +485,7 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev, g2d_userptr->vma = exynos_gem_get_vma(vma); if (!g2d_userptr->vma) { + up_read(¤t->mm->mmap_sem); DRM_ERROR("failed to copy vma.\n"); ret = -ENOMEM; goto err_free_pages; @@ -492,10 +496,12 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev, ret = exynos_gem_get_pages_from_userptr(start & PAGE_MASK, npages, pages, vma); if (ret < 0) { + up_read(¤t->mm->mmap_sem); DRM_ERROR("failed to get user pages from userptr.\n"); goto err_put_vma; } + up_read(¤t->mm->mmap_sem); g2d_userptr->pages = pages; sgt = kzalloc(sizeof(*sgt), GFP_KERNEL); -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/