From nobody Thu Oct 9 04:50:05 2025 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 A620830E82C for ; Fri, 20 Jun 2025 01:16:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750382190; cv=none; b=Ig8PNv4V2WiY2B5IifYpSejBd0uXzEDtARPyQGPJ6CngUeTSeaXpcVB3qxzvo3GHyBsr/XiHoG99R91B+79IfgpJs4A4BJX/d09ppZaW6o+/4ncfagDsvA3YGlxHZ7BN6AyDvqmxG5R5JGb7QCSVlsKLQQfOfOCztQjQOCm7tbg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750382190; c=relaxed/simple; bh=cqzhOGwh4NTn0xkY7QTwlU0d8k1K3qIX+nMfLUwU2Vc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=C7eqcdN8+ZUOrk1KJQNjKvjk1d6vU9hzhlYTygBn1Ug83Lm2yjEQA5mZZnDPTx5Ic8+hsIhYKSkoLl6RkjUqeTwZ1FEH+57J6Ipx0EfEqqfXkZaEe6osWefyCNiyphWe8rmbvhaHyRzZZvUEnMaHlJ3WsEDwq9a2zSuuGE1YPu4= 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=45.249.212.51 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 [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4bNfgs0hvQzYQvTD for ; Fri, 20 Jun 2025 09:16:25 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 0D3BC1A1773 for ; Fri, 20 Jun 2025 09:16:24 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgAni19ltlRoWzc7QA--.26982S4; Fri, 20 Jun 2025 09:16:23 +0800 (CST) From: Yu Kuai To: akpm@linux-foundation.org, tglx@linutronix.de, ming.lei@redhat.com, axboe@kernel.dk, john.g.garry@oracle.com 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 v3] lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly() Date: Fri, 20 Jun 2025 09:09:58 +0800 Message-Id: <20250620010958.1265984-1-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: gCh0CgAni19ltlRoWzc7QA--.26982S4 X-Coremail-Antispam: 1UD129KBjvJXoW7KFWrGr1UKF43JrWfuFyUJrb_yoW8KFWxpF 43Kr4YgFWkJF18Aw45Zw4Iqa1ftFnYqrn3G34Skas8XF4agw45XF9rAFy5JFyrCwsxGa1f Xayqyr43Kry0yaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9Y14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U 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(), and later ZERO_SIZE_PTR will be deferenced. 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 --- Changes in v3: - also fix the non-SMP version. Changes in v2: - check numgrps directly. lib/group_cpus.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/lib/group_cpus.c b/lib/group_cpus.c index ee272c4cefcc..18d43a406114 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 @@ -426,8 +429,12 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps) #else /* CONFIG_SMP */ struct cpumask *group_cpus_evenly(unsigned int numgrps) { - struct cpumask *masks =3D kcalloc(numgrps, sizeof(*masks), GFP_KERNEL); + struct cpumask *masks; =20 + if (numgrps =3D=3D 0) + return NULL; + + masks =3D kcalloc(numgrps, sizeof(*masks), GFP_KERNEL); if (!masks) return NULL; =20 --=20 2.39.2