From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794047866; b=O4x4A/GQm1DK1DLg87jBrFiNaIxRZA4PEctGuJN2gAqAtML4VhuzLq92GR6px1HIGhCE LE8ZOtXwBu6tzm8QNJc/qbfbDNCtiIvUr4ZFf+opHL93CZcBES8b943aC+x/pmasdDhWR Y1z7iKPJLmDlOzgftgNU6JgeFXH6SBHEgF7wFN6teVz7/OGHlDflVu2juEIZ6yIug7/op x9tp4vk/rW7DXxmgzttYS0xxNi6JndcmjzbLeYDPvKqt8gaxjjiA7xjnt73/mmEk26Hmx ZcbYiKS8XmdJ0BsWgkJGjxradgjFfhUNawslRZYQdeITwEzSYMcX0VQ96onexk6Oqcw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047866; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=PnjYIYW4ax+wbQ1tu2auvxKCSSCEz2SFFMssqNlkvC8=; b=U4qj55n0J+9rY4JxADAmRwCffUH1afTsQJE69RPDu4ZksBxGPBKr24bOEsbcWnRTaH/a UvuZ16GiAbzpzfltBGv4uinf67lgHqNU6FTQ6EmEA1dveFOLupUB9pHT/9a70X+XXAfti 9cXmmVuSrAwNkWFCZ3beXb+SFSuX3ghQAfmhLRlMz0IX7nH/6Xe97cgIJIlGGFpFD8PnN AjDzm7FKskblSR5aSi40CTVs8Eu02HB/UnLzJRjb9q0C+ClkURnYLYvjMWyob7QytFL6J j++ex6440hpD4d70+I310Q+jAJkfqH845rLjGiDzhsRc+E9QBmQ45gtZvkJYxKwzDvQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=OO0K9OOi; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A6D7E606A326 for ; Sat, 7 Nov 2026 10:37:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=OO0K9OOi Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BC231F0089F; Sat, 7 Nov 2026 10:37:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047865; bh=PnjYIYW4ax+wbQ1tu2auvxKCSSCEz2SFFMssqNlkvC8=; h=From:To:Cc:Subject:Date; b=OO0K9OOiNXVfh2Gm6FvMWKKlk2bbJBoOAyuLAQPIknpONZ/HMimsnuP8qOEjbd+73 1Uk61InZR0iMZOdMikIzYPmceN/xBwUf9TQa8Jl/OGN36Cg15hYbGv4wwQr5fiI4ib EHnY0Qr2NOoQAB66nBSBeAH5SkS+ZgL2wlGkM0Jp4fxqbhOtIVfwaIO8RmI2JyfMaI 7L/GwD/IOZZXP4GVTBYq/T+qsaCBzGt0CdPi01QF1J5OEG0J8SfMMDaAu7Fft92noM WhKSGknukq1gi9DWE9vO2T/st1TQVyoH5/I8MUz39pNYOsa/PDVYx8CvKTzkelitpJ F6dZWserlhedA== From: Sasha Levin To: bsdhenrymartin@gmail.com, felix.kuehling@amd.com, alexander.deucher@amd.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] drm/amdkfd: fix doorbell allocation race creating duplicate allocations" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:37:44 -0500 Message-ID: <20261107053743-failed-6.6-bebad4505094@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x bebad45050945a3d668d6701fb77ae2571c5d44b # git commit -s git send-email --to '' --in-reply-to '20261107053743-failed-6.6-bebad4505094@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From bebad45050945a3d668d6701fb77ae2571c5d44b Mon Sep 17 00:00:00 2001 From: Henry Martin Date: Sat, 10 Oct 2026 11:02:30 +0800 Subject: [PATCH] drm/amdkfd: fix doorbell allocation race creating duplicate allocations The check-and-allocate sequence on pdd->qpd.proc_doorbells is lockless at every call site of kfd_alloc_process_doorbells(): kfd_get_process_doorbells() (mmap of /dev/kfd), kfd_ioctl_create_queue() and the CRIU restore path each test the pointer under different locking (or none), so two racing threads can both observe NULL and each allocate a doorbell BO and bitmap, orphaning one allocation and handing the two mappings different backing pages. Move the serialization into kfd_alloc_process_doorbells() itself, using a new per-process-device mutex so all three call sites are covered regardless of their own locking. The device-global kfd->doorbell_mutex is not suitable here: it is acquired under dqm->lock on the kernel-doorbell path (start_cpsch() -> pm_init() -> kq_initialize() -> kfd_get_kernel_doorbell()), so holding it across the sleeping allocations above would create a lock-ordering inversion with dqm->lock via TTM eviction, and it would also serialize doorbell setup of unrelated processes behind a device-wide lock for per-process state. This issue was discovered by Tencent CodeBuddy Security. v3 (Felix Kuehling): - Removed unlocked check in kfd_get_process_doorbell flagged as problematic by Sashiko Bot. Fall back to the locked check inside kfd_alloc_process_doorbells - Added missing mutex_destroy v4 (Felix Kuehling): - Removed unlocked checks around other kfd_alloc_process_doorbells calls Fixes: 16f0013157bf ("drm/amdkfd: Allocate doorbells only when needed") Signed-off-by: Henry Martin Signed-off-by: Felix Kuehling Reviewed-by: Felix Kuehling Signed-off-by: Alex Deucher (cherry picked from commit 