It is reported that sysfs buffer overflow can be triggered in case
of too many CPU cores(>841 on 4K PAGE_SIZE) when showing CPUs in
one hctx.
So use snprintf for avoiding the potential buffer overflow.
Cc: stable@xxxxxxxxxxxxxxx
Cc: Mark Ray <mark.ray@xxxxxxx>
Fixes: 676141e48af7("blk-mq: don't dump CPU -> hw queue map on driver load")
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq-sysfs.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index d6e1a9bd7131..e75f41a98415 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -164,22 +164,28 @@ static ssize_t blk_mq_hw_sysfs_nr_reserved_tags_show(struct blk_mq_hw_ctx *hctx,
return sprintf(page, "%u\n", hctx->tags->nr_reserved_tags);
}
+/* avoid overflow by too many CPU cores */
static ssize_t blk_mq_hw_sysfs_cpus_show(struct blk_mq_hw_ctx *hctx, char *page)
{
- unsigned int i, first = 1;
- ssize_t ret = 0;
-
- for_each_cpu(i, hctx->cpumask) {
- if (first)
- ret += sprintf(ret + page, "%u", i);
- else
- ret += sprintf(ret + page, ", %u", i);
-
- first = 0;
+ unsigned int cpu = cpumask_first(hctx->cpumask);
+ ssize_t len = snprintf(page, PAGE_SIZE - 1, "%u", cpu);
+ int last_len = len;
+
+ while ((cpu = cpumask_next(cpu, hctx->cpumask)) < nr_cpu_ids) {
+ int cur_len = snprintf(page + len, PAGE_SIZE - 1 - len,
+ ", %u", cpu);
+ if (cur_len >= PAGE_SIZE - 1 - len) {
+ len -= last_len;
+ len += snprintf(page + len, PAGE_SIZE - 1 - len,
+ "...");
+ break;
+ }
+ len += cur_len;
+ last_len = cur_len;
}
- ret += sprintf(ret + page, "\n");
- return ret;
+ len += snprintf(page + len, PAGE_SIZE - 1 - len, "\n");
+ return len;
}
static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_tags = {
--
2.20.1
