From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B5186331200; Fri, 7 Aug 2026 14:56:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114605; cv=none; b=go8X83J46hzTNC7igDn8JZ3G7b7Z50SwaWwQCvJgN7lZUby/NgFe3yrDRe3mUjxQCYtTnsTeAVHRaVGEzeUSlZ8ux09+u7oYxKSxpFHET1/ZwUdJNiyrfglSrZhU2ViUnQ13LdZgqQy7oexwD1fSq865P5UFTrIugmDEO2qFI5A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114605; c=relaxed/simple; bh=FBFfdg1wM/87JkVagGnp/qYZ00IAh8DkzFjZ6xfjSuU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WQQ0tguhxqIk5un33e7A126N2yfrQczD07XHAx6E7Ceqg2l2e7nVztrUqekqclw5oSCVevgZGw+sW1WaMZtGvwjmNMeChhUgS8s21W98aMKpmKI/VbaGGACPiawO/++FA17vA25RzgRkmrVOOvAN6tKuhmbPo35fzhTXD3a7DE8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f0JFGxXy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f0JFGxXy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83ADA1F00A3A; Fri, 7 Aug 2026 14:56:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786114599; bh=9grP+0tUYTb8N5dGEDO/TufrwLkmPbYT8882vkCbwJ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=f0JFGxXyIHX33XwZFJl64iW9Z9925NUsJUUlGWVGvKAKmxGS30XwT0QdKsieu8ejg cSOqBcEbvQt/SD1dyJlgICKfL/Ono+bzctRY4gZWu8qMXiQwxuSKP3YuXBP4qigtQL YGmuGO6fOZCcVyXjRmiGCF6IKTFH+1C7KHFqAy3Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Thomas Hellstrom , Christian Konig , Matthew Auld , Nitin Gote , Sasha Levin Subject: [PATCH 6.12 321/337] drm/xe: Hold a dma-buf reference for imported BOs Date: Fri, 7 Aug 2026 16:38:44 +0200 Message-ID: <20260807143425.492590903@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143418.516897842@linuxfoundation.org> References: <20260807143418.516897842@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nitin Gote [ Upstream commit 62775525a27c3b0d56382e08ba81ee2d322058b6 ] An imported dma-buf BO is created as a ttm_bo_type_sg BO whose reservation object is the exporter's dma_buf->resv. The importer, however, only takes a dma-buf reference after a successful dma_buf_dynamic_attach(). Until then nothing keeps the exporter alive, so if the exporter is freed while the BO still references its resv, a later access to that resv is a use-after-free: Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b9c Workqueue: ttm ttm_bo_delayed_delete [ttm] RIP: 0010:mutex_can_spin_on_owner+0x3f/0xc0 This can be reached on two paths: - dma_buf_dynamic_attach() fails, or - ttm_bo_init_reserved() fails during BO creation. In both cases the BO already has bo->base.resv pointing at the exporter resv, and sg BOs are always torn down via ttm_bo_delayed_delete(), which locks bo->base.resv asynchronously - potentially after the exporter has been freed. Take the dma-buf reference in xe_bo_init_locked(), before ttm_bo_init_reserved(), so it also covers a creation failure there, and release it in xe_ttm_bo_destroy(). The reference is held for the whole BO lifetime, keeping the shared resv alive on every path. v2: - Reworked the fix to avoid creating the imported sg BO before dma_buf_dynamic_attach() succeeds. - Attach with importer_priv == NULL and make invalidate_mappings ignore incomplete imports. v3: - Dropped the xe-side reordering approach since importer_priv must be valid when dma_buf_dynamic_attach() publishes the attachment. - Per Christian's suggestion on the v1 thread, keyed the check on import_attach rather than removing the sg guard entirely. - Fixes both xe and amdgpu in a single TTM patch. v4: - Moved import_attach check to after dma_resv_copy_fences() so fences are copied before returning for successful imports (Thomas). - Removed exporter-alive claim from commit message (Thomas). v5: - Add drm/xe patch to keep imported sg BOs off the LRU before attach succeeds; the TTM fix alone is not sufficient for xe if the BO is already LRU-visible. (Thomas) v4 patch: https://patchwork.freedesktop.org/patch/736663/?series=169129&rev=2 - Patch 1 (drm/ttm) carries Christian's Reviewed-by from v4. v6: - Reworked the fix based on Thomas' suggestion. Instead of the TTM resv individualization (v1-v5) plus the xe off-LRU/placement handling (v5), just hold a dma-buf reference for the