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drm/i915/gt: Fix a double free in gen8_preallocate_top_level_pdp

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Our code analyzer reported a double free bug.

In gen8_preallocate_top_level_pdp, pde and pde->pt.base are allocated
via alloc_pd(vm) with one reference. If pin_pt_dma() failed, pde->pt.base
is freed by i915_gem_object_put() with a reference dropped. Then free_pd
calls free_px() defined in intel_ppgtt.c, which calls i915_gem_object_put()
to put pde->pt.base again.

As pde->pt.base is protected by refcount, so the second put will not free
pde->pt.base actually. But, maybe it is better to remove the first put?

Fixes: 82adf90113 ("drm/i915/gt: Shrink i915_page_directory's slab bucket")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210426124340.4238-1-lyl2019@mail.ustc.edu.cn
This commit is contained in:
Lv Yunlong 2021-04-26 05:43:40 -07:00 committed by Matthew Auld
parent 924ad0e848
commit ac69496fe6
1 changed files with 0 additions and 1 deletions
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drivers/gpu/drm/i915/gt/gen8_ppgtt.c
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@ -641,7 +641,6 @@ static int gen8_preallocate_top_level_pdp(struct i915_ppgtt *ppgtt)
err = pin_pt_dma(vm, pde->pt.base);
if (err) {
i915_gem_object_put(pde->pt.base);
free_pd(vm, pde);
return err;
}