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

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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>
This commit is contained in:
Nicolai Hähnle 2017-02-14 09:37:12 +01:00 committed by Alex Deucher
parent 5ebbac4b5c
commit c2c139cf43
1 changed files with 7 additions and 5 deletions
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12
drivers/gpu/drm/ttm/ttm_bo.c
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@ -1188,18 +1188,20 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
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);