Re: [PATCH] signal: improve warning about using SI_TKILL in rt_[tg]sigqueueinfo

Oleg Nesterov
2015-03-19T13:02:44Z

On 03/19, Vladimir Davydov wrote:
>
> Sending SI_TKILL from rt_[tg]sigqueueinfo was deprecated, so now we
> issue a warning on the first attempt of doing it. We use WARN_ON_ONCE,
> which is not informative and, what is worse, taints the kernel, making
> the trinity syscall fuzzer complain false-positively from time to time.
>
> This patch therefore substitutes the WARN_ON_ONCE with a pr_warn_once.

Agreed.

but perhaps we can simply remove this warning at all?

> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
> ---
> kernel/signal.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index a390499943e4..3cbcd94457af 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2993,8 +2993,11 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
> */
> if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
> (task_pid_vnr(current) != pid)) {
> - /* We used to allow any < 0 si_code */
> - WARN_ON_ONCE(info->si_code < 0);
> + /* We used to allow SI_TKILL */
> + if (info->si_code == SI_TKILL)
> + pr_warn_once("%s (%d): Sending SI_TKILL from "
> + "rt_sigqueueinfo is deprecated\n",
> + current->comm, current->pid);
> return -EPERM;
> }
> info->si_signo = sig;
> @@ -3041,10 +3044,13 @@ static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
> /* Not even root can pretend to send signals from the kernel.
> * Nor can they impersonate a kill()/tgkill(), which adds source info.
> */
> - if (((info->si_code >= 0 || info->si_code == SI_TKILL)) &&
> + if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
> (task_pid_vnr(current) != pid)) {
> - /* We used to allow any < 0 si_code */
> - WARN_ON_ONCE(info->si_code < 0);
> + /* We used to allow SI_TKILL */
> + if (info->si_code == SI_TKILL)
> + pr_warn_once("%s (%d): Sending SI_TKILL from "
> + "rt_tgsigqueueinfo is deprecated\n",
> + current->comm, current->pid);
> return -EPERM;
> }
> info->si_signo = sig;
> --
> 1.7.10.4
>