From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EBC65C43458 for ; Fri, 10 Jul 2026 18:33:34 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 975CD10E219; Fri, 10 Jul 2026 18:33:34 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="AsM6Onxc"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.19]) by gabe.freedesktop.org (Postfix) with ESMTPS id 130C510E219 for ; Fri, 10 Jul 2026 18:33:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1783708414; x=1815244414; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=Rfy4qwT8r08woMWfxAU9OUwsLgNLjNW69XqNPLK5ykk=; b=AsM6OnxcNp2tezRQMl+wWM7zApMb7AsoQ2xkA3CbxTU7Q0ZQwlugJUaQ 6JN2lCd64d278IgDS1XYsFH2KB5m02HQBcZOVoNRJhvPjlp4M02V+3M+w aytMoPh3vQDHxWr5OacySD/nKrkzeFBW6zDd9jOfZo8dnB+aweTdlOFOs /8AbYbFw7ndENrHK5P7o98zLkfWf2UYuHaLQHm85xn1OB6mIrlb/2hdQ1 oNiax38f7LFJRR/QTrD4XexpsiSPKQJVSLkuk1FPdySwLtjKQAkBmx1Dg 8sGl5YmSOvjNRog97srfJHjAJs2CPIEtapcKUrClS3uIj82pw82BG5vbq A==; X-CSE-ConnectionGUID: CTYk3rFPRnyk+jX/sz/ARQ== X-CSE-MsgGUID: trDdDe5FRtW0WZS2TBaY7g== X-IronPort-AV: E=McAfee;i="6800,10657,11841"; a="83390838" X-IronPort-AV: E=Sophos;i="6.25,154,1779174000"; d="scan'208";a="83390838" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jul 2026 11:33:33 -0700 X-CSE-ConnectionGUID: iPIysde9QoyxRRaB9uBk5A== X-CSE-MsgGUID: UenBA1pwQ2q/81VOwNTX5A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,154,1779174000"; d="scan'208";a="254453107" Received: from nitin-super-server.iind.intel.com ([10.190.238.72]) by orviesa008.jf.intel.com with ESMTP; 10 Jul 2026 11:33:31 -0700 From: Nitin Gote To: intel-xe@lists.freedesktop.org Cc: Nitin Gote , stable@vger.kernel.org, Thomas Hellstrom , Christian Konig , Matthew Auld Subject: [PATCH] drm/xe: Hold a dma-buf reference for imported BOs Date: Sat, 11 Jul 2026 00:40:28 +0530 Message-ID: <20260710191027.260160-2-nitin.r.gote@intel.com> X-Mailer: git-send-email 2.50.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" 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 --- drivers/gpu/drm/xe/xe_bo.c | 24 ++++++++++++++++++++---- drivers/gpu/drm/xe/xe_bo.h | 3 ++- drivers/gpu/drm/xe/xe_bo_types.h | 2 ++ drivers/gpu/drm/xe/xe_dma_buf.c | 2 +- 4 files changed, 25 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c index 85e6d9a0f575..ae730bd6f4b2 100644 --- a/drivers/gpu/drm/xe/xe_bo.c +++ b/drivers/gpu/drm/xe/xe_bo.c @@ -1349,7 +1349,7 @@ int xe_bo_notifier_prepare_pinned(struct xe_bo *bo) backup = xe_bo_init_locked(xe, NULL, NULL, bo->ttm.base.resv, NULL, xe_bo_size(bo), DRM_XE_GEM_CPU_CACHING_WB, ttm_bo_type_kernel, XE_BO_FLAG_SYSTEM | XE_BO_FLAG_NEEDS_CPU_ACCESS | - XE_BO_FLAG_PINNED, &exec); + XE_BO_FLAG_PINNED, NULL, &exec); if (IS_ERR(backup)) { drm_exec_retry_on_contention(&exec); ret = PTR_ERR(backup); @@ -1490,7 +1490,7 @@ int xe_bo_evict_pinned(struct xe_bo *bo) xe_bo_size(bo), DRM_XE_GEM_CPU_CACHING_WB, ttm_bo_type_kernel, XE_BO_FLAG_SYSTEM | XE_BO_FLAG_NEEDS_CPU_ACCESS | - XE_BO_FLAG_PINNED, &exec); + XE_BO_FLAG_PINNED, NULL, &exec); if (IS_ERR(backup)) { drm_exec_retry_on_contention(&exec); ret = PTR_ERR(backup); @@ -1826,6 +1826,8 @@ static void xe_ttm_bo_destroy(struct ttm_buffer_object *ttm_bo) 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)); @@ -2283,6 +2285,8 @@ void xe_bo_free(struct xe_bo *bo) * @cpu_caching: The cpu caching used for system memory backing store. * @type: The TTM buffer object type. * @flags: XE_BO_FLAG_ flags. + * @dma_buf: The dma-buf to reference for the BO lifetime (imported BOs), + * or NULL. * @exec: The drm_exec transaction to use for exhaustive eviction. * * Initialize or create an xe buffer object. On failure, any allocated buffer @@ -2294,7 +2298,8 @@ struct xe_bo *xe_bo_init_locked(struct xe_device *xe, struct xe_bo *bo, 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, struct drm_exec *exec) + u32 flags, struct dma_buf *dma_buf, + struct drm_exec *exec) { struct ttm_operation_ctx ctx = { .interruptible = true, @@ -2383,6 +2388,17 @@ struct xe_bo *xe_bo_init_locked(struct xe_device *xe, struct xe_bo *bo, 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); @@ -2500,7 +2516,7 @@ __xe_bo_create_locked(struct xe_device *xe, vm && !xe_vm_in_fault_mode(vm) && flags & XE_BO_FLAG_USER ? &vm->lru_bulk_move : NULL, size, - cpu_caching, type, flags, exec); + cpu_caching, type, flags, NULL, exec); if (IS_ERR(bo)) return bo; diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h index 6340317f7d2e..7ae1d9ac0574 100644 --- a/drivers/gpu/drm/xe/xe_bo.h +++ b/drivers/gpu/drm/xe/xe_bo.h @@ -118,7 +118,8 @@ struct xe_bo *xe_bo_init_locked(struct xe_device *xe, struct xe_bo *bo, 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, struct drm_exec *exec); + u32 flags, struct dma_buf *dma_buf, + struct drm_exec *exec); struct xe_bo *xe_bo_create_locked(struct xe_device *xe, struct xe_tile *tile, struct xe_vm *vm, size_t size, enum ttm_bo_type type, u32 flags, diff --git a/drivers/gpu/drm/xe/xe_bo_types.h b/drivers/gpu/drm/xe/xe_bo_types.h index fcc63ae3f455..e45f24301050 100644 --- a/drivers/gpu/drm/xe/xe_bo_types.h +++ b/drivers/gpu/drm/xe/xe_bo_types.h @@ -36,6 +36,8 @@ struct xe_bo { struct xe_bo *backup_obj; /** @parent_obj: Ref to parent bo if this a backup_obj */ struct xe_bo *parent_obj; + /** @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 */ diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c index 8a920e58245c..bf0728838ead 100644 --- a/drivers/gpu/drm/xe/xe_dma_buf.c +++ b/drivers/gpu/drm/xe/xe_dma_buf.c @@ -302,7 +302,7 @@ xe_dma_buf_create_obj(struct drm_device *dev, struct dma_buf *dma_buf) bo = xe_bo_init_locked(xe, NULL, NULL, resv, NULL, dma_buf->size, 0, /* Will require 1way or 2way for vm_bind */ - ttm_bo_type_sg, XE_BO_FLAG_SYSTEM, &exec); + ttm_bo_type_sg, XE_BO_FLAG_SYSTEM, dma_buf, &exec); drm_exec_retry_on_contention(&exec); if (IS_ERR(bo)) { ret = PTR_ERR(bo); -- 2.50.1