linux-kernel - [tip:x86/urgent] x86, hotplug: Serialize CPU hotplug to avoid bringup concurrency issues

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-d7c53c9e822a4fefa13a0cae76f3190bfd0d5c11@git.kernel.org>
Date:	Thu, 19 Aug 2010 22:58:03 GMT
From:	tip-bot for Borislav Petkov <bp@...64.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	bp@...64.org, stable@...nel.org, tglx@...utronix.de,
	hpa@...ux.intel.com, borislav.petkov@....com
Subject: [tip:x86/urgent] x86, hotplug: Serialize CPU hotplug to avoid bringup concurrency issues

Commit-ID:  d7c53c9e822a4fefa13a0cae76f3190bfd0d5c11
Gitweb:     http://git.kernel.org/tip/d7c53c9e822a4fefa13a0cae76f3190bfd0d5c11
Author:     Borislav Petkov <bp@...64.org>
AuthorDate: Thu, 19 Aug 2010 20:10:29 +0200
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Thu, 19 Aug 2010 14:47:43 -0700

x86, hotplug: Serialize CPU hotplug to avoid bringup concurrency issues

When testing cpu hotplug code on 32-bit we kept hitting the "CPU%d:
Stuck ??" message due to multiple cores concurrently accessing the
cpu_callin_mask, among others.

Since these codepaths are not protected from concurrent access due to
the fact that there's no sane reason for making an already complex
code unnecessarily more complex - we hit the issue only when insanely
switching cores off- and online - serialize hotplugging cores on the
sysfs level and be done with it.

[ v2.1: fix !HOTPLUG_CPU build ]

Cc: <stable@...nel.org>
Signed-off-by: Borislav Petkov <borislav.petkov@....com>
LKML-Reference: <20100819181029.GC17171@...ab>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 arch/x86/Kconfig          |    5 +++++
 arch/x86/kernel/smpboot.c |   19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a84fc34..ac7827f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -245,6 +245,11 @@ config ARCH_HWEIGHT_CFLAGS
 
 config KTIME_SCALAR
 	def_bool X86_32
+
+config ARCH_CPU_PROBE_RELEASE
+	def_bool y
+	depends on HOTPLUG_CPU
+
 source "init/Kconfig"
 source "kernel/Kconfig.freezer"
 
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index abf4a86..8b3bfc4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -90,6 +90,25 @@ DEFINE_PER_CPU(int, cpu_state) = { 0 };
 static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
 #define get_idle_for_cpu(x)      (per_cpu(idle_thread_array, x))
 #define set_idle_for_cpu(x, p)   (per_cpu(idle_thread_array, x) = (p))
+
+/*
+ * We need this for trampoline_base protection from concurrent accesses when
+ * off- and onlining cores wildly.
+ */
+static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex);
+
+void cpu_hotplug_driver_lock()
+{
+        mutex_lock(&x86_cpu_hotplug_driver_mutex);
+}
+
+void cpu_hotplug_driver_unlock()
+{
+        mutex_unlock(&x86_cpu_hotplug_driver_mutex);
+}
+
+ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; }
+ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; }
 #else
 static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
 #define get_idle_for_cpu(x)      (idle_thread_array[(x)])
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/