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 C509B341068 for ; Sat, 22 Aug 2026 15:36:02 +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=1787412964; cv=none; b=kveyUEpRLooUwV/CnaSPEnOd8gy8B+FEUOe7oHWqk3kPg/ZcYrIBBcbq3DYooNti7vJwiIxAOXsaB8favNL2x1ZmDS5nclMyUmyIE0KyVpx5OQc8Cc3/Ks5+03eT6Tp3LghILJ+aKgoLUgfGwJ0/U5wR+q3MXnelpUyuguj1BAQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787412964; c=relaxed/simple; bh=AzRsd/88X1EfLsmKCaNs2M7bR8ONKqg2uvl4WVVv/7M=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=WNUwAuNKot3pl0ab7XFbvQTY7dw48mwHygpVhBPZq1Dy3g10MlXwgf/hPkDGjRbsBc8DJwxewgRY+ClI3wDwTwLVuXR3OtkCwDvXCMW1oGkmxQj6RZ66br/7tKyZLyOFswIIm1rfncTwntTrehfJH8v48tl7uR11ymabUhX6zUk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lGG/n/6/; 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="lGG/n/6/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5610A1F000E9; Sat, 22 Aug 2026 15:36:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787412962; bh=EB0H5URWKYLSPytpVC20H2vIZMNiroxPN48OOqrw2pQ=; h=From:To:Cc:Subject:Date:Reply-To; b=lGG/n/6/RpITT161ecup8plrAiX7DQwV9jJ5pehL5+JK0dqxgyZLhZxsRdh+k9qPx UxGzO9GEk9yaTrV3R1WQRoKLG0bCUVV9kgMUyUvxRjiJyXVFCekr2VjEC2nAjdLEtX 0ymZ0uaG2tAQXmns9/4hcGjV0ZjCw50IDT86dx/A= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-74638: drm/v3d: Serialize the scheduler timeout handlers Date: Sat, 22 Aug 2026 17:32:02 +0200 Message-ID: <2026082223-CVE-2026-74638-bed1@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4366; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=Ta3kF4Nhvwa4gq8d4Nx488+kh03qA+4oaVLCuKycEV0=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmdB07/WnbpbKGJaOstacO6iybnvpeJtrOLyggaGbMLb jzZybi2I5aFQZCJQVZMkeXLNp6j+ysOKXoZ2p6GmcPKBDKEgYtTACZS/YlhwY0qqac3TrJePMB3 pctB+ep74fgd4gwLzvVwRPV9U+HWakl+1j7vTfC6j1q7AA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: drm/v3d: Serialize the scheduler timeout handlers V3D exposes several independent hardware queues (BIN, RENDER, TFU and CSD) but has only a single, global reset. A timeout on any one queue therefore has to stop, reset and restart the schedulers of every other queue as well. That makes concurrent timeout handlers unsafe. `reset_lock` was never able to make them safe, as a driver-side lock can only cover the driver's &drm_sched_backend_ops.timedout_job callback. The scheduler handles the timed out job and its pending list around that callback, outside of the driver's control, so a global reset triggered by one queue can still interfere with another queue that is in the middle of handling a timeout of its own. Consequently, if a reset happens in the CSD queue while a CL-intensive application is running, the global reset stops and restarts the CL queue's scheduler while that queue is handling a timeout of its own. As drm_sched_stop() and drm_sched_start() subtract and add the credits of every job sitting on the pending list of the scheduler they are called on, and as the CL queue's handler concurrently takes its job off that same list and puts it back, the stop and the start no longer see the same set of jobs. The CL queue is left with more credits in flight than its limit: [ 327.302739] ------------[ cut here ]------------ [ 327.302744] WARNING: CPU: 2 PID: 43 at drivers/gpu/drm/scheduler/sched_main.c:102 drm_sched_run_job_work+0x238/0x4d0 [gpu_sched] [ 327.302884] CPU: 2 UID: 0 PID: 43 Comm: kworker/u16:1 Not tainted 6.18.39-v8-16k+ #3 PREEMPT [ 327.302889] Hardware name: Raspberry Pi 5 Model B Rev 1.0 (DT) [ 327.302893] Workqueue: v3d_bin drm_sched_run_job_work [gpu_sched] [ 327.302984] Call trace: [ 327.302987] drm_sched_run_job_work+0x238/0x4d0 [gpu_sched] (P) [ 327.302997] process_scheduled_works+0x180/0x3d0 [ 327.303010] worker_thread+0x268/0x3e8 [ 327.303016] kthread+0x140/0x250 [ 327.303022] ret_from_fork+0x10/0x20 [ 327.303031] ---[ end trace 0000000000000000 ]--- >>From that point on, the credit count of the CL queue is broken, causing a complete GPU hang and UI freeze. The DRM scheduler already provides a mechanism to serialize the timeout handlers of different schedulers: an ordered workqueue passed as drm_sched_init()'s @timeout_wq parameter. By default, each scheduler queues its timeout work on the system workqueue, which runs the handlers concurrently. Give all of the queues a shared ordered workqueue instead, as recommended by the DRM scheduler documentation for hardware that has distinct queues but resets globally. The Linux kernel CVE team has assigned CVE-2026-74638 to this issue. Affected and fixed versions =========================== Fixed in 6.18.45 with commit 5884851a096d8afcdf91f0e542bac193035183a6 Fixed in 7.1.9 with commit c22a45817b9c92aa0391db60e2ed467c7e6027d7 Fixed in 7.2 with commit 4da94744707b27a3ae1197bdd7127da4505dc5b1 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-74638 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/gpu/drm/v3d/v3d_drv.h drivers/gpu/drm/v3d/v3d_sched.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/5884851a096d8afcdf91f0e542bac193035183a6 https://git.kernel.org/stable/c/c22a45817b9c92aa0391db60e2ed467c7e6027d7 https://git.kernel.org/stable/c/4da94744707b27a3ae1197bdd7127da4505dc5b1