| From e0cd1630650733d939dab67e1682b64087cdc5e9 Mon Sep 17 00:00:00 2001 |
| From: Ming Lei <ming.lei@redhat.com> |
| Date: Sat, 2 Nov 2019 16:02:15 +0800 |
| Subject: [PATCH] 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: 676141e48af7("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: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c |
| index d6e1a9bd7131..7389311e28f8 100644 |
| --- a/block/blk-mq-sysfs.c |
| +++ b/block/blk-mq-sysfs.c |
| @@ -166,20 +166,25 @@ 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 blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_tags = { |
| -- |
| 2.7.4 |
| |