From mboxrd@z Thu Jan 1 00:00:00 1970 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 368502D2486; Tue, 14 Jul 2026 04:26:16 +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=1784003180; cv=none; b=jewHjCbaNORP2KKjgtFIRDEDnY0bRgUZuuMue81rtq7UuwcczNROXQITWOiX57TR/lQ6Y0uUd22loj8JHwhJdGuAPLNYoaLpx26DC6ipeBmOXlDRdnThceK9M48+9US3R8cCpEF0qTT+mKg7MnZrU6039SLCyeWgOp397QwY7zk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784003180; c=relaxed/simple; bh=wxps8hTg+YscitVJedix/uB/417pItT4x+EkS+yf41Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Qj6+BwpEYtksnLNseD7fZwpEk8AMgKUvGDo2N18h2Aqg3TYQPUvxrR1B0iuUuXS8rSjPHrHa00XOAgmm9CEk4+tfQ+mp5LjGZRMSFAKr0tMJV17/5hzCxFtvc1bbjT7Dlq4MjDoe8oD47RGgLald/HQETiCM9Sb0FvsljxYbUjk= 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 [172.19.163.170]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4gzmSm0mghzKHMMK; Tue, 14 Jul 2026 12:25:44 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 3FBD54056B; Tue, 14 Jul 2026 12:26:14 +0800 (CST) Received: from huaweicloud.com (unknown [10.50.85.155]) by APP1 (Coremail) with UTF8SMTPSA id cCh0CgBHWHRkulVq2zKnBA--.54416S11; Tue, 14 Jul 2026 12:26:14 +0800 (CST) From: Zizhi Wo To: axboe@kernel.dk, dlemoal@kernel.org, nilay@linux.ibm.com, kch@nvidia.com, johannes.thumshirn@wdc.com, kbusch@kernel.org, bvanassche@acm.org, linux-block@vger.kernel.org Cc: linux-kernel@vger.kernel.org, yangerkun@huawei.com, chengzhihao1@huawei.com, wozizhi@huawei.com Subject: [PATCH V5 7/9] null_blk: reject per-device queue resize for shared tag set Date: Tue, 14 Jul 2026 12:18:03 +0800 Message-ID: <20260714041805.1088702-8-wozizhi@huaweicloud.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260714041805.1088702-1-wozizhi@huaweicloud.com> References: <20260714041805.1088702-1-wozizhi@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:cCh0CgBHWHRkulVq2zKnBA--.54416S11 X-Coremail-Antispam: 1UD129KBjvJXoWxWF1xtF1xCryfAFW5AFyDAwb_yoW5tFyfpF WrKayFkr1kG3W8X3yj9w42gF43AF4kZFWfJryfJFy5u3ZFvr95Z34kAa1UWF48J3ykC3yS q3ZrZw4kKa4UJ3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPvb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUAV Cq3wA2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0 rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVW8JVW5JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267 AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIEc7Cj xVAFwI0_GcCE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrV C2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE 7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwACI402YVCY1x02628vn2kIc2xKxwCY1x0262 kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s02 6c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw 0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvE c7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67 AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuY vjxUF9NVUUUUU X-CM-SenderInfo: pzr2x6tkl6x35dzhxuhorxvhhfrp/ From: Zizhi Wo When shared_tags is enabled, null_setup_tagset() makes the device use the global tag_set, whose driver_data stays NULL. null_map_queues() therefore falls back to the module-wide g_submit_queues/g_poll_queues instead of any per-device value. Resizing submit_queues or poll_queues via configfs on such a device calls blk_mq_update_nr_hw_queues() on the shared set, shrinking set->nr_hw_queues. __blk_mq_realloc_hw_ctxs() only grows the q->queue_hw_ctx[] allocation, so on shrink it merely exits and NULLs the now-excess hctx slots. null_map_queues(), however, keeps mapping CPUs with the unchanged g_submit_queues/g_poll_queues, so mq_map[] ends up pointing at those NULLed hctx slots. blk_mq_map_swqueue() then dereferences the NULL hctx (hctx->cpumask), crashing the kernel: [ 460.218374] KASAN: null-ptr-deref in range [0x0000000000000098-0x000000000000009f] [ 460.219003] CPU: 24 UID: 0 PID: 1492 Comm: sh Not tainted 7.2.0-rc2+ #67 PREEMPT(full) [ 460.219792] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 [ 460.220452] RIP: 0010:blk_mq_map_swqueue+0x4db/0x1430 ...... [ 460.228977] Call Trace: [ 460.229175] [ 460.229354] blk_mq_update_nr_hw_queues+0xd49/0x11c0 [ 460.229779] ? __pfx_blk_mq_update_nr_hw_queues+0x10/0x10 [ 460.230200] nullb_update_nr_hw_queues+0x1a9/0x370 [null_blk] [ 460.230694] nullb_device_submit_queues_store+0xd9/0x170 [null_blk] [ 460.231190] ? __pfx_nullb_device_submit_queues_store+0x10/0x10 [null_blk] [ 460.231776] ? configfs_write_iter+0x35c/0x4e0 [ 460.232122] configfs_write_iter+0x286/0x4e0 [ 460.232460] vfs_write+0x52d/0xd00 [ 460.232779] ? __x64_sys_openat+0x108/0x1d0 [ 460.233106] ? __pfx_vfs_write+0x10/0x10 [ 460.233413] ? fdget_pos+0x1cf/0x4c0 [ 460.233745] ? fput_close+0x133/0x190 [ 460.234038] ? __pfx_expand_files+0x10/0x10 [ 460.234368] ksys_write+0xfc/0x1d0 Reproducer: modprobe null_blk shared_tags=1 submit_queues=64 poll_queues=1 mkdir /sys/kernel/config/nullb/dev echo 1 > /sys/kernel/config/nullb/dev/power echo 1 > /sys/kernel/config/nullb/dev/submit_queues A per-device resize of a shared tag set is meaningless anyway, so reject it with -EINVAL in nullb_update_nr_hw_queues() when the device is bound to the global tag_set. Fixes: 45919fbfe1c4 ("null_blk: Enable modifying 'submit_queues' after an instance has been configured") Suggested-by: Nilay Shroff Assisted-by: Claude-Code:GLM-5.2 Signed-off-by: Zizhi Wo --- drivers/block/null_blk/main.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index 249caaf6ce89..ad6dfed12464 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -382,6 +382,15 @@ static int nullb_update_nr_hw_queues(struct nullb_device *dev, if (!dev->nullb) return 0; + /* + * A shared tag_set is mapped via the module-wide queue counts, so a + * per-device resize is meaningless. On shrink it would also leave + * mq_map[] pointing at NULLed hctx slots, causing a NULL deref in + * blk_mq_map_swqueue(). Reject it. + */ + if (dev->shared_tags) + return -EINVAL; + /* * Make sure at least one submit queue exists. */ -- 2.52.0