imported BO lifetime so the shared resv can never be freed while the BO still references it. Single xe patch, no TTM change. (Thomas) - Take the reference in xe_bo_init_locked() before ttm_bo_init_reserved() so a TTM creation failure is covered too (Thomas). - Dropped the v5 series (drm/ttm + drm/xe off-LRU); the off-LRU approach also regressed in CI BAT via ttm_bo_pipeline_gutting() creating a ghost BO that outlived the exporter. Link to v5: https://patchwork.freedesktop.org/series/169984/ v7: - Move changelog above --- so it stays in the commit message. - Reorder changelog entries oldest-to-newest. (Thomas) Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8023 Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs") Cc: stable@vger.kernel.org Cc: Thomas Hellstrom Cc: Christian Konig Cc: Matthew Auld Suggested-by: Thomas Hellstrom Assisted-by: GitHub_Copilot:claude-sonnet-4.6 Reviewed-by: Thomas Hellström Signed-off-by: Nitin Gote Signed-off-by: Matthew Auld Link: https://patch.msgid.link/20260710191027.260160-2-nitin.r.gote@intel.com (cherry picked from commit 3516f3fae6be35642f8f06f8a218da6425c0306a) Signed-off-by: Thomas Hellström Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/xe/xe_bo.c | 17 +++++++++++++++-- drivers/gpu/drm/xe/xe_bo.h | 2 +- drivers/gpu/drm/xe/xe_bo_types.h | 2 ++ drivers/gpu/drm/xe/xe_dma_buf.c | 2 +- 4 files changed, 19 insertions(+), 4 deletions(-) --- a/drivers/gpu/drm/xe/xe_bo.c +++ b/drivers/gpu/drm/xe/xe_bo.c @@ -1131,6 +1131,8 @@ static void xe_ttm_bo_destroy(struct ttm if (bo->ttm.base.import_attach) drm_prime_gem_destroy(&bo->ttm.base, NULL); + if (bo->dma_buf) + dma_buf_put(bo->dma_buf); drm_gem_object_release(&bo->ttm.base); xe_assert(xe, list_empty(&ttm_bo->base.gpuva.list)); @@ -1292,7 +1294,7 @@ struct xe_bo *xe_bo_init_locked(struct x struct xe_tile *tile, struct dma_resv *resv, struct ttm_lru_bulk_move *bulk, size_t size, u16 cpu_caching, enum ttm_bo_type type, - u32 flags) + u32 flags, struct dma_buf *dma_buf) { struct ttm_operation_ctx ctx = { .interruptible = true, @@ -1377,6 +1379,17 @@ struct xe_bo *xe_bo_init_locked(struct x placement = (type == ttm_bo_type_sg || bo->flags & XE_BO_FLAG_DEFER_BACKING) ? &sys_placement : &bo->placement; + + /* + * For imported BOs, keep the exporter dma-buf alive for the BO + * lifetime. Taken before ttm_bo_init_reserved() to also cover a + * creation failure there. Released in xe_ttm_bo_destroy(). + */ + if (dma_buf) { + get_dma_buf(dma_buf); + bo->dma_buf = dma_buf; + } + err = ttm_bo_init_reserved(&xe->ttm, &bo->ttm, type, placement, alignment, &ctx, NULL, resv, xe_ttm_bo_destroy); @@ -1491,7 +1504,7 @@ __xe_bo_create_locked(struct xe_device * vm && !xe_vm_in_fault_mode(vm) && flags & XE_BO_FLAG_USER ? &vm->lru_bulk_move : NULL, size, - cpu_caching, type, flags); + cpu_caching, type, flags, NULL); if (IS_ERR(bo)) return bo; --- a/drivers/gpu/drm/xe/xe_bo.h +++ b/drivers/gpu/drm/xe/xe_bo.h @@ -84,7 +84,7 @@ struct xe_bo *xe_bo_init_locked(struct x struct xe_tile *tile, struct dma_resv *resv, struct ttm_lru_bulk_move *bulk, size_t size, u16 cpu_caching, enum ttm_bo_type type, - u32 flags); + u32 flags, struct dma_buf *dma_buf); struct xe_bo * xe_bo_create_locked_range(struct xe_device *xe, struct xe_tile *tile, struct xe_vm *vm, --- a/drivers/gpu/drm/xe/xe_bo_types.h +++ b/drivers/gpu/drm/xe/xe_bo_types.h @@ -30,6 +30,8 @@ struct xe_bo { struct ttm_buffer_object ttm; /** @size: Size of this buffer object */ size_t size; + /** @dma_buf: Imported dma-buf ref to keep its resv alive. */ + struct dma_buf *dma_buf; /** @flags: flags for this buffer object */ u32 flags; /** @vm: VM this BO is attached to, for extobj this will be NULL */ --- a/drivers/gpu/drm/xe/xe_dma_buf.c +++ b/drivers/gpu/drm/xe/xe_dma_buf.c @@ -214,7 +214,7 @@ xe_dma_buf_init_obj(struct drm_device *d dma_resv_lock(resv, NULL); bo = xe_bo_init_locked(xe, storage, NULL, resv, NULL, dma_buf->size, 0, /* Will require 1way or 2way for vm_bind */ - ttm_bo_type_sg, XE_BO_FLAG_SYSTEM); + ttm_bo_type_sg, XE_BO_FLAG_SYSTEM, dma_buf); if (IS_ERR(bo)) { ret = PTR_ERR(bo); goto error;