From: tip-bot for Thomas Gleixner <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, mingo@kernel.org,
mikhail.v.gavrilov@gmail.com, thomas.lendacky@amd.com,
hpa@zytor.com, linux-kernel@vger.kernel.org
Subject: [tip:x86/urgent] x86/speculation: Prevent deadlock on ssb_state::lock
Date: Sun, 14 Apr 2019 14:10:06 -0700 [thread overview]
Message-ID: <tip-2f5fb19341883bb6e37da351bc3700489d8506a7@git.kernel.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1904141948200.4917@nanos.tec.linutronix.de>
Commit-ID: 2f5fb19341883bb6e37da351bc3700489d8506a7
Gitweb: https://git.kernel.org/tip/2f5fb19341883bb6e37da351bc3700489d8506a7
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Sun, 14 Apr 2019 19:51:06 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 14 Apr 2019 23:05:52 +0200
x86/speculation: Prevent deadlock on ssb_state::lock
Mikhail reported a lockdep splat related to the AMD specific ssb_state
lock:
CPU0 CPU1
lock(&st->lock);
local_irq_disable();
lock(&(&sighand->siglock)->rlock);
lock(&st->lock);
<Interrupt>
lock(&(&sighand->siglock)->rlock);
*** DEADLOCK ***
The connection between sighand->siglock and st->lock comes through seccomp,
which takes st->lock while holding sighand->siglock.
Make sure interrupts are disabled when __speculation_ctrl_update() is
invoked via prctl() -> speculation_ctrl_update(). Add a lockdep assert to
catch future offenders.
Fixes: 1f50ddb4f418 ("x86/speculation: Handle HT correctly on AMD")
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1904141948200.4917@nanos.tec.linutronix.de
---
arch/x86/kernel/process.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 58ac7be52c7a..957eae13b370 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -426,6 +426,8 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
u64 msr = x86_spec_ctrl_base;
bool updmsr = false;
+ lockdep_assert_irqs_disabled();
+
/*
* If TIF_SSBD is different, select the proper mitigation
* method. Note that if SSBD mitigation is disabled or permanentely
@@ -477,10 +479,12 @@ static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
void speculation_ctrl_update(unsigned long tif)
{
+ unsigned long flags;
+
/* Forced update. Make sure all relevant TIF flags are different */
- preempt_disable();
+ local_irq_save(flags);
__speculation_ctrl_update(~tif, tif);
- preempt_enable();
+ local_irq_restore(flags);
}
/* Called from seccomp/prctl update */
prev parent reply other threads:[~2019-04-14 21:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-02 18:33 [5.0.0 rc3 BUG] possible irq lock inversion dependency detected Mikhail Gavrilov
2019-04-14 17:33 ` Mikhail Gavrilov
2019-04-14 17:51 ` Thomas Gleixner
2019-04-14 20:07 ` Mikhail Gavrilov
2019-04-18 16:52 ` Mikhail Gavrilov
2019-04-18 19:17 ` Thomas Gleixner
2019-04-14 21:10 ` tip-bot for Thomas Gleixner [this message]
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