From: tip-bot for Frederic Weisbecker <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: cmetcalf@ezchip.com, riel@redhat.com, peterz@infradead.org,
davej@redhat.com, schwidefsky@de.ibm.com, hpa@zytor.com,
oleg@redhat.com, mingo@kernel.org, tglx@linutronix.de,
fweisbec@gmail.com, paulmck@linux.vnet.ibm.com, bp@alien8.de,
umgwanakikbuti@gmail.com, linux-kernel@vger.kernel.org,
rafael.j.wysocki@intel.com
Subject: [tip:timers/nohz] context_tracking: Protect against recursion
Date: Thu, 7 May 2015 04:31:12 -0700 [thread overview]
Message-ID: <tip-aed5ed47724f6a7453fa62e3c90f3cee93edbfe3@git.kernel.org> (raw)
In-Reply-To: <1430928266-24888-2-git-send-email-fweisbec@gmail.com>
Commit-ID: aed5ed47724f6a7453fa62e3c90f3cee93edbfe3
Gitweb: http://git.kernel.org/tip/aed5ed47724f6a7453fa62e3c90f3cee93edbfe3
Author: Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Wed, 6 May 2015 18:04:23 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 7 May 2015 12:02:50 +0200
context_tracking: Protect against recursion
Context tracking recursion can happen when an exception triggers
in the middle of a call to a context tracking probe.
This special case can be caused by vmalloc faults. If an access
to a memory area allocated by vmalloc happens in the middle of
context_tracking_enter(), we may run into an endless fault loop
because the exception in turn calls context_tracking_enter()
which faults on the same vmalloc'ed memory, triggering an
exception again, etc...
Some rare crashes have been reported so lets protect against
this with a recursion counter.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430928266-24888-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/context_tracking_state.h | 1 +
kernel/context_tracking.c | 29 +++++++++++++++++++++++++++++
2 files changed, 30 insertions(+)
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 6b7b96a..678ecdf 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -12,6 +12,7 @@ struct context_tracking {
* may be further optimized using static keys.
*/
bool active;
+ int recursion;
enum ctx_state {
CONTEXT_KERNEL = 0,
CONTEXT_USER,
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 72d59a1..5b11a10 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -38,6 +38,25 @@ void context_tracking_cpu_set(int cpu)
}
}
+static bool context_tracking_recursion_enter(void)
+{
+ int recursion;
+
+ recursion = __this_cpu_inc_return(context_tracking.recursion);
+ if (recursion == 1)
+ return true;
+
+ WARN_ONCE((recursion < 1), "Invalid context tracking recursion value %d\n", recursion);
+ __this_cpu_dec(context_tracking.recursion);
+
+ return false;
+}
+
+static void context_tracking_recursion_exit(void)
+{
+ __this_cpu_dec(context_tracking.recursion);
+}
+
/**
* context_tracking_enter - Inform the context tracking that the CPU is going
* enter user or guest space mode.
@@ -75,6 +94,9 @@ void context_tracking_enter(enum ctx_state state)
WARN_ON_ONCE(!current->mm);
local_irq_save(flags);
+ if (!context_tracking_recursion_enter())
+ goto out_irq_restore;
+
if ( __this_cpu_read(context_tracking.state) != state) {
if (__this_cpu_read(context_tracking.active)) {
/*
@@ -105,6 +127,8 @@ void context_tracking_enter(enum ctx_state state)
*/
__this_cpu_write(context_tracking.state, state);
}
+ context_tracking_recursion_exit();
+out_irq_restore:
local_irq_restore(flags);
}
NOKPROBE_SYMBOL(context_tracking_enter);
@@ -139,6 +163,9 @@ void context_tracking_exit(enum ctx_state state)
return;
local_irq_save(flags);
+ if (!context_tracking_recursion_enter())
+ goto out_irq_restore;
+
if (__this_cpu_read(context_tracking.state) == state) {
if (__this_cpu_read(context_tracking.active)) {
/*
@@ -153,6 +180,8 @@ void context_tracking_exit(enum ctx_state state)
}
__this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
}
+ context_tracking_recursion_exit();
+out_irq_restore:
local_irq_restore(flags);
}
NOKPROBE_SYMBOL(context_tracking_exit);
next prev parent reply other threads:[~2015-05-07 11:32 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-06 16:04 [GIT PULL] nohz: A few improvements v4 Frederic Weisbecker
2015-05-06 16:04 ` [PATCH 1/4] context_tracking: Protect against recursion Frederic Weisbecker
2015-05-07 9:58 ` Ingo Molnar
2015-05-07 11:53 ` Frederic Weisbecker
2015-05-07 11:31 ` tip-bot for Frederic Weisbecker [this message]
2015-05-06 16:04 ` [PATCH 2/4] context_tracking: Inherit TIF_NOHZ through forks instead of context switches Frederic Weisbecker
2015-05-07 11:31 ` [tip:timers/nohz] " tip-bot for Frederic Weisbecker
2015-05-06 16:04 ` [PATCH 3/4] nohz: Add tick_nohz_full_add_cpus_to() API Frederic Weisbecker
2015-05-07 11:31 ` [tip:timers/nohz] " tip-bot for Chris Metcalf
2015-05-06 16:04 ` [PATCH 4/4] nohz: Set isolcpus when nohz_full is set Frederic Weisbecker
2015-05-07 11:32 ` [tip:timers/nohz] " tip-bot for Chris Metcalf
2015-05-16 19:39 ` [PATCH 4/4] " Sasha Levin
2015-05-17 5:30 ` Mike Galbraith
2015-05-18 2:17 ` Rik van Riel
2015-05-18 3:29 ` Mike Galbraith
2015-05-18 14:07 ` Rik van Riel
2015-05-18 14:22 ` Mike Galbraith
2015-05-18 14:52 ` Rik van Riel
2015-05-19 2:30 ` Mike Galbraith
2015-06-12 19:12 ` Rik van Riel
2015-05-20 20:38 ` Afzal Mohammed
2015-05-20 21:00 ` Paul E. McKenney
2015-05-21 12:12 ` Afzal Mohammed
2015-05-21 12:57 ` Paul E. McKenney
2015-05-21 13:06 ` Frederic Weisbecker
2015-05-21 13:27 ` Paul E. McKenney
2015-05-21 13:29 ` Afzal Mohammed
2015-05-21 14:14 ` Paul E. McKenney
2015-05-21 14:46 ` Frederic Weisbecker
2015-05-21 18:59 ` Mike Galbraith
2015-05-22 14:39 ` Frederic Weisbecker
2015-05-22 15:20 ` Mike Galbraith
-- strict thread matches above, loose matches on Subject: below --
2015-04-03 16:24 [PATCH 1/2] nohz: add tick_nohz_full_set_cpus() API cmetcalf
2015-04-03 16:24 ` [PATCH 2/2] nohz: make nohz_full imply isolcpus cmetcalf
2015-04-03 17:42 ` Frederic Weisbecker
2015-04-03 19:20 ` Chris Metcalf
