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Date: Mon, 28 Jan 2019 09:49:59 +0100
From: Vincent Whitchurch <vincent.whitchurch@...s.com>
To: akpm@...ux-foundation.org
Cc: mcgrof@...nel.org, keescook@...omium.org,
linux-kernel@...r.kernel.org, Vincent Whitchurch <rabinv@...s.com>
Subject: [PATCH v2] sysctl: Add panic-fatal-signals
Add a sysctl which asks the kernel to panic when any userspace process
receives a fatal signal which would trigger a core dump. This has
proven to be quite useful when debugging problems seen during testing of
embedded systems: When combined with kernel core dumps (saved due to
the panic), it allows easier debugging of crashes which have their
origin in system-wide problems such as buggy drivers or other kernel or
hardware-related issues.
The crashing process's core dump can be extracted from the kernel core
dump using tools such as the crash utility's gcore extension.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
v2: Put the sysctl behind a config option
include/linux/signal.h | 1 +
init/Kconfig | 14 ++++++++++++++
kernel/signal.c | 5 ++++-
kernel/sysctl.c | 9 +++++++++
4 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/linux/signal.h b/include/linux/signal.h
index cc7e2c1cd444..109efd1432e9 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -10,6 +10,7 @@ struct task_struct;
/* for sysctl */
extern int print_fatal_signals;
+extern int panic_fatal_signals;
static inline void copy_siginfo(kernel_siginfo_t *to,
const kernel_siginfo_t *from)
diff --git a/init/Kconfig b/init/Kconfig
index d47cb77a220e..875442f6ab53 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1242,6 +1242,20 @@ config SYSCTL_SYSCALL
If unsure say N here.
+config SYSCTL_PANIC_FATAL_SIGNALS
+ bool "panic-fatal-signals sysctl" if EXPERT
+ depends on PROC_SYSCTL
+ help
+ If you say Y here, a kernel.panic-fatal-signals sysctl will be
+ offered. If this sysctl is turned on, the kernel will panic if any
+ userspace process receives a fatal signal which would trigger a core
+ dump.
+
+ When used together with kernel core dumps, this can be useful for
+ debugging some system-wide problems, primarily on embedded systems.
+
+ If unsure, say N.
+
config FHANDLE
bool "open by fhandle syscalls" if EXPERT
select EXPORTFS
diff --git a/kernel/signal.c b/kernel/signal.c
index e1d7ad8e6ab1..83c6877b0182 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -59,6 +59,7 @@
static struct kmem_cache *sigqueue_cachep;
int print_fatal_signals __read_mostly;
+int panic_fatal_signals __read_mostly;
static void __user *sig_handler(struct task_struct *t, int sig)
{
@@ -2497,8 +2498,10 @@ bool get_signal(struct ksignal *ksig)
current->flags |= PF_SIGNALED;
if (sig_kernel_coredump(signr)) {
- if (print_fatal_signals)
+ if (print_fatal_signals || panic_fatal_signals)
print_fatal_signal(ksig->info.si_signo);
+ if (panic_fatal_signals)
+ panic("Fatal signal and panic_fatal_signals=1");
proc_coredump_connector(current);
/*
* If it was able to dump core, this kills all
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ba4d9e85feb8..48023bad5b08 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -557,6 +557,15 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
+#ifdef CONFIG_SYSCTL_PANIC_FATAL_SIGNALS
+ {
+ .procname = "panic-fatal-signals",
+ .data = &panic_fatal_signals,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+#endif
#ifdef CONFIG_SPARC
{
.procname = "reboot-cmd",
--
2.20.0
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