3.16.82-rc1 review patch. If anyone has any objections, please let me know.
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From: Ming Lei ming.lei@redhat.com
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.
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: Ben Hutchings ben@decadent.org.uk --- 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 @@ -226,20 +226,25 @@ static ssize_t blk_mq_hw_sysfs_active_sh
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_ctx_sysfs_entry blk_mq_sysfs_dispatched = {