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authorMing Lei <ming.lei@redhat.com>2019-11-02 16:02:15 +0800
committerJens Axboe <axboe@kernel.dk>2019-11-02 08:02:21 -0600
commit8962842ca5abdcf98e22ab3b2b45a103f0408b95 (patch)
tree8c2587331bbd6da0d4a520af10c30a23b2a55f63
parent626fb735a43ddcb7b2c58c27cb03b098acc03339 (diff)
blk-mq: avoid sysfs buffer overflow with too many CPU cores
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>
-rw-r--r--block/blk-mq-sysfs.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 81a273b43329..4caa56d1bc85 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -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 = {