On 2019/1/30 5:29 下午, Geliang Tang wrote:
> This patch uses kmemdup_nul to create a NUL-terminated string from
> dc->sb.label. This is better than open coding it.
>
> With this, we can move env[2] initialization into env[] array to make
> code more elegant.
>
> Signed-off-by: Geliang Tang <geliangtang@xxxxxxxxx>
Hi Geliang,
In general I am OK with your idea. But I feel there might be some
regression with your change. I comment your patch in line, correct me if
I am wrong.
> ---
> drivers/md/bcache/super.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 4dee119c3664..84ab241c8516 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -906,21 +906,18 @@ static int cached_dev_status_update(void *arg)
> void bch_cached_dev_run(struct cached_dev *dc)
> {
> struct bcache_device *d = &dc->disk;
> - char buf[SB_LABEL_SIZE + 1];
> + char *buf = kmemdup_nul(dc->sb.label, SB_LABEL_SIZE, GFP_KERNEL);
If kdumdup_null() is failed, buf will be NULL.
> char *env[] = {
> "DRIVER=bcache",
> kasprintf(GFP_KERNEL, "CACHED_UUID=%pU", dc->sb.uuid),
> - NULL,
> + kasprintf(GFP_KERNEL, "CACHED_LABEL=%s", buf ? : ""),
If buf is NULL, env[2] here is pointed to "" which is allocated in
read-only data segment, and not a dynamic memory.
> NULL,
> };
>
> - memcpy(buf, dc->sb.label, SB_LABEL_SIZE);
> - buf[SB_LABEL_SIZE] = '\0';
> - env[2] = kasprintf(GFP_KERNEL, "CACHED_LABEL=%s", buf);
> -
> if (atomic_xchg(&dc->running, 1)) {
> kfree(env[1]);
> kfree(env[2]);
Then kfree() here will try to release a read-only memory segment. I
guess this is problematic.
> + kfree(buf);
> return;
> }
>
> @@ -944,6 +941,7 @@ void bch_cached_dev_run(struct cached_dev *dc)
> kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env);
> kfree(env[1]);
> kfree(env[2]);
Same problem might happen here for env[2].
> + kfree(buf);
>
> if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") ||
> sysfs_create_link(&disk_to_dev(d->disk)->kobj, &d->kobj, "bcache"))
>
--
Coly Li
