Re: [PATCH 2/4] kcsan, debugfs: refactor set_report_filterlist_whitelist() to return a value

[Marco Elver]

On Wed, 25 Sept 2024 at 16:32, ran xiaokai <ranxiaokai627@xxxxxxx> wrote:
>
> From: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
>
> This is a preparation patch, when converted to rcu lock,
> set_report_filterlist_whitelist() may fail due to memory alloction,
> refactor it to return a value, so the error codes can be
> passed to the userspace.
>
> Signed-off-by: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
> ---
>  kernel/kcsan/debugfs.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
> index ed483987869e..30547507f497 100644
> --- a/kernel/kcsan/debugfs.c
> +++ b/kernel/kcsan/debugfs.c
> @@ -131,13 +131,14 @@ bool kcsan_skip_report_debugfs(unsigned long func_addr)
>         return ret;
>  }
>
> -static void set_report_filterlist_whitelist(bool whitelist)
> +static ssize_t set_report_filterlist_whitelist(bool whitelist)
>  {
>         unsigned long flags;
>
>         spin_lock_irqsave(&report_filterlist_lock, flags);
>         report_filterlist.whitelist = whitelist;
>         spin_unlock_irqrestore(&report_filterlist_lock, flags);
> +       return 0;
>  }
>
>  /* Returns 0 on success, error-code otherwise. */
> @@ -225,6 +226,7 @@ debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *o
>         char kbuf[KSYM_NAME_LEN];
>         char *arg;
>         const size_t read_len = min(count, sizeof(kbuf) - 1);
> +       ssize_t ret;

This may be uninitialized depending on the branch taken below.

>         if (copy_from_user(kbuf, buf, read_len))
>                 return -EFAULT;
> @@ -242,19 +244,19 @@ debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *o
>                         return -EINVAL;
>                 microbenchmark(iters);
>         } else if (!strcmp(arg, "whitelist")) {
> -               set_report_filterlist_whitelist(true);
> +               ret = set_report_filterlist_whitelist(true);
>         } else if (!strcmp(arg, "blacklist")) {
> -               set_report_filterlist_whitelist(false);
> +               ret = set_report_filterlist_whitelist(false);
>         } else if (arg[0] == '!') {
> -               ssize_t ret = insert_report_filterlist(&arg[1]);
> -
> -               if (ret < 0)
> -                       return ret;
> +               ret = insert_report_filterlist(&arg[1]);
>         } else {
>                 return -EINVAL;
>         }
>
> -       return count;
> +       if (ret < 0)
> +               return ret;
> +       else
> +               return count;
>  }
>
>  static const struct file_operations debugfs_ops =
> --
> 2.15.2
>