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| author | Thomas Gleixner <tglx@linutronix.de> | 2019-04-14 19:51:06 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-04-14 23:05:52 +0200 |
| commit | 2f5fb19341883bb6e37da351bc3700489d8506a7 (patch) | |
| tree | 7773a842ba67a344b4b4da5aff530404f140571d | |
| parent | 40fba00ffa431c8597ca785ea1cfa4d9f6503390 (diff) | |
| download | linux-2f5fb19341883bb6e37da351bc3700489d8506a7.tar.gz linux-2f5fb19341883bb6e37da351bc3700489d8506a7.tar.bz2 linux-2f5fb19341883bb6e37da351bc3700489d8506a7.zip | |
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
| -rw-r--r-- | arch/x86/kernel/process.c | 8 |
1 files 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 */ |