Commit 317c80c6 authored Nov 02, 2019 by Ming Lei Committed by Greg Kroah-Hartman Dec 17, 2019

blk-mq: avoid sysfs buffer overflow with too many CPU cores



commit 8962842ca5abdcf98e22ab3b2b45a103f0408b95 upstream.

It is reported that sysfs buffer overflow can be triggered if the system
has too many CPU cores(>841 on 4K PAGE_SIZE) when showing CPUs of
hctx via /sys/block/$DEV/mq/$N/cpu_list.

Use snprintf to avoid the potential buffer overflow.

This version doesn't change the attribute format, and simply stops
showing CPU numbers if the buffer is going to overflow.

Cc: stable@vger.kernel.org
Fixes: 676141e4("blk-mq: don't dump CPU -> hw queue map on driver load")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent a12c768d

block/blk-mq-sysfs.c

+10 −5

Original line number	Diff line number	Diff line
		@@ -151,20 +151,25 @@ static ssize_t blk_mq_hw_sysfs_nr_reserved_tags_show(struct blk_mq_hw_ctx *hctx,

		static ssize_t blk_mq_hw_sysfs_cpus_show(struct blk_mq_hw_ctx hctx, char page)
		{
		const size_t size = PAGE_SIZE - 1;
		unsigned int i, first = 1;
		ssize_t ret = 0;
		int ret = 0, pos = 0;

		for_each_cpu(i, hctx->cpumask) {
		if (first)
		ret += sprintf(ret + page, "%u", i);
		ret = snprintf(pos + page, size - pos, "%u", i);
		else
		ret += sprintf(ret + page, ", %u", i);
		ret = snprintf(pos + page, size - pos, ", %u", i);

		if (ret >= size - pos)
		break;

		first = 0;
		pos += ret;
		}

		ret += sprintf(ret + page, "\n");
		return ret;
		ret = snprintf(pos + page, size - pos, "\n");
		return pos + ret;
		}

		static struct attribute *default_ctx_attrs[] = {