From: Ming Lei <ming.lei@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Fixes: 676141e48af7("blk-mq: don't dump CPU -> hw queue map on driver load")
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/blk-mq-sysfs.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -145,20 +145,25 @@ static ssize_t blk_mq_hw_sysfs_nr_reserv
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[] = {
