From nobody Thu Oct 9 07:03:10 2025 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (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 433FA25D8FA for ; Thu, 19 Jun 2025 13:33:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750340006; cv=none; b=brXGVYX/ayZLsuO10KdyIM9YVJWn6Mkpx8QOpwEXjwtHJt9vzOHrM2vPueNf9iOio+YgABcOquCSfCMux8xIakrxS0+uFaJjkfNaJXMI/TrHjzC9uKNjlFZRDgrTlKaIdg/cq8RmZocABJh42oqEokie6SQICfJWjh3DufJ3lQA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750340006; c=relaxed/simple; bh=4jFqluJG20UjTfdnDhk02sGkpiGko5EtGtm1OQXooh8=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=sRbsME7sGHll+W8kgNTYS+gm7gwLlt+KZeP3JDFdMuhXzocW0cbyqXIo4sMy6D0i7qcUB3KnU32Y8gOk3NJS+r30Z2yfHGLEIotfyOP5IlS5QCpZc3jBMYUlk33wcuO2dXwStej981pSk1KbfE0Jw8JIMeGV8v8ApM2zcTVrDjY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4bNM4c6dqTzKHMlB for ; Thu, 19 Jun 2025 21:33:20 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 493EA1A08FF for ; Thu, 19 Jun 2025 21:33:19 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgC3Gl+dEVRoTukHQA--.57071S4; Thu, 19 Jun 2025 21:33:19 +0800 (CST) From: Yu Kuai To: tglx@linutronix.de, akpm@linux-foundation.org, john.g.garry@oracle.com, ming.lei@redhat.com, axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com Subject: [PATCH v2] lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly() Date: Thu, 19 Jun 2025 21:26:55 +0800 Message-Id: <20250619132655.3318883-1-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: gCh0CgC3Gl+dEVRoTukHQA--.57071S4 X-Coremail-Antispam: 1UD129KBjvJXoW7KFWrGr1UKF43JrWfuFyUJrb_yoW8Zr45pF 45Kw4YkFykGF18Aw45Zw4Ig3WFgFnYvF1fGrWIkrn8XF4aqw45Xr93AFW5JrW8CwsxGa1f Xayvyr45tryjyaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9Y14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26F1j6w1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lFIxGxcIEc7CjxVA2 Y2ka0xkIwI1lc7CjxVAaw2AFwI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x 0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2 zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF 4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWU CwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCT nIWIevJa73UjIFyTuYvjfUonmRUUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ Content-Type: text/plain; charset="utf-8" From: Yu Kuai While testing null_blk with configfs, echo 0 > poll_queues will trigger following panic: BUG: kernel NULL pointer dereference, address: 0000000000000010 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 27 UID: 0 PID: 920 Comm: bash Not tainted 6.15.0-02023-gadbdb95c8696-d= irty #1238 PREEMPT(undef) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 0= 4/01/2014 RIP: 0010:__bitmap_or+0x48/0x70 Call Trace: __group_cpus_evenly+0x822/0x8c0 group_cpus_evenly+0x2d9/0x490 blk_mq_map_queues+0x1e/0x110 null_map_queues+0xc9/0x170 [null_blk] blk_mq_update_queue_map+0xdb/0x160 blk_mq_update_nr_hw_queues+0x22b/0x560 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk] nullb_device_poll_queues_store+0xa4/0x130 [null_blk] configfs_write_iter+0x109/0x1d0 vfs_write+0x26e/0x6f0 ksys_write+0x79/0x180 __x64_sys_write+0x1d/0x30 x64_sys_call+0x45c4/0x45f0 do_syscall_64+0xa5/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e Root cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from kcalloc(), then __group_cpus_evenly() will deference the ZERO_SIZE_PTR. Fix the problem by checking numgrps first in group_cpus_evenly(), and return NULL directly if numgrps is zero. Fixes: 6a6dcae8f486 ("blk-mq: Build default queue map via group_cpus_evenly= ()") Signed-off-by: Yu Kuai Reviewed-by: Jens Axboe Reviewed-by: Ming Lei --- Changes in v2: - check numgrps directly. lib/group_cpus.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/group_cpus.c b/lib/group_cpus.c index ee272c4cefcc..d68407e3601e 100644 --- a/lib/group_cpus.c +++ b/lib/group_cpus.c @@ -352,6 +352,9 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps) int ret =3D -ENOMEM; struct cpumask *masks =3D NULL; =20 + if (numgrps =3D=3D 0) + return NULL; + if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL)) return NULL; =20 --=20 2.39.2