On Wed, Mar 25, 2020 at 5:14 PM <glider@xxxxxxxxxx> wrote:
>
> In vprintk_store(), vscnprintf() may return an uninitialized text_len
> value if any of its arguments are uninitialized. In that case KMSAN will
> report one or more errors in vscnprintf() itself, but it doesn't make
> much sense to track that value further, as it may trigger more errors in
> printk. Instead, we explicitly mark it as initialized.
>
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
> To: Alexander Potapenko <glider@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> Cc: Petr Mladek <pmladek@xxxxxxxx>
> Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: Marco Elver <elver@xxxxxxxxxx>
> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Acked-by: Petr Mladek <pmladek@xxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> ---
>
> This patch was split from "kmsan: call KMSAN hooks where needed", as
> requested by Andrey Konovalov. Petr Mladek has previously acked the
> printk part of that patch, hence the Acked-by above.
>
> v4:
> - split this patch away
>
> Change-Id: Ibed60b0bdd25f8ae91acee5800b5328e78e0735a
> ---
> kernel/printk/printk.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index ad46062345452..4cadba3c1e68d 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1913,6 +1913,12 @@ int vprintk_store(int facility, int level,
> * prefix which might be passed-in as a parameter.
> */
> text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
> + /*
> + * If any of vscnprintf() arguments is uninitialized, KMSAN will report
> + * one or more errors and also probably mark text_len as uninitialized.
> + * Initialize |text_len| to prevent the errors from spreading further.
> + */
> + text_len = KMSAN_INIT_VALUE(text_len);
>
> /* mark and strip a trailing newline */
> if (text_len && text[text_len-1] == '\n') {
> --
> 2.25.1.696.g5e7596f4ac-goog
>
