This is a note to let you know that I've just added the patch titled

drm/ttm: never add BO that failed to validate to the LRU list

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: drm-ttm-never-add-bo-that-failed-to-validate-to-the-lru-list.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Sun Mar 18 16:55:33 CET 2018

From: "Nicolai Hähnle" nicolai.haehnle@amd.com Date: Tue, 14 Feb 2017 09:37:12 +0100 Subject: drm/ttm: never add BO that failed to validate to the LRU list

From: "Nicolai Hähnle" nicolai.haehnle@amd.com

[ Upstream commit c2c139cf435b18939204800fa72c53a7207bdd68 ]

Fixes a potential race condition in amdgpu that looks as follows:

Task 1: attempt ttm_bo_init, but ttm_bo_validate fails Task 1: add BO to global list anyway Task 2: grabs hold of the BO, waits on its reservation lock Task 1: releases its reference of the BO; never gives up the reservation lock

The patch "drm/amdgpu: fix a potential deadlock in amdgpu_bo_create_restricted()" attempts to fix that by releasing the reservation lock in amdgpu code; unfortunately, it introduces a use-after-free when this race _doesn't_ happen.

This patch should fix the race properly by never adding the BO to the global list in the first place.

Cc: zhoucm1 david1.zhou@amd.com Signed-off-by: Nicolai Hähnle nicolai.haehnle@amd.com Tested-by: Samuel Pitoiset samuel.pitoiset@gmail.com Reviewed-by: Christian König christian.koenig@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/ttm/ttm_bo.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -1209,18 +1209,20 @@ int ttm_bo_init(struct ttm_bo_device *bd if (likely(!ret)) ret = ttm_bo_validate(bo, placement, interruptible, false);

- if (!resv) { + if (!resv) ttm_bo_unreserve(bo);

- } else if (!(bo->mem.placement & TTM_PL_FLAG_NO_EVICT)) { + if (unlikely(ret)) { + ttm_bo_unref(&bo); + return ret; + } + + if (resv && !(bo->mem.placement & TTM_PL_FLAG_NO_EVICT)) { spin_lock(&bo->glob->lru_lock); ttm_bo_add_to_lru(bo); spin_unlock(&bo->glob->lru_lock); }

- if (unlikely(ret)) - ttm_bo_unref(&bo); - return ret; } EXPORT_SYMBOL(ttm_bo_init);

Patches currently in stable-queue which might be from nicolai.haehnle@amd.com are

queue-4.9/drm-ttm-never-add-bo-that-failed-to-validate-to-the-lru-list.patch