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Date: Thu, 18 Sep 2008 22:20:15 +0200
From: Marcin Slusarz <marcin.slusarz@...il.com>
To: Thomas Jarosch <thomas.jarosch@...ra2net.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: RFC: [patch] log fatal signals like SIGSEGV
On Thu, Sep 18, 2008 at 12:10:39PM +0200, Thomas Jarosch wrote:
> > It looks much better now. But I don't think it will go in as is.
> > Maybe you can disable it by default and create a sysctl switch?
>
> Thinking about it some more, I've added a "signal-log-level" sysctl var
> including documentation. The patch applies nicely to 2.6.26 and 2.6 HEAD.
>
> The idea is to default to log level 1 and log fatal signals only.
> Log output should be close to zero during normal system operation.
>
> There is a bit of a naming clash with "print-fatal-signals", though that
> should be called "debug-fatal-signals" because of all the register dumps etc.
> I don't want to rename it as it would unnecessarily cause issues
> and it's debug-only (Documentation/kernel-parameters.txt) anyway.
>
> Enjoy.
>
> ------------------------------------------------------
> From: Thomas Jarosch <thomas.jarosch@...ra2net.com>
>
> Log signals like SIGSEGV, SIGILL, SIGBUS or SIGFPE to aid tracing
> of obscure problems. Also logs the sender of the signal.
>
> The log message looks like this:
> "kernel: signal 9 sent to freezed[2634] uid:100,
> parent init[1] uid:0 by bash[3168] uid:0, parent sshd[3164] uid:0"
>
> You can control the degree of logging via sysctl: "signal-log-level"
> 0 - Signal logging disabled
> 1 - Log SIGSEGV, SIGILL, SIGBUS and SIGPFE (default)
^^^^^^
> 2 - Log SIGKILL and SIGABRT and all signals from log level 1
> 3 or higher: Log all signals
>
> The printing code is based on grsecurity's signal logger.
>
> Signed-off-by: Thomas Jarosch <thomas.jarosch@...ra2net.com>
> Signed-off-by: Gerd v. Egidy <gve@...ra2net.com>
>
> diff -u -r -p linux-2.6.26.vanilla/kernel/signal.c linux-2.6.26/kernel/signal.c
> --- linux-2.6.26.vanilla/kernel/signal.c Tue Sep 16 13:45:34 2008
> +++ linux-2.6.26/kernel/signal.c Thu Sep 18 10:43:27 2008
> @@ -796,6 +796,35 @@ static void complete_signal(int sig, str
> return;
> }
>
> +int signal_log_level __read_mostly = 1;
> +
> +static void log_signal(const int sig, const struct task_struct *t)
> +{
> + bool log_signal = false;
> +
> + if(signal_log_level >= 1 && (sig == SIGSEGV || sig == SIGILL
> + || sig == SIGBUS || sig == SIGFPE))
> + log_signal = true;
> + else if (signal_log_level >= 2 && (sig == SIGKILL || sig == SIGABRT))
> + log_signal = true;
> + else if (signal_log_level >= 3)
> + log_signal = true;
> +
> + if (!log_signal)
> + return;
> +
> + if (printk_ratelimit()) {
> + /* Don't lock "tasklist_lock" here as it's already locked by "siglock" */
> + printk(KERN_WARNING "signal %d sent to %.30s[%d] uid:%u, "
> + "parent %.30s[%d] uid:%u by %.30s[%d] uid:%u, "
> + "parent %.30s[%d] uid:%u\n", sig, t->comm,
> + t->pid, t->uid, t->parent->comm, t->parent->pid,
> + t->parent->uid, current->comm, current->pid,
> + current->uid, current->parent->comm,
> + current->parent->pid, current->parent->uid);
> + }
> +}
> +
> static inline int legacy_queue(struct sigpending *signals, int sig)
> {
> return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
> @@ -810,6 +839,8 @@ static int send_signal(int sig, struct s
> assert_spin_locked(&t->sighand->siglock);
> if (!prepare_signal(sig, t))
> return 0;
> +
> + log_signal(sig, t);
>
> pending = group ? &t->signal->shared_pending : &t->pending;
> /*
> diff -u -r -p linux-2.6.26.vanilla/kernel/sysctl.c linux-2.6.26/kernel/sysctl.c
> --- linux-2.6.26.vanilla/kernel/sysctl.c Sun Jul 13 23:51:29 2008
> +++ linux-2.6.26/kernel/sysctl.c Thu Sep 18 10:08:47 2008
> @@ -63,6 +63,7 @@ static int deprecated_sysctl_warning(str
> /* External variables not in a header file. */
> extern int C_A_D;
> extern int print_fatal_signals;
> +extern int signal_log_level;
> extern int sysctl_overcommit_memory;
> extern int sysctl_overcommit_ratio;
> extern int sysctl_panic_on_oom;
> @@ -398,6 +428,14 @@ static struct ctl_table kern_table[] = {
> .ctl_name = CTL_UNNUMBERED,
> .procname = "print-fatal-signals",
> .data = &print_fatal_signals,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = &proc_dointvec,
> + },
> + {
> + .ctl_name = CTL_UNNUMBERED,
> + .procname = "signal-log-level",
> + .data = &signal_log_level,
> .maxlen = sizeof(int),
> .mode = 0644,
> .proc_handler = &proc_dointvec,
> diff -u -r linux-2.6.26.vanilla/Documentation/sysctl/kernel.txt linux-2.6.26/Documentation/sysctl/kernel.txt
> --- linux-2.6.26.vanilla/Documentation/sysctl/kernel.txt Sun Jul 13 23:51:29 2008
> +++ linux-2.6.26/Documentation/sysctl/kernel.txt Thu Sep 18 10:50:13 2008
> @@ -47,6 +47,7 @@
> - rtsig-max
> - rtsig-nr
> - sem
> +- signal-log-level
> - sg-big-buff [ generic SCSI device (sg) ]
> - shmall
> - shmmax [ sysv ipc ]
> @@ -349,6 +350,21 @@
>
> ==============================================================
>
> +signal-log-level:
> +
> +Brief logging of signal and sender to aid
> +tracing of obsucure problems later on.
^^^^^^^^
> +
> + 0 - Signal logging disabled
> +
> + 1 - Log SIGSEGV, SIGILL, SIGBUS and SIGPFE (default)
^^^^^^
> +
> + 2 - Log SIGKILL and SIGABRT and all signals from log level 1
> +
> + 3 or higher: Log all signals
> +
> +==============================================================
> +
> softlockup_thresh:
>
> This value can be used to lower the softlockup tolerance
>
>
When fix typos you can add:
Reviewed-by: Marcin Slusarz <marcin.slusarz@...il.com>
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