2015-04-04 14:10 ` Rik van Riel
2015-04-04 17:09 ` Chris Metcalf
2015-04-05 5:05 ` Ingo Molnar
2015-04-06 17:15 ` Chris Metcalf
2015-04-06 18:16 ` [PATCH v2 1/2] nohz: add tick_nohz_full_clear_cpus() and _set_cpus() APIs cmetcalf
2015-04-06 18:16 ` [PATCH v2 2/2] nohz: make nohz_full imply isolcpus cmetcalf
2015-04-07 22:29 ` Frederic Weisbecker
2015-04-08 9:41 ` Peter Zijlstra
2015-04-08 14:04 ` Chris Metcalf
2015-04-08 14:26 ` Peter Zijlstra
2015-04-08 15:21 ` Chris Metcalf
2015-04-08 17:24 ` Frederic Weisbecker
2015-04-08 19:20 ` [PATCH v3 1/2] nohz: add tick_nohz_full_clear_cpus() and _set_cpus() APIs cmetcalf
2015-04-08 19:20 ` [PATCH v3 2/2] nohz: set isolcpus when nohz_full is set cmetcalf
2015-04-08 17:27 ` [PATCH v2 2/2] nohz: make nohz_full imply isolcpus Peter Zijlstra
2015-04-08 18:12 ` Chris Metcalf
2015-04-09 8:29 ` Peter Zijlstra
2015-04-09 12:02 ` Chris Metcalf
2015-04-09 12:45 ` Frederic Weisbecker
2015-04-09 16:59 ` [PATCH v5] nohz: set isolcpus when nohz_full is set Chris Metcalf
2015-04-09 17:12 ` Peter Zijlstra
2015-04-10 1:05 ` Mike Galbraith
2015-04-10 15:33 ` Chris Metcalf
2015-04-10 15:57 ` Mike Galbraith
2015-04-09 17:00 ` [PATCH v4 1/2] nohz: add tick_nohz_full_cpumask_or() and _andnot() APIs Chris Metcalf
2015-04-09 17:00 ` [PATCH v4 2/2] nohz: set isolcpus when nohz_full is set Chris Metcalf
2015-04-09 17:07 ` [PATCH v4 1/2] nohz: add tick_nohz_full_cpumask_or() and _andnot() APIs Peter Zijlstra
2015-04-09 17:24 ` Chris Metcalf
2015-04-09 17:42 ` Peter Zijlstra
2015-04-09 18:01 ` [PATCH v6 1/2] nohz: add tick_nohz_full_add_cpus_to() and _remove_cpus_from() APIs Chris Metcalf
2015-04-09 18:01 ` [PATCH v6 2/2] nohz: set isolcpus when nohz_full is set Chris Metcalf
2015-04-10 1:37 ` Frederic Weisbecker
2015-04-10 20:53 ` [PATCH v7 1/2] nohz: add tick_nohz_full_add_cpus_to() and _remove_cpus_from() APIs Chris Metcalf
2015-04-10 20:53 ` [PATCH v7 2/2] nohz: set isolcpus when nohz_full is set Chris Metcalf
2015-04-14 0:37 ` Frederic Weisbecker
2015-04-14 15:17 ` [PATCH v8 1/2] nohz: add tick_nohz_full_add_cpus_to() API Chris Metcalf
2015-04-14 15:17 ` [PATCH v8 2/2] nohz: set isolcpus when nohz_full is set Chris Metcalf
2015-04-14 15:26 ` Frederic Weisbecker
2015-04-14 16:45 ` Peter Zijlstra
2015-04-14 0:33 ` [PATCH v7 1/2] nohz: add tick_nohz_full_add_cpus_to() and _remove_cpus_from() APIs Frederic Weisbecker
2015-04-14 0:49 ` Chris Metcalf
2015-04-14 15:34 ` Frederic Weisbecker
2015-04-10 1:34 ` [PATCH v6 " Frederic Weisbecker
2015-04-10 15:31 ` Chris Metcalf
2015-04-06 18:29 ` [PATCH v2 1/2] nohz: add tick_nohz_full_clear_cpus() and _set_cpus() APIs Frederic Weisbecker
2015-04-06 19:09 ` Chris Metcalf
2015-04-07 9:33 ` Ingo Molnar
2015-04-03 18:08 ` [PATCH 2/2] nohz: make nohz_full imply isolcpus Mike Galbraith
2015-04-03 19:21 ` Chris Metcalf
2015-04-04 2:03 ` Mike Galbraith
2015-04-04 3:43 ` Mike Galbraith
2015-04-06 19:28 ` Rik van Riel
2015-04-07 3:10 ` Mike Galbraith
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