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Tue, 01 Sep 2026 18:27:17 -0700 (PDT) Received: from MalHyuk.localdomain ([211.201.32.99]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39ae0f2a315sm2443563a91.8.2026.09.01.18.27.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 18:27:17 -0700 (PDT) From: "Jonghyuk Kim(MalHyuk)" To: Min Ma , Lizhi Hou , Oded Gabbay Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] accel/amdxdna: RCU-free the scheduler-containing hwctx private Date: Wed, 2 Sep 2026 10:27:12 +0900 Message-ID: <20260902012712.880520-1-malhyuk97@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit struct amdxdna_hwctx_priv embeds a struct drm_gpu_scheduler (priv->sched). aie2_hwctx_fini() calls drm_sched_fini(&priv->sched) and then frees the whole object with plain kfree(hwctx->priv). Every drm_sched_fence produced by that scheduler stores fence->sched = &priv->sched, and drm_sched_fence_get_timeline_name() returns fence->sched->name. The scheduler fence ops keep a .release callback, so the fence is not ops-detached on signalling: a finished fence that userspace still holds (exported via drm_syncobj / sync_file) keeps pointing at priv->sched after the hwctx is torn down. A later get_timeline_name() -- reachable unprivileged through SYNC_IOC_FILE_INFO on the exported sync_file -- then dereferences priv->sched->name in freed slab memory (KASAN slab-use-after-free read). This is the amdxdna instance of the dma-fence lifetime contract: the exporter must keep the driver data backing a fence alive for an RCU grace period after the fence is signalled, so a concurrent rcu_read_lock'd dma_fence_timeline_name() cannot observe freed memory. aie2_hwctx_fini() already waits for all submitted jobs to complete/cancel, so the fences are signalled by teardown time; only the teardown race window remains, which an RCU-delayed free closes. Free the scheduler-containing private with kfree_rcu() instead of kfree(). The init-failure unwind keeps plain kfree(): no job has been submitted there, so no drm_sched_fence has been exported. Fixes: be462c97b7df ("accel/amdxdna: Add hardware context") Cc: stable@vger.kernel.org Signed-off-by: Jonghyuk Kim(MalHyuk) --- drivers/accel/amdxdna/aie2_ctx.c | 2 +- drivers/accel/amdxdna/aie2_pci.h | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/accel/amdxdna/aie2_ctx.c b/drivers/accel/amdxdna/aie2_ctx.c index 4b3a62aa8798..26bd6e001792 100644 --- a/drivers/accel/amdxdna/aie2_ctx.c +++ b/drivers/accel/amdxdna/aie2_ctx.c @@ -842,7 +842,7 @@ void aie2_hwctx_fini(struct amdxdna_hwctx *hwctx) mutex_destroy(&hwctx->priv->io_lock); kfree(hwctx->col_list); - kfree(hwctx->priv); + kfree_rcu(hwctx->priv, rcu); kfree(hwctx->cus); } diff --git a/drivers/accel/amdxdna/aie2_pci.h b/drivers/accel/amdxdna/aie2_pci.h index ea1dac106400..e08b8f64328c 100644 --- a/drivers/accel/amdxdna/aie2_pci.h +++ b/drivers/accel/amdxdna/aie2_pci.h @@ -107,6 +107,8 @@ struct amdxdna_hwctx_priv { struct amdxdna_gem_obj *heap; void *mbox_chann; + struct rcu_head rcu; + struct drm_gpu_scheduler sched; struct drm_sched_entity entity;