4e27ba5ad5f76932d4f6cbacd25c81c2dd40ec4a) Cc: stable@vger.kernel.org --- drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 18 +++++++----------- drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c | 23 +++++++++++++++++------ drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 3 +++ drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 ++ 4 files changed, 29 insertions(+), 17 deletions(-) diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c index 344da6c0e96ad..3081d9aaf053a 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c @@ -427,12 +427,10 @@ static int kfd_ioctl_create_queue(struct file *filep, struct kfd_process *p, } } - if (!pdd->qpd.proc_doorbells) { - err = kfd_alloc_process_doorbells(dev->kfd, pdd); - if (err) { - pr_debug("failed to allocate process doorbells\n"); - goto err_bind_process; - } + err = kfd_alloc_process_doorbells(dev->kfd, pdd); + if (err) { + pr_debug("failed to allocate process doorbells\n"); + goto err_bind_process; } err = kfd_queue_acquire_buffers(pdd, &q_properties); @@ -2455,11 +2453,9 @@ static int criu_restore_devices(struct kfd_process *p, goto exit; } - if (!pdd->qpd.proc_doorbells) { - ret = kfd_alloc_process_doorbells(dev->kfd, pdd); - if (ret) - goto exit; - } + ret = kfd_alloc_process_doorbells(dev->kfd, pdd); + if (ret) + goto exit; } /* diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c b/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c index fdcf7f2d1b5b4..6af268a031f22 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c @@ -239,11 +239,9 @@ phys_addr_t kfd_get_process_doorbells(struct kfd_process_device *pdd) struct amdgpu_device *adev = pdd->dev->adev; uint32_t first_db_index; - if (!pdd->qpd.proc_doorbells) { - if (kfd_alloc_process_doorbells(pdd->dev->kfd, pdd)) - /* phys_addr_t 0 is error */ - return 0; - } + if (kfd_alloc_process_doorbells(pdd->dev->kfd, pdd)) + /* phys_addr_t 0 is error */ + return 0; first_db_index = amdgpu_doorbell_index_on_bar(adev, pdd->qpd.proc_doorbells, @@ -257,12 +255,21 @@ int kfd_alloc_process_doorbells(struct kfd_dev *kfd, struct kfd_process_device * int r; struct qcm_process_device *qpd = &pdd->qpd; + mutex_lock(&pdd->doorbell_mutex); + + /* Another thread may have won the check-and-allocate race */ + if (qpd->proc_doorbells) { + mutex_unlock(&pdd->doorbell_mutex); + return 0; + } + /* Allocate bitmap for dynamic doorbell allocation */ qpd->doorbell_bitmap = bitmap_zalloc(KFD_MAX_NUM_OF_QUEUES_PER_PROCESS, GFP_KERNEL); if (!qpd->doorbell_bitmap) { DRM_ERROR("Failed to allocate process doorbell bitmap\n"); - return -ENOMEM; + r = -ENOMEM; + goto unlock; } r = init_doorbell_bitmap(&pdd->qpd, kfd); @@ -284,11 +291,15 @@ int kfd_alloc_process_doorbells(struct kfd_dev *kfd, struct kfd_process_device * DRM_ERROR("Failed to allocate process doorbells\n"); goto err; } + + mutex_unlock(&pdd->doorbell_mutex); return 0; err: bitmap_free(qpd->doorbell_bitmap); qpd->doorbell_bitmap = NULL; +unlock: + mutex_unlock(&pdd->doorbell_mutex); return r; } diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h index b9a31489b1c89..e102086ac49a8 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h +++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h @@ -784,6 +784,9 @@ struct kfd_process_device { /* per-process-per device QCM data structure */ struct qcm_process_device qpd; + /* Serializes process doorbell allocation for this device */ + struct mutex doorbell_mutex; + /*Apertures*/ uint64_t lds_base; uint64_t lds_limit; diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c index 226f52626e849..51b0df4984945 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c @@ -1233,6 +1233,7 @@ static void kfd_process_destroy_pdds(struct kfd_process *p) } atomic_dec(&pdd->dev->kfd->kfd_processes_count); + mutex_destroy(&pdd->doorbell_mutex); kfree(pdd); p->pdds[i] = NULL; @@ -1802,6 +1803,7 @@ struct kfd_process_device *kfd_create_process_device_data(struct kfd_node *dev, pdd->dev = dev; INIT_LIST_HEAD(&pdd->qpd.queues_list); INIT_LIST_HEAD(&pdd->qpd.priv_queue_list); + mutex_init(&pdd->doorbell_mutex); pdd->qpd.dqm = dev->dqm; pdd->qpd.pqm = &p->pqm; pdd->qpd.evicted = 0; -- 2.53.0