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

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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>
This commit is contained in:
Ming Lei 2019-11-02 16:02:15 +08:00 committed by Jens Axboe
parent 626fb735a4
commit 8962842ca5
1 changed files with 10 additions and 5 deletions
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15
block/blk-mq-sysfs.c
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@ -158,20 +158,25 @@ 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 = {