Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] drm/msm: NULL deref in get_pages() error path via drm_prime_gem_destroy() - [High] drm/msm: double dma_map/unmap_sgtable() in get_pages() and put_pages() --
commit 5b4a3d83276519e9cb8831bdfa37a513b1d334a3 Author: Rob Clark <[email protected]> drm/msm/gem: dma_map/unmap_sgtable() This commit adds dma_map_sgtable() and dma_unmap_sgtable() calls in get_pages() and put_pages() to populate the sgtable's dma_address and dma_len fields for setting up pagetable mappings. > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c > index 181b9ad326729..72e3cd8bb1e7c 100644 > --- a/drivers/gpu/drm/msm/msm_gem.c > +++ b/drivers/gpu/drm/msm/msm_gem.c > @@ -219,6 +219,15 @@ static struct page **get_pages(struct drm_gem_object > *obj) > goto error; > } > > + ret = dma_map_sgtable(drm_dev_dma_dev(obj->dev), > + msm_obj->sgt, > + DMA_BIDIRECTIONAL, > + DMA_ATTR_SKIP_CPU_SYNC); > + if (ret) { > + DRM_DEV_ERROR(dev->dev, "could not map sgtable: %d\n", > ret); > + goto error; > + } > + > update_device_mem(dev->dev_private, obj->size); > > /* For non-cached buffers, ensure the new pages are clean > @@ -233,6 +242,8 @@ static struct page **get_pages(struct drm_gem_object *obj) > return msm_obj->pages; > > error: > + if (!IS_ERR(msm_obj->sgt)) > + drm_prime_gem_destroy(obj, msm_obj->sgt); [Severity: High] Will calling drm_prime_gem_destroy() here dereference a NULL pointer and leak msm_obj->sgt when dma_map_sgtable() fails? At the start of get_pages(), imported DMA-BUF objects are rejected: drivers/gpu/drm/msm/msm_gem.c:get_pages() if (drm_WARN_ON_ONCE(obj->dev, drm_gem_is_imported(obj))) return ERR_PTR(-EINVAL); Because get_pages() only runs on native GEM objects, obj->import_attach is always NULL and msm_obj->sgt is allocated via drm_prime_pages_to_sg(). If dma_map_sgtable() fails and jumps to error, drm_prime_gem_destroy() is called with a valid msm_obj->sgt, which then dereferences attach (NULL) at attach->dmabuf while obj->resv is held, and fails to free msm_obj->sgt: drivers/gpu/drm/drm_prime.c:drm_prime_gem_destroy() attach = obj->import_attach; if (sg) dma_buf_unmap_attachment_unlocked(attach, sg, DMA_BIDIRECTIONAL); dma_buf = attach->dmabuf; Should the error path instead free msm_obj->sgt with sg_free_table(msm_obj->sgt) and kfree(msm_obj->sgt) to match put_pages()? > msm_obj->sgt = NULL; > > drm_gem_put_pages(obj, msm_obj->pages, false, false); > @@ -260,6 +271,11 @@ static void put_pages(struct drm_gem_object *obj) > if (msm_obj->flags & MSM_BO_WC) > sync_for_cpu(msm_obj); > > + dma_unmap_sgtable(drm_dev_dma_dev(obj->dev), > + msm_obj->sgt, > + DMA_BIDIRECTIONAL, > + DMA_ATTR_SKIP_CPU_SYNC); [Severity: High] Does this map and unmap msm_obj->sgt twice whenever MSM_BO_WC is set? In get_pages(), right after dma_map_sgtable() maps msm_obj->sgt with DMA_ATTR_SKIP_CPU_SYNC, objects with MSM_BO_WC call sync_for_device(): drivers/gpu/drm/msm/msm_gem.c:get_pages() if (msm_obj->flags & MSM_BO_WC) sync_for_device(msm_obj); And in put_pages(), before the new dma_unmap_sgtable() call, MSM_BO_WC objects call sync_for_cpu(). However, sync_for_device() and sync_for_cpu() themselves call dma_map_sgtable() and dma_unmap_sgtable() on the same msm_obj->sgt and device: drivers/gpu/drm/msm/msm_gem.c: static void sync_for_device(struct msm_gem_object *msm_obj) { struct device *dev = msm_obj->base.dev->dev; dma_map_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0); } static void sync_for_cpu(struct msm_gem_object *msm_obj) { struct device *dev = msm_obj->base.dev->dev; dma_unmap_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0); } On platforms where the top-level DRM device uses IOMMU DMA ops or SWIOTLB, the second dma_map_sgtable() call in sync_for_device() overwrites sg_dma_address and sg_dma_len, leaking the first IOVA or bounce mapping, while put_pages() unmaps and frees the second range twice. With CONFIG_DMA_API_DEBUG enabled, this also triggers overlapping mapping and double unmap warnings. Should sync_for_device() and sync_for_cpu() use dma_sync_sgtable_for_device() and dma_sync_sgtable_for_cpu() (or fold the CPU sync attribute into the map and unmap calls in get_pages() and put_pages()) instead of mapping and unmapping msm_obj->sgt a second time? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=2
