[PATCH 1/1] signals: introduce send_sigkill() helper
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From: Oleg Nesterov on 9 Jun 2010 21:10 Cleanup, no functional changes. There are a lot of buggy SIGKILL users in kernel. For example, almost every force_sig(SIGKILL) is wrong. force_sig() is not safe, it assumes that the task has the valid ->sighand, and in general it should be used only for synchronous signals. send_sig(SIGKILL, p, 1) or send_xxx(SEND_SIG_FORCED/SEND_SIG_PRIV) is not right too but this is not immediately obvious. The only way to correctly send SIGKILL is send_sig_info(SEND_SIG_NOINFO) but we do not want to use this directly, because we can optimize this case later. For example, zap_pid_ns_processes() allocates sigqueue for each process in namespace, this is unneeded. Introduce the trivial send_sigkill() helper on top of send_sig_info() and change zap_pid_ns_processes() as an example. Note: we need more cleanups here, this is only the first change. Signed-off-by: Oleg Nesterov <oleg(a)redhat.com> --- include/linux/sched.h | 9 +++++++++ kernel/pid_namespace.c | 8 +------- 2 files changed, 10 insertions(+), 7 deletions(-) --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2053,6 +2053,15 @@ static inline int kill_cad_pid(int sig, #define SEND_SIG_PRIV ((struct siginfo *) 1) #define SEND_SIG_FORCED ((struct siginfo *) 2) +static inline int send_sigkill(struct task_struct * p) +{ + /* + * Kills any user-space task, even SIGNAL_UNKILLABLE. + * We use SEND_SIG_NOINFO to make si_fromuser() true. + */ + return send_sig_info(SIGKILL, SEND_SIG_NOINFO, p); +} + /* * True if we are on the alternate signal stack. */ --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -160,15 +160,9 @@ void zap_pid_ns_processes(struct pid_nam nr = next_pidmap(pid_ns, 1); while (nr > 0) { rcu_read_lock(); - - /* - * Any nested-container's init processes won't ignore the - * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser(). - */ task = pid_task(find_vpid(nr), PIDTYPE_PID); if (task) - send_sig_info(SIGKILL, SEND_SIG_NOINFO, task); - + send_sigkill(task); rcu_read_unlock(); nr = next_pidmap(pid_ns, nr); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |