From: Vladimir Kondratiev <vladimir.kondratiev@linux.intel.com>
To: Jonathan Corbet <corbet@lwn.net>,
Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Randy Dunlap <rdunlap@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
"Guilherme G. Piccoli" <gpiccoli@canonical.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Kars Mulder <kerneldev@karsmulder.nl>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Kishon Vijay Abraham I <kishon@ti.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
Joe Perches <joe@perches.com>, Rafael Aquini <aquini@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
Alexei Starovoitov <ast@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Michel Lespinasse <walken@google.com>,
Jann Horn <jannh@google.com>, chenqiwu <chenqiwu@xiaomi.com>,
Minchan Kim <minchan@kernel.org>,
Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Vladimir Kondratiev <vladimir.kondratiev@linux.intel.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: [RFC PATCH v2] do_exit(): panic() recursion detected
Date: Mon, 7 Dec 2020 14:44:33 +0200 [thread overview]
Message-ID: <20201207124433.4017265-1-vladimir.kondratiev@linux.intel.com> (raw)
Recursive do_exit() is symptom of compromised kernel integrity.
For safety critical systems, it may be better to
panic() in this case to minimize risk.
Signed-off-by: Vladimir Kondratiev <vladimir.kondratiev@linux.intel.com>
Change-Id: I42f45900a08c4282c511b05e9e6061360d07db60
---
Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
include/linux/kernel.h | 1 +
kernel/exit.c | 7 +++++++
kernel/sysctl.c | 9 +++++++++
4 files changed, 23 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 44fde25bb221..6e12a6804557 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3508,6 +3508,12 @@
bit 4: print ftrace buffer
bit 5: print all printk messages in buffer
+ panic_on_exit_recursion
+ panic() when do_exit() recursion detected, rather then
+ try to stay running whenever possible.
+ Useful on safety critical systems; re-entry in do_exit
+ is a symptom of compromised kernel integrity.
+
panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
Format: <hex>[,nousertaint]
Hexadecimal bitmask representing the set of TAINT flags
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2f05e9128201..5afb20534cb2 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -539,6 +539,7 @@ extern int sysctl_panic_on_rcu_stall;
extern int sysctl_panic_on_stackoverflow;
extern bool crash_kexec_post_notifiers;
+extern int panic_on_exit_recursion;
/*
* panic_cpu is used for synchronizing panic() and crash_kexec() execution. It
diff --git a/kernel/exit.c b/kernel/exit.c
index 1f236ed375f8..162799a8b539 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -68,6 +68,9 @@
#include <asm/unistd.h>
#include <asm/mmu_context.h>
+int panic_on_exit_recursion __read_mostly;
+core_param(panic_on_exit_recursion, panic_on_exit_recursion, int, 0644);
+
static void __unhash_process(struct task_struct *p, bool group_dead)
{
nr_threads--;
@@ -757,6 +760,10 @@ void __noreturn do_exit(long code)
*/
if (unlikely(tsk->flags & PF_EXITING)) {
pr_alert("Fixing recursive fault but reboot is needed!\n");
+ if (panic_on_exit_recursion)
+ panic("Recursive do_exit() detected in %s[%d]\n",
+ current->comm, task_pid_nr(current));
+
futex_exit_recursive(tsk);
set_current_state(TASK_UNINTERRUPTIBLE);
schedule();
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index afad085960b8..bb397fba2c42 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2600,6 +2600,15 @@ static struct ctl_table kern_table[] = {
.extra2 = &one_thousand,
},
#endif
+ {
+ .procname = "panic_on_exit_recursion",
+ .data = &panic_on_exit_recursion,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
{
.procname = "panic_on_warn",
.data = &panic_on_warn,
--
2.27.0
next reply other threads:[~2020-12-07 12:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 12:44 Vladimir Kondratiev [this message]
2020-12-07 12:52 ` [RFC PATCH v2] do_exit(): panic() recursion detected Vladimir Kondratiev
2020-12-07 15:49 ` Eric W. Biederman
2020-12-07 16:19 ` Vladimir Kondratiev
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